Gas tank building excessive pressure & fuel smell. Dangerous for sure! Why does this happen?

[Skidoo]

Here is what a new Toyota radiator for a 2000LC looks like

 

[kbfj621989]

Oh that makes sense now, thanks! Will see about dropping a new filter in there.

As for the foam, do you have any pics that could guide me as to how I could apply it?

Unless it’s due for a change, you should be able to massage the gasket back into place. I added some RTV to the channel where the gasket meets the filter frame (no RTV to the filter box) to hold it in place.

 

[2001LC]

@2001LC , I appreciate you taking the time to respond. I'm going to respond to some of the points just as a matter of setting the record straight, as I think the pictures may be misleading you.

Not trying to be argumentative, but I will say I don't think trying to ascertain "wrencher experience" advances the objective, or serves any purpose.



On a flat surface, the brake fluid is a hair or two over the full line. In this photo it's not on a flat surface... rather pointing downhill pretty good, so likely looks worse to you than it really is. Don't know what you mean by dark.

Brake Fluid Level, is set after pump brake pedal 40 times with IG key off.
Dark brake fluid indicates old and high moisture content. It may also indicate, mixing fluid.

Brakes ...... Overdue write-up.

First and foremost: Brakes should only be worked by those, with high level of mechanical abilities and experienced with brake systems. With the age of all 100 series today, in our aging fleet. Any issue, with brake master assembly. IMHO, best and safest course of action. Have the whole brake...

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1. It doesn't run hot. This past trip is the only time I've ever seen coolant temp hit 200. Usually is in the 185-190 range.

I was responding to this (below) earlier post by you, hitting 205f and gas cap venting.

****

As I got closer to Denver around 1pm local time, temps were averaging ~203. I saw 205 a couple brief moments. Definitely the hottest I've ever seen it. Don't think I've ever seen it hit 200 before.

It was hot out, no doubt. Phone said low 90s. Dashboard board said 95.

When I finally got to my destination and got out of the LX, I could smell gas while out in the driveway. Opened the gas cap to vent it and there was a LOT more than the normal hiss. Pressure was really high. It took probably a half hour (at least) before I wasn't smelling gas while standing in the driveway any longer.

The silver lining is it never smelled inside the cabin while driving, and no gas boiled out in my new-to-me driveway.

Do 200s have this problem?

2. A couple days before the trip, I actually used your "how to" thread to clean the fins. So they might not be fresh-out-the-box clean, but they should be relatively clean.

Good. The more we clean the better. But if not clean for years/miles and years/miles. They'll not clean well.

It's full of Toyota red.

Good looked empty. BTW: You did mean 50/50 red/D-water.

I agree it's aftermarket and there's no OEM foam. However, lots of people running Denso radiators sans OEM foam.

Lots of people run hot.

Maybe I'm not seeing what you're seeing... but it looks pretty normal & clean to me. I believe the filter was replaced at last oil change just a few thousand miles ago.

Curled filter seal.

I'm due for another oil change when I get back to Omaha. I'll ask my shop to see whether they think the CC worth doing it now or if they think some of these and/or other things should be looked at first.

I thought, you're wrenching your rig.. Most shops' especially INDY, don't have a clue. I work on 100 series, 7 days a week and have for many years and a few 200 series. Nothing else!

Most of what I do, is correcting what other shops have touch. That and the damage their improper service results in.

Best correct all first, before install a CC.

 

[nikoli]

Brake Fluid Level, is set after pump brake pedal 40 times with IG key off.
Dark brake fluid indicates old and high moisture content. It may also indicate, mixing fluid.

Brakes ...... Overdue write-up.

First and foremost: Brakes should only be worked by those, with high level of mechanical abilities and experienced with brake systems. With the age of all 100 series today, in our aging fleet. Any issue, with brake master assembly. IMHO, best and safest course of action. Have the whole brake...

forum.ih8mud.com

I was responding to this (below) earlier post by you, hitting 205f and gas cap venting.




