Engine overheat (1FZ-FE) (3 Viewers)

[OrangeCrusher]

My rig is overheating when going up a circa 6% grade at full power. It's on I-80 East in Utah going up Parleys Summit, for those familiar. It's a busy stretch of Interstate where normal traffic goes 70mph, except for some heavy semis.
I'm driving it in 2nd gear and it is barely able to keep about 65mph - I assume this is normal. The rig is rather light for an 80 series, probably around 5,300lb. No engine tuning like turbos or custom cams that I'm aware of.

Today's air temperature was about 60F (15C). I was monitoring the ECT temperature via bluetooth app / OBD1 port. It was reading super high, 250F / 120C and higher. It's been doing this for a while and I couldn't quite believe it's actually this high so I carried an IR heat sensing camera to compare. That measured somewhat lower - circa 10C lower, but still very high. I was driving it up and down stopping multiple times to check what the actual temperature is and if anything is boiling over. Eventually I pushed it very far - hopefully not too far - and there were maybe a few ounces of coolant boiling out of the overflow outlet when I stopped. The measured temperature with the IR camera of the top of the radiator was 117C / 242F at that point.

Here link to video taking a few seconds later, showing coolant rinsing out the overflow:


First question - this cannot be normal? It must be possible to go up this interstate while flowing with traffic? Or is the stock cooling system so weak that this is not possible by design?

Then assuming this is not normal - appreciate ideas of what the root cause could be. I've tested / improved most of the typical candidates already so I'm feeling stuck now.

According to FSM, this is the order of things to check for "Engine overheat":

1. Coolant leakage
   
   1. Not the case - it's not losing coolant. The level in the overflow bottle stays constant over months and the level is somehwere between low and high. There is also no air in the radiator, or in the heater core, or anywhere else I can test.
2. Cooling fan system
   1. I suspected the fan clutch may be defect and replaced it with a new Aising blue hub one earlier this week. It didn't really change anything so I assume there was nothing wrong with the old one. The fan itself has a few scratches but is not obviously broken and certainly moving air.
3. Radiator and radiator cap
   1. Radiator looks in acceptable shape and is not obviously broken. I also flushed the entire system a few months ago to get out as much gunk as I can. Looking at it with the IR camera, there are no obvious cold spots that would indicate blockages. There are a few insects here and there stuck on the outside, but nothing crazy and certainly air is moving through.
   2. Radiator cap has been replaced with new OE cap a few months ago (old one was leaking).
4. Thermostat
   1. Has been replaced half a year ago with a new OE one. I cannot completely rule out that e.g. it is not fully opening, but it is certainly directing coolant through the radiator. This is evidenced by the radiator being hot throughout.
5. Timing chain
   1. Now this is an interesting one - I didn't even think of this. I don't know much what is going on with the timing chain. I did a valve clearance check about half a year ago and didn't notice anything wrong but also didn't pay a lot of attention to it. Is this a likely cause of overheating?! Wouldn't there also be other symptoms - like poor power - if the timing was completely off?
   2. I have checked ignition timing a few months ago, and set it to the typical recommended value of about 5-7 degrees advanced.
6. Water pump
   1. Again nothing obviously wrong - e.g. cabin heat is working well, coolant is clearly circulating. I inspected it from the outside when I replaced the fan clutch. Spins freely, bearing play is on the high side but seemed acceptable.
7. Valve timing
   1. Similar to timing chain - I don't know if it's off as I haven't checked. I don't think it is likely as the engine is otherwise running OK. Is this a likely cause for overheating?
8. Spark plug
   1. Spark plugs themselves are in great condition, just pulled one out a few days ago.
   2. However there is an issue with the distributor - oil is leaking into it and seems to be gunking up the rotor / cap contacts. I just cleaned it a few days ago, however it's still not good, at idle the engine stumbles at times. I've ordered all the parts to rework the distributor but it will be another week until they have all arrived.
      1. There are no misfires however at power. So I struggle to see how this could lead to overheating issues.
9. Knock sensor circuit
   1. both knock sensors were bad when I bought the truck a year ago, and I have replaced both with OE. I haven't checked recently if there are still any knock sensor codes - something I will do tomorrow.
10. Oil pump?!
11. Cylinder head ?!
12. Cylinder block ?!
13. ECT Sender gauge
    1. It appears to be reading about 10degrees too high, but even considering that the actual coolant temperature still seems way too high. I'm ordering a new sensor now but can't see how this is causing the symptoms

Going through the above list, next I could go check the valve timing, as well as fix the distributor. I will fix the distributor anyway but am not convinced the valve timing is causing this. I also think the things down the list like oil pump, cylinder head, cylinder block would all cause some other more obvious symptoms? E.g. it does not have excessive blowby, no cylinder head / gasket symptoms.

Any input / thoughts / challenges are well appreciated!

