Gas/Fuel vapors/fumes visible from gas door

[ElJayBird]

The reason fuel lines get brought up is our trucks use a fuel pressure regulator that flows the excess fuel back to the tank, and during its trip up to the engine compartment and through the rails the fuel gets quite hot. This thermal energy is just dumped back into the tank increasing the temp of the fuel beyond ambient.. or ambient plus all the heat under the rig.

If the fuel were cooled before getting back to the tank this would eliminate a major btu source.

This is a lesson the OEMs know well, and have made design decisions around, even if for different reasons than we are discussing. Some vehicles (the 2008 Escalade my L92 came from comes to mind) use a returnless fuel system partly to simplify plumbing and safety but primarily to reduce heat return to the tank which drastically reduces evaporative emissions.

Ah - that makes sense. Thanks for the education

 

[TeCKis300]

From a systems design perspective, a returnless fuel system is generally a lower end architecture. Toyota does use them in lower end models. They have their own cons. In regards to heat, is not a solution, because in low speed crawling conditions, the fuel sitting longer in the rail waiting to be injected will become super heated. Pair that with super heated intake air and that can create performance issues. With the added possibility of vapor lock which use to be very common in cars.

 

[bloc]

From a systems design perspective, a returnless fuel system is generally a lower end architecture. Toyota does use them in lower end models. They have their own cons. In regards to heat, is not a solution, because in low speed crawling conditions, the fuel sitting longer in the rail waiting to be injected will become super heated. Pair that with super heated intake air and that can create performance issues. With the added possibility of vapor lock which use to be very common in cars.

Totally makes sense Toyota would put the most costly but better performing system on this platform. It still has some clear drawbacks as this whole thread shows.

 

[TeCKis300]

Since I'll be playing with the fuel tank this weekend, might do some preventative heat mitigation efforts.

Amazon product ASIN B096RW16L9

 

[2001LC]

I’m gonna say something that I’ve been working on for over a year now. It will not be received positively from the community. But please, understand that I’ve been taking measurements across over 80 200s under lot of conditions. It took me a long time to even accept this as I just didn’t feel the failure was what I “wanted to believe.”

Also, don’t take what I say as gospel, I would like to be proved wrong here. It frustrate me a lot on what I believe the issue is.

What I’ve found, is the following. Let go of anything aftermarket causing fuel boiling. Just let it go, it’s not the culprit. 200s have been boiling fuel long before most things were even available for our trucks. Elevation doesn’t necessarily matter. Ambient temp doesn’t necessarily matter. Fuel type and octane equivalent levels doesn’t necessarily matter. Emissions equipment doesn’t matter. Age sometimes matters, but I’ve seen plenty of brand new, bone stock 200s boil gas when off road or towing.

Toyota uses a return style fuel system. Just like on the 4.7L, Toyota found that it was best to run the fuel pump wide open. Then uses a fuel pressure regulator to manage the fuel needed for the motor. The extra goes back to the tank. BUT!!! This is where it gets interesting. They use the extra fuel to cool various components on the top end of the motor. Fuel is a hell of a cooling liquid and Toyota uses it, along with engine oil and coolant to keep their V8s from ever over heating.

So… when you are applying a lot of load on the engine, it is going to run hotter. You are now sending hotter fuel back to the tank. After awhile, you will raise the fuel temperature of the tank to where it will boil. Fuel only needs very low 110ish°F to boil. And higher octane fuels have lower boiling points, so that isn’t helping. Detonatates higher, but boils lower. Anyway, can now boil away in the tank, but still not cause vapor lock like on old carbureted motor due to their pretty well designed pressure regulator and pumps that can still flow boil liquors good enough to never mess with a perfectly running 5.7.

I’ve plopped temp sensors in tank, in line on the send and return lines, and it pretty clear that the 150° fuel returning to the tank is raising the tank temp level. Auxiliary fuel tanks, engine bays loaded with batteries, aftermarket bumpers, skid plates, big tires, roof racks with massive RTTs, it doesn’t matter. This is a deeper problem.

So I feel from my findings building these trucks that, ugh… it pains me to say this.

Toyota F’ed up.

They put so much emphasis on keeping the engine cool, that they forgot about the stuff behind it. Toyota can put in 2 transmission coolers, one engine cooler, steering cooler (which is legit because I broke my Tacoma rack due solely to heat) but they needed to put a cooler for the fuel.

I’m heavy into other Toyota forums from BudBuilt, and the Tundra guys with 5.7s also are plentiful with fuel boiling statements. And if you didn’t know, under those trucks, it’s wide open with space, but they still boil. Because it’s not about crap around the truck, it’s about the motor and fuel system itself.