Good. The more we clean the better. But if not clean for years/miles and years/miles. They'll not clean well.

Good looked empty. BTW: You did mean 50/50 red/D-water.

Lots of people run hot.

Curled filter seal.

I thought, you're wrenching your rig.. Most shops' especially INDY, don't have a clue. I work on 100 series, 7 days a week and have for many years and a few 200 series. Nothing else!

Most of what I do, is correcting what other shops have touch. That and the damage their improper service results in.

Best correct all first, before install a CC.

I wrench on things when time allows... which is exceedingly rare these days as we are busy trying to move from Omaha to Arvada. So the LX goes to Toyo Techs here in Omaha for big deal items or when I just don't have the time... thus, they're doing the oil change and fixing the air filter. I'll apply foam to the radiator when I get it back.

It has been a while since I've read through this thread, and I do not recall whether any progress was made in determining what is normal / expected given certain conditions and scenarios. It may be useful to establish when one could reasonably expect to experience the symptoms described in this thread (excessive pressure & fuel smell, boiling, etc).

For instance, under normal operating conditions this LX runs between 185-190 degrees... which if I'm not mistaken is a healthy / normal coolant temp. "Normal operating conditions" in this case would include a mostly stock 100 series, sub 90 degree OAT, normal driving observing speed limits, not towing anything or rock crawling.

However, when I added a ~3k pound trailer the coolant temp range bumped up about 3-4 degrees to 188-194. Is it reasonable to expect that kind of increase given the trailer and all it entails? (Driving ~60mph with the tranny in "4").

Then as the day wore on and OAT went from low 80s to mid 90s, coolant range began bouncing between 198-203. Is it reasonable to expect that kind of increase? At that point, should we expect to experience the symptoms described in this thread?

 

[2001LC]

I wrench on things when time allows... which is exceedingly rare these days as we are busy trying to move from Omaha to Arvada. So the LX goes to Toyo Techs here in Omaha for big deal items or when I just don't have the time... thus, they're doing the oil change and fixing the air filter. I'll apply foam to the radiator when I get it back.

It has been a while since I've read through this thread, and I do not recall whether any progress was made in determining what is normal / expected given certain conditions and scenarios. It may be useful to establish when one could reasonably expect to experience the symptoms described in this thread (excessive pressure & fuel smell, boiling, etc).

For instance, under normal operating conditions this LX runs between 185-190 degrees... which if I'm not mistaken is a healthy / normal coolant temp. "Normal operating conditions" in this case would include a mostly stock 100 series, sub 90 degree OAT, normal driving observing speed limits, not towing anything or rock crawling.

However, when I added a ~3k pound trailer the coolant temp range bumped up about 3-4 degrees to 188-194. Is it reasonable to expect that kind of increase given the trailer and all it entails? (Driving ~60mph with the tranny in "4").

Then as the day wore on and OAT went from low 80s to mid 90s, coolant range began bouncing between 198-203. Is it reasonable to expect that kind of increase? At that point, should we expect to experience the symptoms described in this thread?

Those ECT seems fine. Much better than you stated earlier, at lower OAT and with higher ECT.

Contact me we you get to Arvada, if you'd like to stop by. I can look over your 05, and see what I can find in a lite inspection. I also have some radiator side foam on their bracket.

 

[Postman454]

Thanks all for the info and data on this issue. I have had this issue three times since purchasing our 2006 LX470 4 years ago (130K - 160K).

1st time was camping trip Denver to Ouray(August 2023), towing small camping trailer less than 1500lb, truck fully loaded, had gas cap vapor, small amount of gas at cap when stopping on an offroad trail to find a camp site, in 4lo, elevation 8,000', outdoor temp mid 90s, truck also stalled but started back up, 87 octane (10% ethanol). no other issues during this trip, did Imogene pass

2nd time was trip from Moab trip back to Denver(June 2025), no trailer, not heavily loaded, filled up with 87 octane (10% ethanol) in Fruita, stopped in Edwards for rest stop, over 7,000' elevation, outdoor temp in mid/high 90s, ECT 190 deg F and below. Engine would not start back up, had to wait 20 min for it to cool, some vapor from gas cap but not bad.