 

[Kernal]

"I'm driving it in 2nd gear"

Is that at 70mph?
What rpm is your engine turning at that speed (stock gearing, tire size)?
For how long/miles do you push it in 2nd?

 

[robnicko]

is there any obstruction to the front of the radiator, bugs, dirt, leaves etc restricting airflow?

have you felt the bottom radiator hose compared to the top, the bottom should be considerably cooler than the top and if not the radiator could be clogged up?

are your drive belts ok & not slipping

 

[AussieHJCruza]

Check that your fan clutch is actually engaging properly, have seen some new ones with low fluid and a lot of variance in how they're set to open out of the box

 

[CruiserDave]

Like said above check fan clutch and I would retard the timing. 5-6 degrees seems a bit much.

 

[bkfj40]

I stopped reading at the statement of in second gear at 65 mph. What rpms you turning at that speed there @OrangeCrusher ?

 

[voodu3]

I had a similar issue with my 93 pulling long hills. I replaced every part in the cooling system but the cure was a new radiator. I did this last because it had been done just before I bought it. I got one of the TYC from Amazon and I haven’t had a cooling issue since. I never got to 250* but it would hit 240* before. I highest I’ve had after was 205* on a 100* day in Atlanta traffic. I run the same timing advance. I hope this helps.

 

[Sacred80]

Reminds me of when I had a “stuck open” thermostat a few years ago that would seem fine in most instances but then would overheat. After a pause it would seem to be fine again. I got a new one from the dealer and fresh new red coolant and that cured my problem.

Other than that suggestion , going 65 in second gear sounds like you were in a mid ‘90s Supra instead of an LC.

 

[OrangeCrusher]

"I'm driving it in 2nd gear"

Is that at 70mph?
What rpm is your engine turning at that speed (stock gearing, tire size)?
For how long/miles do you push it in 2nd?

Engine is at circa 4,500rpm. It's on 37s with stock gearing. @bkfj40

I certainly don't like going up there in 2nd gear and with this high rpm, but it's the only option if you don't want to crawl it up at 35mph while being passed by a semi. This is at 7,000ft / 2,000m, so atmospheric pressure is 20% lower than sea level. Hence engine power will also be reduced accordingly.

is there any obstruction to the front of the radiator, bugs, dirt, leaves etc restricting airflow?

have you felt the bottom radiator hose compared to the top, the bottom should be considerably cooler than the top and if not the radiator could be clogged up?

are your drive belts ok & not slipping

There is the AC condenser and the (smaller) transmission fluid cooler in front of the radiator as I think is stock. The front of both is rather clean with a minimal number of dead insects stuck in it. I can clean it but doubt this is the issue at it is way cleaner than the average car is in my experience.
I did notice that all three (radiator, AC condenser, transmission oil cooler) are black painted, rather than bare aluminium metal as is common otherwise. I assume this stock, or could this be a flawed DIY paint job? The radiator itself seems to be made not of aluminium but probably copper / bronze or something like that.

Bottom of radiator hose I pointed the IR camera to it a few minutes later when the engine had cooled down a bit. It was something like 70-80C (170F). So about 20C cooler than the inlet. That's cooler but not massively cooler - I don't know if it's normal? This would still be very hot to the touch.

Drive belts have been replaced together with the fan clutch and are not currently slipping.

@AussieHJCruza how do you recommend I check the fan clutch?

@Sacred80 I might swap the thermostat just in case, thanks!

 

[1MAC]

1. I'd probably swap in a new radiator. It's not difficult or expensive and it sounds like you don't know how old yours is.
2. Bring the timing down to factory spec.
3. Are you sure you're getting data via OBD1? If it's OBD2 and you're using an app, do you have any codes? A lean condition will make a lot of heat. What are your short and long term fuel trims?

 

[jpoole]

Tune your fan clutch. I have personally seen new blue hubs that were insufficient out of the box and have read of others seeing the same and I wouldn't run one that hasn't been tuned. You can piece together how to tune the fan clutch here:

Blue fan clutch mod...Thread has gone to hell, read at your own risk

History: On my first drive this summer after replacing my transmission I was having an overheat condition with the truck. On the following weekend while towing a camper it was real severe in the 230* range. After returning I was able to confirm that my Blue hubbed fan clutch was to blame...

forum.ih8mud.com

​

Note that the above thread is old and starts out with discussion of much lighter oils that folks are running these days. There have many been solid posts about fan clutch tuning over the years so searching will yield more info but it isn't that complicated and you should just knock it out and monitor your before/after temps and temps in different conditions so that you can make further adjustments as needed. I did a number of tests and made small adjustments over a few years and this is the setup I'm currently running which does well in the SouthEast including towing a 3k lb camper to the nearby mountains and on the highways pretty regularly:

50% open at 100, 20kcst to top of oval holes​

​

One counter intuitive point is non-fan driven airflow drops off on 80s as speeds climb towards and above 60mph. It's been years since I did that testing but at one point when I had a weakly tuned fan clutch I was able to clearly hit higher speeds where air flow dropped off and temps started to climb quickly. Point being that the fan is crucial for operating at lower and higher driving speeds while natural air flow will help keep the rad cooler through moderate speeds (20 to 50 roughly).