The 4.0, both single and duel VVT-I and the 3.5 bit have very little reports of boiling fuel. From tuning my own 4.0, how Toyota ran the fuel back to the tank on those, it did not have to cool as much and the way back to the tank. I personally melted a stock resin fuel tank skid on my FJ from exhaust heat. Just melted it like a grilled cheese, but NEVER boiled fuel, or head about anyone boiling fuel then. But have always heard about it from 100 series guys. In Iraq, I ran a lot of 100s and 200s with gas motors (they worked better for our needs than the diesels, that and I blew a lot of turbos and needs more reliability) we boiled fuel all the time. I just had many other things I cared about at the time.

So that’s it guys. Our precious, should be the most perfectly engineered vehicles of all time, is not perfect. Toyota should of managed fuel heat, they didn’t. I have been working on a solution, but honestly, at this point, I’d rather help everyone with knowledge than providing a future solution. We just need to cool the fuel. It’s not hard, it doesn’t hurt reliability (as I know that will be the next thing that most of us won’t be able to accept) it just needs a simple cooler in a good spot. I’ve played with the concept already, and proved that it works. What I haven’t done is made a good kit for it to be plug and play.

So that’s my story guys. On this particulate issue, we need to become Jeep and Land Rover enthusiast, and fix what the factory failed to do in the first place. It’s hard to accept, I’ve personally lost months of sleep over this.

Some extra reading on data points if you want them. I e found that under racing conditions, it’s hard to boil fuel. The reason is because most of the fuel is consumed, and air flow over the top of the motor is high. Remember, there is now factory air flow under the motor, but that’s not the problem, it’s cooling if the top end, and heat rises. High load, and no wind, that builds heat, but uses little fuel, and little cooling from air being literally rammed through the engine bay. Which is off roading or slow towing. LCDC ‘19, I watched two separate 200s with nothing more than all terrain tires boil some serious fuel. I also saw one 200 with a lift and slider boil, and a super built 200 with freaking everything boil. They all did it when off roading. Have air vents won’t help a thing, because heat rises. The air cooling only helps when air is being forced right through the grill over the top of the motor, that it, it has nothing to do with heat down low off differentials or exhaust. I personably have a Jet-Hot coated headers to muffler that cuts radiant heat over 50%. That. It advertised, that real life testing I did. Guess what, didn’t do a damn thing for fuel temps.

Best thing to mirage right now. Don’t ever open your fuel cap, even if you see fuel boiling out. Just like your radiator, pressure raises boiling points. So keep the cap on, unless you like to lower you fuel’s boiling point even lower. Then, turn your engine off. No more fuel running over a hot motor, it then cools very very quickly. Wheeling with people who s*** their 5.7s off a lot seem to never boil. Those who run in low range constantly and leave this motors running when stopping to access the trail, seem to boil much more regularly. Also, as the motor itself gets older, it runs hotter, just how it works, so while I’ve seen more sub 5,000 mile 5.7s boil fuel, it can happen more when they get up there in mileage. Another thing I’ve found it people adding aftermarket wiring to the engine room (the technical term for the fuse box) I’ve seen that play havoc with the fuel delivery and air injection systems cause the motor to run hotter, which as a side affect, boils gas.

I've no doubt @Taco2Cruiser, is correct. In that fuel on it's journey from gas tank to fuel rail and back to tank, picks up heat. That most of the heat comes from engine compartment. A fuel cooler would certainly benefit every fuel boil vehicle. It would be simpler than wrapping all fuel lines with heat shield and likely work much better.

What I find socking here in the 200 and in the 100 series tech sections, on fuel boil related threads. Seems almost no one is monitoring Fuel Trims (FT), Engine Coolant Temp (ECT), intake air temp (IAT) and Automatic Transmission temps (AT Temp) or CAT temp 2006-up. Number one thing I've done to correct fuel boiling in 100 series, is get ECT down to where it should be.

The fuel on it's journey:
First picks up heat form fuel pump.
Second fuel tank from radiant road and air heat.
Third fuel line to engine, picks up heat from road, air, transmission ( note:200 series AT run much hotter than 100 series) and CAT/exhaust pipe.
Fourth engine radiant heat.
Than the journey back to fuel tank. Passing and picking up heat from the same sources.

That a fully built heavy armored up. Will retain much more of this heat. Add in slow, low gear on rough dusty terrain. With air filled with , bugs, grasses, weeds, cotton, etc. to clog radiator fins. They will run the hottest ECT, AT & IAT. What the temps are, is key.

I seen many example of fully built and stock 100 series, that do not boil fuel. One very built 07LC, that comes to mind. Is used from coast to coast in the most demanding off road condition our rigs ever see. From Sea level to above tree line (12,500 ft ASL) with OAT -20F to 110F. Now has ~120K miles on the odometer. It has never boiled fuel.

