FJ62's Overheating. Several of us don't know why.

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Hey all,

I've been troubleshooting my FJ62 that runs quite hot when hitting hills and have tried everything I can think of to mitigate it.

Things I've done:

New Radiator (CSF)
New thermostat (OEM)
New Fan Clutch
New Water Pump (Had to replace anyway)
New AC Condenser (Old was clogged up and AC didn't blow very cold at all)
New Temp sender
Aftermarket gauge to confirm stock gauge readings
Checked the timing. Was originally off by 4 degrees but is now good.
Isolated tranny cooler (stacked plate Derale)
Heater works fine
System was burped
Radiator cap new
Vacuum lines replaced
Head gasket confirmed fine. (Compression is 150-155 across the board with 227k miles on it.

Basically, when driving the car and going up a steep grade if I'm on it for a like 30 seconds it the temps will creep to about 215. Doesn't matter what temp the outside is. Does the same thing in the middle of a Truckee winter. Some people I've spoken to have said that maybe it's normal but I drove my dad's FJ62 for YEARS and the temp always remained steady no matter what the temps were outside. I suppose that car is my baseline.

One thing I noticed today is that the Cold Start Injector sensor is cracked. Like the plastic is physically cracked that the connector fits to. I'm not sure if it's malfunctioning but considering I've tried pretty much everything I wanted to see if maybe that could be the culprit?

Another thing it COULD be is misadjusted valves. This is a new head and I only did the initial adjustment. That being said the valves are quiet in operation. I do plan on doing an adjustment in the next week.

Also, since it's been so hot in Truckee I was thinking of pulling the Tstat entirely and driving it to reno and back to see how high the temps get. I'd put the tstat back in after that. Would this be ill advised?

I'm grasping at straws and would appreciate any ideas, no matter how crazy they might seem.

Thanks!
 
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Oh, and I also have a Mishimoto aluminum radiator on the way since my new CSF has a pinhole leak and this is the SECOND one I've gotten through them. First was damaged in shipping so I guess I just don't trust them.
 
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Nothing with the cold start injector is going to cause an overheating problem. If the cold start injector were spraying all the time you'd likely feel power bogging,, have black smoke coming out the exhaust...and if anything slightly lower temps because rich mixtures are cooler than a lean condition.

How is your transmission cooler doing? you might put a before and after temp gage on it to get a feel for what sort of temps you are getting from the transmission
 
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Nothing with the cold start injector is going to cause an overheating problem. If the cold start injector were spraying all the time you'd likely feel power bogging,, have black smoke coming out the exhaust...and if anything slightly lower temps because rich mixtures are cooler than a lean condition.

How is your transmission cooler doing?

Tranmission cooler is just fine. It's now isolated from the main radiator and the temps are usually between 150-170F.
 
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OEM 88C (190F). I've replaced the tstat twice now.

You didnt put it in upside down by any chance? not sure that would cause an overheat issue...likely the opposite but just double checking


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These cooling systems are prone to air bubbles too. So even after burping the system it can take a while for all the air to come out.


Any difference in temp with high octane fuel?
 
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These cooling systems are prone to air bubbles too. So even after burping the system it can take a while for all the air to come out.


Any difference in temp with high octane fuel?
Also, it's been running for many many months without touching the cooling system. Truckee has a lot of hills too so it probably would've worked itself out by now.
 
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If a tank of high octane fuel solves the problem then its time to start investigating ignition, timing, carbon buildup on the valves, pinging etc.

Cool. Thanks for the suggestions! Another thing I didn't mention is that I use Rotella T4 diesel oil. That wouldn't do it, right?
 
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Cool. Thanks for the suggestions! Another thing I didn't mention is that I use Rotella T4 diesel oil. That wouldn't do it, right?

I doubt it. You are seeing higher temps when your engine load goes up...thats not abnormal as the engine is working harder. but if you think you are seeing abnormally high temps then you are either not getting adequate cooling or you are making heat faster than the stock cooling can get the heat out.
 
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Normally the first thing I would say is don't trust the stock temperature gage as they are notoriously inaccurate. but you mention having added an aftermarket gage as well and correlated similar readings.
 
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Whatever is happening is definitely abnormal. Last year I was slow climbing some fire trails and the thing would've boiled over had I not shut it off and let the motor cool off. I love this car but there is an asterisk every time I drive it that I'm just straight up tired of. I will eventually LS swap it but that's several years out.

Ron Diaz from CCFJ40 just told me not to pull the thermostat out. I've ordered a 180F 2F thermostat to try and see if the normal operating and max temps change. It won't go to waste in the end as my family has several 40's, one of which I'm rebuilding the motor and need a new thermostat anyway.
 

Dynosoar

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215 - 220F is not overheating for climbing under load for a few min. When temps get to 240-260 then there is a real problem. Does the temp "normalize" back to t-stat temp after the climb? It sounds like normal function to me.
Dyno
 
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215 - 220F is not overheating for climbing under load for a few min. When temps get to 240-260 then there is a real problem. Does the temp "normalize" back to t-stat temp after the climb? It sounds like normal function to me.
Dyno

The temps definitely hit 240 before. It was between the last white line and the red when I shut it off on the stock gauge. But yes, it does normalize eventually.
 
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I would double-check the temps by using an IR Temp gun on the head (engine off - IR guns DO NOT like air flowing past them from the engine fan). If your head is hitting 240, that does seem too high. The head on my engine hits 203-ish on a hot day, with the factory FJ62 188F t-stat.

When the engine is really hot, the worst thing you can do is shut it off. Best to shift into neutral and run the engine at 1500 rpm (or something more than idle), turn on all the heaters and heater fans, and perhaps open the hood. That will cool the engine most quickly.
 
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I would double-check the temps by using an IR Temp gun on the head (engine off - IR guns DO NOT like air flowing past them from the engine fan). If your head is hitting 240, that does seem too high. The head on my engine hits 203-ish on a hot day, with the factory FJ62 188F t-stat.

When the engine is really hot, the worst thing you can do is shut it off. Best to shift into neutral and run the engine at 1500 rpm (or something more than idle), turn on all the heaters and heater fans, and perhaps open the hood. That will cool the engine most quickly.

Oof. You're totally right. The coolant flash heats since air stops moving and stops circulating. I think I panicked.

IR gun has been consistent with my aftermarket gauge. At least in the same ballpark give or take 5%.
 

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