Foam between the radiator and core support will also help ensure that you are pulling cool air through the radiator and not recirculating hotter air from the engine bay through the radiator. Cleaning the condenser and radiator annually, or more often, is also good practice and I typically spray them in a mild acid like simple green then flush them after it's soaked for a while followed by straightening condenser fins / clearing blockages.

You may have other issues as mentioned above but you need to know that the fan clutch is setup correctly before going much further in your efforts in my opinion.

​

 

[bkfj40]

I feel for ya up at 7k feet. We nicknamed our 80 "nebraska" as it was happiest in Nebraska on our drive from Virginia to Idaho. When we do teton pass into wyoming all the time, the 80 just doesn't have the oomph and that is with stock tires. 37s and stock gearing isn't helping ya.

I'd try what others are mentioning - radiator and fan clutch.

 

[manofthewoods]

My rig is overheating when going up a circa 6% grade at full power. It's on I-80 East in Utah going up Parleys Summit, for those familiar. It's a busy stretch of Interstate where normal traffic goes 70mph, except for some heavy semis.
I'm driving it in 2nd gear and it is barely able to keep about 65mph - I assume this is normal. The rig is rather light for an 80 series, probably around 5,300lb. No engine tuning like turbos or custom cams that I'm aware of.

Today's air temperature was about 60F (15C). I was monitoring the ECT temperature via bluetooth app / OBD1 port. It was reading super high, 250F / 120C and higher. It's been doing this for a while and I couldn't quite believe it's actually this high so I carried an IR heat sensing camera to compare. That measured somewhat lower - circa 10C lower, but still very high. I was driving it up and down stopping multiple times to check what the actual temperature is and if anything is boiling over. Eventually I pushed it very far - hopefully not too far - and there were maybe a few ounces of coolant boiling out of the overflow outlet when I stopped. The measured temperature with the IR camera of the top of the radiator was 117C / 242F at that point.

View attachment 3902210

Here link to video taking a few seconds later, showing coolant rinsing out the overflow:


First question - this cannot be normal? It must be possible to go up this interstate while flowing with traffic? Or is the stock cooling system so weak that this is not possible by design?

Then assuming this is not normal - appreciate ideas of what the root cause could be. I've tested / improved most of the typical candidates already so I'm feeling stuck now.

According to FSM, this is the order of things to check for "Engine overheat":

1. Coolant leakage
   
   1. Not the case - it's not losing coolant. The level in the overflow bottle stays constant over months and the level is somehwere between low and high. There is also no air in the radiator, or in the heater core, or anywhere else I can test.
2. Cooling fan system
   1. I suspected the fan clutch may be defect and replaced it with a new Aising blue hub one earlier this week. It didn't really change anything so I assume there was nothing wrong with the old one. The fan itself has a few scratches but is not obviously broken and certainly moving air.
3. Radiator and radiator cap
   1. Radiator looks in acceptable shape and is not obviously broken. I also flushed the entire system a few months ago to get out as much gunk as I can. Looking at it with the IR camera, there are no obvious cold spots that would indicate blockages. There are a few insects here and there stuck on the outside, but nothing crazy and certainly air is moving through.
   2. Radiator cap has been replaced with new OE cap a few months ago (old one was leaking).
4. Thermostat
   1. Has been replaced half a year ago with a new OE one. I cannot completely rule out that e.g. it is not fully opening, but it is certainly directing coolant through the radiator. This is evidenced by the radiator being hot throughout.
5. Timing chain
   1. Now this is an interesting one - I didn't even think of this. I don't know much what is going on with the timing chain. I did a valve clearance check about half a year ago and didn't notice anything wrong but also didn't pay a lot of attention to it. Is this a likely cause of overheating?! Wouldn't there also be other symptoms - like poor power - if the timing was completely off?
   2. I have checked ignition timing a few months ago, and set it to the typical recommended value of about 5-7 degrees advanced.
6. Water pump
   1. Again nothing obviously wrong - e.g. cabin heat is working well, coolant is clearly circulating. I inspected it from the outside when I replaced the fan clutch. Spins freely, bearing play is on the high side but seemed acceptable.
7. Valve timing
   1. Similar to timing chain - I don't know if it's off as I haven't checked. I don't think it is likely as the engine is otherwise running OK. Is this a likely cause for overheating?
8. Spark plug
   1. Spark plugs themselves are in great condition, just pulled one out a few days ago.
   2. However there is an issue with the distributor - oil is leaking into it and seems to be gunking up the rotor / cap contacts. I just cleaned it a few days ago, however it's still not good, at idle the engine stumbles at times. I've ordered all the parts to rework the distributor but it will be another week until they have all arrived.
      1. There are no misfires however at power. So I struggle to see how this could lead to overheating issues.
9. Knock sensor circuit
   1. both knock sensors were bad when I bought the truck a year ago, and I have replaced both with OE. I haven't checked recently if there are still any knock sensor codes - something I will do tomorrow.
10. Oil pump?!
11. Cylinder head ?!
12. Cylinder block ?!
13. ECT Sender gauge
    1. It appears to be reading about 10degrees too high, but even considering that the actual coolant temperature still seems way too high. I'm ordering a new sensor now but can't see how this is causing the symptoms