I can't seem to say this enough. Get basics inline staring with coolant system. Which number one issue I find in 99 out of 100 vehicles, which is causing high ECT. Radiator fins are clogged with debris!

Read your OM. It states: Wash your radiator fins. Getting your engine temp down, goes a long way in reduce fuel temp. I drop ECT on the average 20F, just clean the fins of the 3 radiators. This also drop AT temp.

There is one new thing (new for me) I'm looking at. Fuel pump resistor. I've just started taking and IR temp gun, and checking FP resistor temps. I shoot the FP resistor, fender just above FP resistor, and record that data along with IAT, ECT, OAT along with weather condition (i.e: sun, overcast, noon, AM, night, rian, snow, etc.).

 

[grinchy]

Where is a likely area to plumb in a fuel cooler?

 

[linuxgod]

I'd add to your list of data points: The ECT (engine coolant temp).
I also like to run logs while driving. Have MPH & RPM is very helpful in decipher data.

All I've found boiling fuel, run hot! Most jump to over 203F just sitting (summer heat AC on) at a red light. Very often I find ECT hitting 212F+ in these fuel boiling rigs.

In a properly running 100 series, w/OAT over 80F. I find ECT ranging:
98-02: ECT 184-187F with momentary bumps to 190F in 100F OAT, full sun, stop and go traffic both AC on full cold.
03-07: ECT 194-197F with momentary bumps to 200F in 100F OAT, full sun, stop and go traffic both AC on full cold.

I’ve never seen my coolant temp exceed 203F. That includes towing 6k lbs over 11k mountain passes, and through 100F+ stretches of highway at 75+. Doing trails this week I actually found it ran lower than normal when in 4Lo and in 1st or 2nd, around 185-190. Someone else in my group had high coolant temps in the same run. I suggested maybe his radiator cap isn’t tight or else he still had some air in his system from back when he did the radiator last year. Seemed odd that two identical trucks had such a significant difference in temp…

 

[bloc]

Plus many of us have relatively low mile radiators. I don’t monitor ECTs beyond the gauge but have never seen it move above normal, not one iota. I’m thinking clogged fins aren’t the issue here. It’s fuel in the rails absorbing a ton of heat and getting sent back to the tank, which will happen independent of coolant temps.. unless maybe you replace the fan clutch with a solid block and keep the under hood temps far lower than stock.

 

[2001LC]

I’ve never seen my coolant temp exceed 203F. That includes towing 6k lbs over 11k mountain passes, and through 100F+ stretches of highway at 75+. Doing trails this week I actually found it ran lower than normal when in 4Lo and in 1st or 2nd, around 185-190. Someone else in my group had high coolant temps in the same run. I suggested maybe his radiator cap isn’t tight or else he still had some air in his system from back when he did the radiator last year. Seemed odd that two identical trucks had such a significant difference in temp…

Let's be clear: I'm not saying cleaning radiator fins will cure all fuel boiling. But we must make sure basic are in line first. Or we chase out tails. Also worth a note: Once a fuel boiling episode has happened, it become harder to cure to 100 % to no boiling events. It's believed that EVAP become damaged, is one possible reason for this.

I can't speak for the 200 series, as much as I can for 100 series. As most of my coolant work and monitoring has been on the 100 series. I just don't work on enough 200 series to get the data points needed, like @Taco2Cruiser did. And most of the 200 I do service, are daily drivers. Most coolant work I do on 200's is; PM radiators replacement, cap & hoses, water pump, thermostat and flushing. Even though I replace the rads, I still wash the other 2 radiators fins, that are in front of engine rad. But still the principle applies to all vehicle. Coolant system need to be keep at peak performance!

First in that all radiator fins become clogged. Once debris builds in them, a few things happen:
First air passages through fins are obstructed, reducing air flow. It is air flow over radiators fins and core tubes, that carries away heat.
Second the debris will cause some extra heat retention. As the ECT goes up, fuel in rails and fuel lines which includes return lines wrapping around engine intake manifold heat-up more than designed for. The hotter the engine is running (ECT is our measure of this) the more heat fuel lines absorb.

A secondary effect, is AT fluid does not cool as well. It also has it's own radiator (fins clog) and a pre-cooler in engine radiator. This than raises AT fluid temp. Which the 200 series AT fluid (in new, or normal) run closer to ~190F, whereas 100 series run ~155F. The 100 series with mildly obscured radiators. AT temp reach around 190F when pushing it on HWY at 80 MPH gearing down to run in high RPM of 5,400 (red line). Take that same 100 and clean radiator fins. AT runs around 165F in same HWY high RPM run.