3rd time was camping trip from Denver to Tin Cup Pass(June 2025), towing small camping trailer, fully loaded down, had gas cap vapor, small amount of gas at cap when stopping on an offroad trail to find a camp site, was in 4lo for a mile, elevation 10,000', outdoor temp 99 F in Denver, 80 F in Salida, ECT 185-195 deg F most of trip, got up to 202 F over one pass, was 185 F when in 4lo. gas tank between 1/2 & 1/4 full with 87 octane (10% ethanol). Fuel trims during trip were under 8%.

I keep the truck up to date on maintenance, use OEM parts, clean original radiators every 5K or as needed, clean MAF and throttle body yearly, new air filter, new muffler, original catalytic converters, no exhaust leaks, replaced coolant and transmission fluid in 2023 with timing belt, newer thermostat, minimal rust, do not top off tank

Between the 2nd and 3rd time this happened I replace the gas cap with new OEM, added a aluminum catalytic shield by the fuel lines and wrapped the lines in the Velcro insulation. I intend to use the metal insulation wrap on the sides of the tank. Also have a fuel pump, fuel filter and spark plugs on order.

Each time it has happened it is at elevation of 7,000 or more and after 3+ hours of driving, ECT mostly with in range

Has anyone tracked catalytic converter temperatures from the 02 sensors? what is a normal operating range? I recorded temperatures above 1400 deg F on our most recent trip from Denver to Tin Cup going over some of the passes with the trailer. Normally they are under 1000 deg F. I suspect I am running rich or lean causing the catalytic converters to run hotter than normal and thus causing all the extra heat to soak the tank, heat the fuel and cause my issues. Other than spark plugs what else can I do to resolve this?

 

[2001LC]

Thanks all for the info and data on this issue. I have had this issue three times since purchasing our 2006 LX470 4 years ago (130K - 160K).

1st time was camping trip Denver to Ouray(August 2023), towing small camping trailer less than 1500lb, truck fully loaded, had gas cap vapor, small amount of gas at cap when stopping on an offroad trail to find a camp site, in 4lo, elevation 8,000', outdoor temp mid 90s, truck also stalled but started back up, 87 octane (10% ethanol). no other issues during this trip, did Imogene pass

2nd time was trip from Moab trip back to Denver(June 2025), no trailer, not heavily loaded, filled up with 87 octane (10% ethanol) in Fruita, stopped in Edwards for rest stop, over 7,000' elevation, outdoor temp in mid/high 90s, ECT 190 deg F and below. Engine would not start back up, had to wait 20 min for it to cool, some vapor from gas cap but not bad.

3rd time was camping trip from Denver to Tin Cup Pass(June 2025), towing small camping trailer, fully loaded down, had gas cap vapor, small amount of gas at cap when stopping on an offroad trail to find a camp site, was in 4lo for a mile, elevation 10,000', outdoor temp 99 F in Denver, 80 F in Salida, ECT 185-195 deg F most of trip, got up to 202 F over one pass, was 185 F when in 4lo. gas tank between 1/2 & 1/4 full with 87 octane (10% ethanol). Fuel trims during trip were under 8%.

I keep the truck up to date on maintenance, use OEM parts, clean original radiators every 5K or as needed, clean MAF and throttle body yearly, new air filter, new muffler, original catalytic converters, no exhaust leaks, replaced coolant and transmission fluid in 2023 with timing belt, newer thermostat, minimal rust, do not top off tank

Between the 2nd and 3rd time this happened I replace the gas cap with new OEM, added a aluminum catalytic shield by the fuel lines and wrapped the lines in the Velcro insulation. I intend to use the metal insulation wrap on the sides of the tank. Also have a fuel pump, fuel filter and spark plugs on order.