Going through the above list, next I could go check the valve timing, as well as fix the distributor. I will fix the distributor anyway but am not convinced the valve timing is causing this. I also think the things down the list like oil pump, cylinder head, cylinder block would all cause some other more obvious symptoms? E.g. it does not have excessive blowby, no cylinder head / gasket symptoms.

Any input / thoughts / challenges are well appreciated!

My guess is that all (or most) of the ideas and suggestions in posts above contribute to the main cooling issues.

For me and my 1FZFE, I can't think of a moment that it's been at 4,500rpms.
I accept that I'll be passed by little old ladies, in Porches and Lamborghinis (never a Yugo, though, gotta draw the line)

 

[VSTL]

What I've gathered from the mud veterans, if the cooling system is satisfactory and it has adequate oil pressure, the 1FZ-FE is more than happy at 4K RPM.

 

[OrangeCrusher]

@manofthewoods I'm already letting it sit in on the trailer for all of the more distant places I'm going with it. The few miles I'm driving it I expect it to at least do a similar speed as it is going on the trailer This combo is going up also 65mph that same 6% grade.

 

[ChaseTruck]

Seems a bit early in the year for an overheating thread. Must be global warming, ahem, climate change…

I’d look at radiator and fan clutch. We’ve had good luck with the TYC radiator - on a ‘93 with S/C, 315’s, and stock axle gears, in the Phoenix, AZ heat. I have a blue fan clutch with 25k fluid in there right now (I had ~50k fluid in there, kept the truck cool, but seemed to steal a lot of power), we’ll see how it goes this summer with the 25k.

Not all radiators are created equal. I put a Koyo in the truck while it lived in Baton Rouge, and it worked well. About 5 years after that, the truck moved to AZ, and cooling was insufficient. That Koyo rad ‘looked’ fine, but the TYC, with a deeper core, made a clear difference, and worked better. Water pump overdrive pulley came later, and helped as well.

A lot of folks on this board swear by radiators from Mr. T. I’m just reporting what worked for that ‘93.

 

[OrangeCrusher]

@ChaseTruck can you share a link to the exact TYC radiator you are referencing? Thanks!

 

[SNLC]

What I've gathered from the mud veterans, if the cooling system is satisfactory and it has adequate oil pressure, the 1FZ-FE is more than happy at 4K RPM.

Yup 4k rpms is not a problem for the 1FZ. I have held mine at 4k for five to ten minutes climbing passes.

No problem.

Cheers

 

[Marco Lau]

Coolant dumping out of overflow around 235F, its the 1st sign of overheating and your engine attempt to shed excess heat. If you are maintaining 60-65 mph on 2nd, you should have enough air flow going into the radiator and at those RPM, your waterpump should be working hard to circulate the coolant from engine block to radiator. I would check the fan clutch. the clutch fan should lock up solid at those temp. Money on weak fan clutch.

I ran my 3F-E up 11000 ft up in Montana in second @ 4k + rpm fully loaded @ 6800 lbs going 25-35mph speed limit and the hottest i got was 210F with a 15k oil modded Aisen hub and a healthy cooling system and a large 2 core alum. radiator. I dont think 4k rpm will hurt the 1FZ-FE as it should rev. much better then the 3FE.

 

[OrangeCrusher]

3. Are you sure you're getting data via OBD1? If it's OBD2 and you're using an app, do you have any codes? A lean condition will make a lot of heat. What are your short and long term fuel trims?

This TOYOBD1 tool works great to read the key data out of the OBD1 port. It doesn't display codes though, I still need to read them by counting the flashes. I can do that later today.

Fuel trims - it doesn't show them and in either case they would be meaningless bc I had to replace the VAF with a custom built MAF unit. I can see that the O2 sensors are switched rich in that situation (4k rpm, full throttle). It is running in open loop then. I can also see the injection quantity (injector opening time), and comparing it to the closed loop full throttle values, it's running circa 10-20% rich, so something like lambda 0.8-0.9. Which should be ideal.