Additionally: Fuel molecules expand as the fuel heats. This reduce fuel volume, which can lead to a lean fuel condition. It works the ECM harder, and tends to run engine on the lean side. Lean fuel mixture, raises cylinder head temp. Which in turn raises ECT and CAT temp. We do see a drop in CAT temps after radiator fins cleaned and driven under same condition. Cooling fuel has opposite effect. As a teenager, I had some buddies raced full stock GTO in the early 70's. They had hidden tricks to increase HP. One was a coffee can with a copper tube coiled in it. The tube was hooked in fuel delivery (inline) line. They'd fill coffee can with ice, just before the race. This would shrink fuel molecules, which would then delivery more fuel to intake ports.

Another effect of hot fuel is heat transfer to pump. Heat increase electrical resistance, and this can slow pump, reduce fuel flow. Which may be additional factor reducing furl volume to engine (lean fuel mixture).

I just bough very clean 07LX w/145K out of ABQ NM last month. In studying it's service history as a pre-inspection, before hands on inspection. I saw Lexus service history notation of hesitation while driving at times, as reported by customer. Dealership shop could not duplicate! The time of year was summer. So I assumed radiator fins clogged and was likely causing it to run to hot, resulting in some performance issues (hesitation).

In test driving around ABQ during my hands on PPI. ECT would jump to near 200F as I'd wait at a red light in full sun OAT 94F, AC off. If AC turned on, ECT would go over 205F sitting at a red light. This is one of the best indicator, radiator fins are clogged and or some other issue with coolant system.

In divining back from ABQ to Den. I was hitting ECT of 214F at OAT 91F overcast ~6PM at 5,400 RPM (red line) ~80 MPH (gear DN in 3rd). AT fliud 2 temp was hitting ~193F. AT temp in 100 series should stay around 145F to 167F. ECT should stay below 200F in 03-07 and below 190F in 98-02. So this was running hot for sure!

Once back in Denver, first thing I did was look at radiator fins (see pic below) and clean them. ECT and AT fluid temps dropped as soon as I did. But like any radiator not regularly cleaned, it needs more cleaning (a lot more). We're only about 60% effective at clean, fins with rad in place. Even radiators removed and cleaned, it's very difficult to get 100% clean and takes repeated washings.

The service history, carfax and condition of vehicle, indicates it's been 98% driven on paved roads. In South Colorado and north NM/AZ

Here's what I'd call mild debris in engine radiator fins, which in my new 07LX w/145K miles.
I see much worst on a daily basis. I sometime get two or three shovels full of muck, not including what washed down the gutter, come out of radiators fins!

Plus many of us have relatively low mile radiators. I don’t monitor ECTs beyond the gauge but have never seen it move above normal, not one iota. I’m thinking clogged fins aren’t the issue here. It’s fuel in the rails absorbing a ton of heat and getting sent back to the tank, which will happen independent of coolant temps.. unless maybe you replace the fan clutch with a solid block and keep the under hood temps far lower than stock.

I'll repeat for emphasis: Let's be clear: I'm not saying cleaning radiator fins will cure all fuel boiling. But we must make sure basic are in line first. Or we chase out tails. Also worth noting: Once a fuel boiling episode has happened, it become harder to cure to 100 % no boiling. It's believed that EVAP become damaged, is one possible reason for this.

Gauges on dash is useless especially in LC 100 series, the LX seem slightly more responsive. But neither move much, unless hitting ECT over ~240F, than still not much until overheating event. If you see a dash gauge peg HOT, your in trouble.

I use a Bluedrive and just picked up a OBDIImx+ this year. I read the ECM/CPU data from my iphone, from all sensors. Which OBDIImx+ app I use, allows AT temps monitoring also. These gives actual read outs of data from ECM/CPU and all sensors continuously. These apps, also keep logs on my iphone, which I email myself. So I can study varying condition on long or short runs.

Here a snap shot of log, from my ABQ to Den trip, just at end of running hard HWY burn. What I call a HWY burn (AKA Italian burn, AKA Italian tune). I do these HWY burns to cook/clean CAT's, A/f & o2 sensors and blow off some cylinder head carbon. See ECT at 213.8F in logs,. Dash gauge never moved from 187 to the 213.8F. But I can assure you, that over 200F is not normal. Even in stop and go high noon sun 100F OAT in the mile high city with both AC running on full cold

But clogged radiator fins are not only coolant issues I find. But they are in most every rig I inspect.