Each time it has happened it is at elevation of 7,000 or more and after 3+ hours of driving, ECT mostly with in range

Has anyone tracked catalytic converter temperatures from the 02 sensors? what is a normal operating range? I recorded temperatures above 1400 deg F on our most recent trip from Denver to Tin Cup going over some of the passes with the trailer. Normally they are under 1000 deg F. I suspect I am running rich or lean causing the catalytic converters to run hotter than normal and thus causing all the extra heat to soak the tank, heat the fuel and cause my issues. Other than spark plugs what else can I do to resolve this?

Sound to me like you've two issues:

1a) Sign of bad fuel pump, in the 06-07. Stalls after high RPM (~3K or more) prolonged for a few minutes, more so on a high OAT sunny day. Heat generated by 12 Volt current and pump itself, along with high OAT. Results in high resistance in wiring and pump motor. As we let off the gas pedal, current to fuel pump, drops as it should to reduce speed of pump. But do to, increased resistance. Fuel doesn't get enough current (AMPs). Fuel pump speed drops, to low to deliver adequate fuel flow/pressure to fuel rail. Often times. If we scan for DTCs (codes), before IG key turned off. We'll see BK1 & BK2 lean codes pending.

1b) Weak fuel pump. LTFT should run around 1 to 3% in high altitude (miles high city). While steadily cruising on HWY (RPMS & MPH steady, no hills). LTFT 8%, is lean fuel air mixture. STFT should be ~0% -+2. Lean mixture, cylinder head temp goes up. Assuming no vacuum leaks. When I see FT running "lean". I very often find iron rust in gas tank. Which damage fuel pump and clogs sock & fuel filter. This is from old gas station. That still have iron storage tanks.

2) Charcoal canister, contamination, in happens all to often in 03-up.
Once fuel gets as high as cap, CC is flooded. It just gets worse from there. Overfilling (adding gas after auto shut off, of fueling pump handle), filling on hot day then parking on hot pavement, not driving to draw down gas before climbing hill with full tank, bell-pans create heat tunnel, etc.. All and more, can result in flood CC. They just get worst from there.

250K miles 2006 LX470

Additionally some have very gunk fuel filters.

24K miles 2007 LC. Gas cap and fill area nasty, 24K miles. CC was second heaviest (contaminated) I've seen. It came from sea-level near gulf coast (flat lands):

Fill neck

Inner vent port near underside of cap

 

[Postman454]

Sound to me like you've two issues:

1a) Sign of bad fuel pump, in the 06-07. Stalls after high RPM (~3K or more) prolonged for a few minutes, more so on a high OAT sunny day. Heat generated by 12 Volt current and pump itself, along with high OAT. Results in high resistance in wiring and pump motor. As we let off the gas pedal, current to fuel pump, drops as it should to reduce speed of pump. But do to, increased resistance. Fuel doesn't get enough current (AMPs). Fuel pump speed drops, to low to deliver adequate fuel flow/pressure to fuel rail. Often times. If we scan for DTCs (codes), before IG key turned off. We'll see BK1 & BK2 lean codes pending.

1b) Weak fuel pump. LTFT should run around 1 to 3% in high altitude (miles high city). While steadily cruising on HWY (RPMS & MPH steady, no hills). LTFT 8%, is lean fuel air mixture. STFT should be ~0% -+2. Lean mixture, cylinder head temp goes up. Assuming no vacuum leaks. When I see FT running "lean". I very often find iron rust in gas tank. Which damage fuel pump and clogs sock & fuel filter. This is from old gas station. That still have iron storage tanks.

2) Charcoal canister, contamination, in happens all to often in 03-up.
Once fuel gets as high as cap, CC is flooded. It just gets worse from there. Overfilling (adding gas after auto shut off, of fueling pump handle), filling on hot day then parking on hot pavement, not driving to draw down gas before climbing hill with full tank, bell-pans create heat tunnel, etc.. All and more, can result in flood CC. They just get worst from there.