Here are some more issues I find with coolant systems:

1. Bad rad cap. Cap is designed to release pressure at 108Kpa. If it sticks, pressure in coolant system increase and so doe ECT temp. Pressure = heat!
2. Bad thermostat or installed wrong or junk aftermarket. 200 series thermostats come in a water inlet housing, so really hard to install wrong. But 100 series have a jiggle valve, which must be at top. If not at top, air will not properly purge to high point of coolant system.
3. Reservoir issues. The 200 series reservoir was redesigned, to correct some short comings. In the 100 series, I find 1 in 4 feed tubes cured up. This than suck in air during cool down.
4. Reservoir lines clogged.
5. Low coolant in system. We look at reservoir and see fluid, and think all is good. Wrong. We must check under radiator cap. Again more of issue in 100 series. But if air in any coolant system, it will not work properly. Than we often get false reading, by just looking at reservoir.
6. Wrong mix of coolant. This is never an issue in 04-up if using Toyota pink SLL pre mix 50/50. But some feel they can run 100% red Toy LL to improve cooling or lower freezing temp.... Wrong. Stick with Toy coolant and mix only as stated on container, is best. Flush often!
7. Weak fan clutch.
8. Coolant leaks.

Vacuum leaks & fuel starvation, plugs, coils, PCV, T-body and MAF cleaning, etc. Are a issue themselves, that must be brought inline. Transmission flush and with what is also important. All need brought inline with factory design. Which is what I call a tune!

I can assure you. I find a lot of 2UZ-fe running hot. In most every case I hear: "my engine runs fine, no issues". They're wrong 8 out 10 times! But the 2UZ can take a licking and just keep ticking. It is legendary.

@Taco2Cruiser mention how much corrective work he does, where others have touch with a wrench. I too do more corrective work than you can imagine. From shop you'd not believe. Many are very well known here in mud, as a great shops. I have stuff brought to me daily to correct F--ups from others. Coolant system is just one of the system, I do a lot of correcting on.

In all cases, get basic inline is so important!

But what we can not control is the weather. Hot is hot and high altitude has it's effects. That is where fuel cooler is a great idea. Rob! Let me know what you come up with. I'll use anything you design.

 

[bloc]

And still, people’s coolant temps aren’t higher than expected when this happens. Clogged fins, radiator caps, thermostat, irrelevant if the coolant temp is in the ideal range.

Plus, a damaged evap system likely isn’t lowering fuel tank pressure, it is increasing it, which should help prevent boiling.

 

[TeCKis300]

Let's be clear: I'm not saying cleaning radiator fins will cure all fuel boiling. But we must make sure basic are in line first. Or we chase out tails. Also worth a note: Once a fuel boiling episode has happened, it become harder to cure to 100 % to no boiling events. It's believed that EVAP become damaged, is one possible reason for this.

I can't speak for the 200 series, as much as I can for 100 series. As most of my coolant work and monitoring has been on the 100 series. I just don't work on enough 200 series to get the data points needed, like @Taco2Cruiser did. And most of the 200 I do service, are daily drivers. Most coolant work I do on 200's is; PM radiators replacement, cap & hoses, water pump, thermostat and flushing. Even though I replace the rads, I still wash the other 2 radiators fins, that are in front of engine rad. But still the principle applies to all vehicle. Coolant system need to be keep at peak performance!

First in that all radiator fins become clogged. Once debris builds in them, a few things happen:
First air passages through fins are obstructed, reducing air flow. It is air flow over radiators fins and core tubes, that carries away heat.
Second the debris will cause some extra heat retention. As the ECT goes up, fuel in rails and fuel lines which includes return lines wrapping around engine intake manifold heat-up more than designed for. The hotter the engine is running (ECT is our measure of this) the more heat fuel lines absorb.

A secondary effect, is AT fluid does not cool as well. It also has it's own radiator (fins clog) and a pre-cooler in engine radiator. This than raises AT fluid temp. Which the 200 series AT fluid (in new, or normal) run closer to ~190F, whereas 100 series run ~155F. The 100 series with mildly obscured radiators. AT temp reach around 190F when pushing it on HWY at 80 MPH gearing down to run in high RPM of 5,400 (red line). Take that same 100 and clean radiator fins. AT run around 165F in same HWY high RPM run.

As secondary effect is : Fuel molecules expand as the fuel heats. This reduce fuel volume, which can lead to a lean fuel condition. It works ECM harder, and tends to run engine on the lean side. Lean fuel mixture, raises cylinder head temp. Which in turn raises ECT and CAT temp. We do see a drop in CAT temps after radiator fins clean and driven under same condition. Cooling fuel has opposite effect. As a teenager, I had some buddies raced full stock GTO in the early 70's. They had hidden tricks to increase HP. One was a coffee can with a copper tube coiled in it. The tube was hooked in fuel delivery (inline) line. They'd fill coffee can with ice, just before the race. This would shrink fuel molecules as such delivery more fuel to intake ports.

Another effect of hot fuel is heat transfer to pump. Heat increase electrical resistance, and this can slow pump, reduce fuel flow.

I just bough very clean 07LX w/145K out of ABQ NW last month. In studying it's service history as a pre inspection, before hands on inspection. I saw Lexus service history notation of hesitation while driving at times, as reported by customer. Dealership shop could not duplicate. The time of year was summer. So I assumed radiator fins clogged..

In test driving around ABQ. ECT would jump to near 200F as I'd wait at a red light in full sun OAT 94F, AC off. If AC turned on, ECT would go over 205F. This is one of the best indicator fins are clogged and or some other issue with coolant system.

In divining back from ABQ to Den. I was hitting ECT of 214F at OAT 91F overcast 6PM at 5,400 RPM (red line) ~80 MPH. AT 2 temp was hitting ~193F. AT temp in 100 series should stay around 145F to 167F. ECT should stay below 200F in 03-07 and below 190F in 98-02. So this was running hot!

Once back in Denver, first thing I did was look at radiator fins and clean them. ECT and AT fluid temps dropped as soon as I did. But like any radiator not regularly cleaned, it needs more cleaning. We're only about 60% effective at clean, with rad in place. Even radiators removed and cleaned, it's very difficult to get 100% clean and takes repeated washings.

The service history, carfax and condition of vehicle, indicates it's been 98% driven on paved roads. In South Colorado and north NM/AZ

Here's what I'd call mild debris in engine radiator fins, in my new 07LX w/145K miles.
I see much worst on a daily basis. I sometime get two or three shovels full, not including what washed down the gutter, come out of radiators fins!
View attachment 3077315
View attachment 3077314


I'll repeat for emphasis: Let's be clear: I'm not saying cleaning radiator fins will cure all fuel boiling. But we must make sure basic are in line first. Or we chase out tails. Also worth noting: Once a fuel boiling episode has happened, it become harder to cure to 100 % no boiling. It's believed that EVAP become damaged, is one possible reason for this.

Gauges on dash is useless especially in LC 100 series, the LX seem slightly more responsive. But neither move much, unless hitting ECT over ~240F, than still not much until overheating event. If you see a dash gauge peg HOT, your in trouble.

I use a Bluedrive and just picked up a OBDIImx+ this year. I read the ECM?CUP data from my iphone from all sensors. Which OBDmx+ app I use, allows AT temps also. These give actual read outs of data from CPU/ECM continuously. They also keep logs on my iphone, which I email myself. So I can study varying condition on long or short runs.

Here a snap shot of log, from my trip ABQ to Den, just at end of running hard HWt burn. What I call a HWY burn (AKA Italian burn, AKA Italian tune). I do these HWY burns to cook clean CAT s, A/f & o2 sensors and blow off some cylinder head carbon. See ECT at 213.8F, gauge on dash never moved from 187 to the 213.8F. But I can assure you, that over 200F is not normal. Even in stop and go high noon sun 100F OAT in the mile high city.

View attachment 3077465

But clogged radiator fins are not only coolant issues I find. But they are in most every rig I inspect.

Here are some more issues I find with coolant systems:

1. Bad rad cap. Cap is designed to release pressure at 108Kpa. If it stick pressure in coolant system increase and so doe ECT temp.
2. Bad thermostat or installed wrong or junk aftermarket. 200 series thermostats come in a water inlet housing, so really hard to install wrong. But 100 series have a jiggle valve, which must be at top. If not air will not properly purge to high point of coolant system.
3. Reservoir issues. The 200 series reservoir was redesigned. In the 100 series, I find 1 in 4 feed tube cured up. This than suck in air during cool down
4. Reservoir lines clogged.
5. Low coolant in system. We look at reservoir and see fluid sat think all is good. Wrong. We must check under radiator cap. Again more of issue in 100 series. But if air in any coolant system, it will not work properly. Than we often get false reading, by just looking at reservoir.
6. Wrong mix of coolant. This is never an issue in 04-up if using Toyota pink SLL pre mix 50/50. But some feel they can run 100% red Toy LL to improve cooling or lower freezing temp.... Wrong. Stick with Toy coolant and mix only as stated on container, is best. Flush often!
7. Weak fan clutch.
8. Coolant leaks.

Vacuum leaks & fuel starvation, plugs, coils, PCV, T-body and MAF cleaning, etc. Are a issue themselves, that must be brought inline. Transmission flush and with what. All need brought inline with factory design.

I can assure you. I find a lot of 2UZ-fe running hot. In most every case I hear my engine runs fine, no issues. They're wrong 8 out 10 times! but the 2UZ can take a licking and just keep ticking. It is legendary.