250K miles 2006 LX470
View attachment 3945822View attachment 3945821
View attachment 3945824View attachment 3945825
Additionally some have very gunk fuel filters.
View attachment 3945827

24K miles 2007 LC. Gas cap and fill area nasty, 24K miles. CC was second heaviest (contaminated) I've seen. It came from sea-level near gulf coast (flat lands):
View attachment 3945848
Fill neck
View attachment 3945854
Inner vent port near underside of cap
View attachment 3945856

View attachment 3945852
View attachment 3945850

Thanks Paul, I will look into those items when new fuel pump gets here this week. Any thoughts on catalytic temperatures?

 

[2001LC]

Thanks Paul, I will look into those items when new fuel pump gets here this week.

Any thoughts on catalytic temperatures?

Not sure what you're asking?

 

[Postman454]

Not sure what you're asking?

Wondering if the catalyst temperatures can tell us anything. I did a test run last night, Denver elevation, 75 deg f outside temp, let truck warm up, 185 F coolant temp, then highway speed, no trailer, light load and got the below values. Looks like my fuel trims are high. The catalyst temperature was in the 1400 deg F. When in the mountains with trailer fully loaded down, going up a pass the catalyst temperatures were in the 1600-1700 deg F.

 

[2001LC]

Wondering if the catalyst temperatures can tell us anything. I did a test run last night, Denver elevation, 75 deg f outside temp, let truck warm up, 185 F coolant temp, then highway speed, no trailer, light load and got the below values. Looks like my fuel trims are high. The catalyst temperature was in the 1400 deg F. When in the mountains with trailer fully loaded down, going up a pass the catalyst temperatures were in the 1600-1700 deg F.

View attachment 3947001View attachment 3947002View attachment 3946996View attachment 3946997

CAT temps sound good, as do FT.

I can't get a good read on FT or CAT temps, as I don't know your RPM & MPH or if holding steady!

CAT temps cruise on HWY run ~ 1,200-1,400F. When engine loaded or say I'm running on HWY at 4,500 -5,500 RPM, I max ~1,650F. I've never tried pulling a load up a mtn pass. But I would expect CAT temp to go higher.

I watch RPM, MPH and ECT. When looking a data stream logs. MPH & RPM, tell me if I'm cruising steady on high, in D and flat ground, no change whatsoever in throttle position. It's that steady load on engine, that gives the most useful FT data. I like to see (in the miles high city) LTFT~ 0-3% and STFT ~0% +-1.5. When I see LTFT around 7%, I find vacuum leaks or weak fuel follow.

Keep in mind: LTFT is what ECU is doing, working to achieve STFT of 0%. So a LTFT of say 7%, is a lean (more air than fuel in mixture) running engine. Cylinder head temps, run hot, when running lean. So, CATs will also. Where as cylinder head temps run cool, when running rich (more fuel than air in mixture). To much fuel in mixture can load up CAT with fuel, which can ignite and burn up CATs. Burnt up CAT, is most often associated with a bad MAF sensor.

When running lean: I first make sure no vacuum leak. Second add 2x cans 44K to gas. If still running lean after running through full tank of gas & 44K. I'm finding, replace fuel pump and fuel filters, brings fuel trims in line

Another thing to watch with ECT, is ATF temp. Transmission fluid running ho, heat is shed off the first radiator (ATF oil cooler) onto the next two radiators (AC condensor & engine).

Exhaust pipes (CAT & piping), shed heat:
If you've a pure stock rigs undershield, I'd not bother shielding.
If armor covering all the way to transmission. Consider shielding.
If full armor, with bell pan. Shield and air diverts, may serve you well.

Those big heavy iron bumpers and winch, also retain heat and shed onto radiators. More air flow holds, the better.

Radiator fins need cleaning! Alert Alert Alert

I've a 06LC w/192K I just bought. In reading history I found PO complained of engine temp raising when both front and rear AC on. Toyota Dealership diagnosed with clogged radiator fins. Recommended new OEM radiator, $600 for the US spec Radaitor plus coolant and labor. They should have added...

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