@Taco2Cruiser mention how much corrective work he does, where others have touch with a wrench. I too do more corrective work than you can imagine. From shop you'd not believe. Many are very well known in mud, as a great shops. I have stuff brought to me daily to correct F--ups. Coolant system is just one system I do a lot of correcting on.

In all cases, get basic inline!

But what we can not control is the weather. Hot is hot and high altitude has it's effects. That is where fuel cooler is a great idea, Rob! Let me know what you come up with. I'll use anything you design.

I agree that it's worthwhile to troubleshoot basics first. We know there's multiple potential contributors. Each adding to overall heat input to the fuel system, potentially pushing it over the point of too much vapor pressure for the system to handle.

Surely this would be a variable to rule out. If not to reduce it's contribution to the problem, but increase it's assistance to keeping the problem at bay. Even if it doesn't effect ECT, this has to potential to reduce airflow from the radiator fan throughout the engine bay and into the underbody. Less airflow means increased localized heat. It's why using low range can help as it increases the relative engine speed, engine driven radiator fan RPM, and overall cooling airflow.

 

[linuxgod]

Do those with built LX570’s have boiling fuel as often as those with LC’s? I’ve found if I put 87 octane in my rotopax I have to regularly vent it if the truck sits in the hot sun or it will expand a ton and then when I vent the vapors seem to be boiling. If I fill it with 93 octane I rarely have to vent it for weeks on a trip - there’s very little vaporization.

I’ve been running 91 since I got to CO (Nebraska, actually) for the last 2 weeks and while I did have a little fuel under my fuel door and some fuel vapor smells on Red Cone I’ve (thankfully) never had any CEL lights. Did Imogene Pass today and no issues at all. I have a hunch lower octane fuel suffers from this more than higher octane though I don’t think it’s immune. But it’s just a theory at this point

 

[bloc]

Do those with built LX570’s have boiling fuel as often as those with LC’s? I’ve found if I put 87 octane in my rotopax I have to regularly vent it if the truck sits in the hot sun or it will expand a ton and then when I vent the vapors seem to be boiling. If I fill it with 93 octane I rarely have to vent it for weeks on a trip - there’s very little vaporization.

I’ve been running 91 since I got to CO (Nebraska, actually) for the last 2 weeks and while I did have a little fuel under my fuel door and some fuel vapor smells on Red Cone I’ve (thankfully) never had any CEL lights. Did Imogene Pass today and no issues at all. I have a hunch lower octane fuel suffers from this more than higher octane though I don’t think it’s immune. But it’s just a theory at this point

I remember some discussion in this section on the vapor pressures of different octanes a while back and my takeaway was there may be some benefit, but it is highly location and even batch specific. Even ethanol.. I tend to run ethanol free once I get to Durango and that’s what I boiled a couple years ago, in cooler weather than was typical, as I remember it.

But yes whatever fuel doesn’t as readily expand rotopax should be better about preventing this.

 

[kcjaz]

Interesting discussion fuel cooling here. Does anyone know how hot the return fuel gets? Gasoline can start to boil at 95F depending on blend (there is winter and summer gas partially for this reason) but there isn't a single boiling point as it is a blend of things that have different boiling points. I think I've seen numbers from 95F to 400 F as the range for gasoline boiling point. A cooler makes sense and they are out there and you can buy them both air and water cooled. Water cooled would only do something if the hot fuel was >200F going in and 200 F is a lot more that 95F. I suspect that you don't need to cool it below 95F to help the boiling issue. It would be good to know some return line temps and corresponding tank temps.

Also, anyone have fuel pump specs? I would think the pump would have to be capable of 15 gal/h (I see 5ish gal/h on OBDII cruising down the highway with spikes >10 when I put my foot in it. The Pump has to accommodate WOT). My point here is that there is that the return flow is likely pretty high when idling or moving slowly. 90 minutes of idle could recirc your 24 gallon tank at idle. If the return is coming back at 200 F I could see that being a big part of this.

At LCDC on Red Cone, I had minor boiling. It was the first time I have ever noticed it on my truck. You could see a good number of the trucks were giving off vapors. Another 200 had what I would call major boiling. You could hear it and gas was literally raining from his gas flap. If it is just the simple physics of heat build up, when is there such a variation on the same trail? (oh, I tend to just let my truck run all the time on the trail. Not sure about the other guy).

 

[TheGrrrrr]

One thing that seems to be forgotten in the latter stages of this thread is what @Taco2Cruiser found about the engine design using returning fuel to cool parts of the top end. We can try to mitigate heat transfer all over the place, but if the return fuel is actually being used as part of the engine cooling strategy, then none of that mitigation will help. The only solution would be to take the heat soaked from the engine cooling out of the return fuel with a cooler of some sort. Heat shields, fuel line wraps and the like would do nothing if that fuel is being heated intentionally to help cool engine components before it hits the return lines.

I would love to see an aftermarket fuel cooler for the return fuel as it sounds like this is the only thing that would make a consistent difference. I know nothing of how the engine or fuel system work but I do know that much of what is being discussed recently in this thread has already been discussed at length earlier in the thread. It seems like we are talking in circles. What would be helpful is if someone with knowledge of the engine and fuel system could confirm or validate @taco2cruisers findings and establish that as baseline knowledge, which would let us focus on how to cool the return fuel instead of continuing to focus on how to keep heat away from the return fuel.

 

[bloc]

Also, anyone have fuel pump specs? I would think the pump would have to be capable of 15 gal/h (I see 5ish gal/h on OBDII cruising down the highway with spikes >10 when I put my foot in it. The Pump has to accommodate WOT). My point here is that there is that the return flow is likely pretty high when idling or moving slowly. 90 minutes of idle could recirc your 24 gallon tank at idle. If the return is coming back at 200 F I could see that being a big part of this.

Our trucks step down fuel pump voltage at lower flows.. but that means the fuel in the rails has more time to sit there and heat up. Ultimately it is probably a similar amount of thermal energy being carried back to the tank.

 

[nwfl4runner]

One thing that seems to be forgotten in the latter stages of this thread is what @Taco2Cruiser found about the engine design using returning fuel to cool parts of the top end. We can try to mitigate heat transfer all over the place, but if the return fuel is actually being used as part of the engine cooling strategy, then none of that mitigation will help. The only solution would be to take the heat soaked from the engine cooling out of the return fuel with a cooler of some sort. Heat shields, fuel line wraps and the like would do nothing if that fuel is being heated intentionally to help cool engine components before it hits the return lines.

I would love to see an aftermarket fuel cooler for the return fuel as it sounds like this is the only thing that would make a consistent difference. I know nothing of how the engine or fuel system work but I do know that much of what is being discussed recently in this thread has already been discussed at length earlier in the thread. It seems like we are talking in circles. What would be helpful is if someone with knowledge of the engine and fuel system could confirm or validate @taco2cruisers findings and establish that as baseline knowledge, which would let us focus on how to cool the return fuel instead of continuing to focus on how to keep heat away from the return fuel.

I've got a Setrab FP119M22I and oem fuel lines sitting in my garage right now as I try to figure out best way to route from the quick disconnect right above the tank to the cooler. Advantage to being on 37s is my whole spare tire location is wide open, so I'm going to mount it there and reroute it back into the tank.

 

[TheGrrrrr]

I've got a Setrab FP119M22I and oem fuel lines sitting in my garage right now as I try to figure out best way to route from the quick disconnect right above the tank to the cooler. Advantage to being on 37s is my whole spare tire location is wide open, so I'm going to mount it there and reroute it back into the tank.

That will definitely be worth a thorough write-up regardless of the outcome. I look forward to seeing what you come up with. I would love to do something similar to contribute to the tech of this, I just don't have the prerequisite knowledge or skill to do so safely. I also don't have a good space to do the work. I can, however apply some skill and knowledge to the logistics of replicating a good design and making it available.

 

[kcjaz]

Has anyone with an aux tank tried filling the main tank when the main tank is boiling? That should cool it down and maybe stop the boiling??? Of course that isn't a solution but just a way to test the theory.

I've got a Setrab FP119M22I and oem fuel lines sitting in my garage right now as I try to figure out best way to route from the quick disconnect right above the tank to the cooler. Advantage to being on 37s is my whole spare tire location is wide open, so I'm going to mount it there and reroute it back into the tank.

I assume you are talking about a air cooled cooler under the truck in the spare tire location. While just having heat rejection surface area (the HX itself) has to help, I would think air flow is needed. The issue seems to be low speed or idle so I wonder how effective air cooled HSs would be. I suppose an electric fan could also be part of this.

@TheGrrrrr, maybe you could just run the return fuel line through your shower heater on your roof rack and get both cool fuel and hot water...

 

[nwfl4runner]

Has anyone with an aux tank tried filling the main tank when the main tank is boiling? That should cool it down and maybe stop the boiling??? Of course that isn't a solution but just a way to test the theory.

I assume you are talking about a air cooled cooler under the truck in the spare tire location. While just having heat rejection surface area (the HX itself) has to help, I would think air flow is needed. The issue seems to be low speed or idle so I wonder how effective air cooled HSs would be. I suppose an electric fan could also be part of this.

@TheGrrrrr, maybe you could just run the return fuel line through your shower heater on your roof rack and get both cool fuel and hot water...

No mine has the fan attached as well. Gonna be power baby!