Overheating problem - '81 FJ40 (1 Viewer)

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I could be wrong on this, but from the pictures @mdwhiting posted he does not have the temp sender in the T Stat housing. I believe his temperature sending unit is on the right rear of the head in his picture in post 9.
Correct, mine is there as well.
 
You must have a sender somewhere. This is a 1981 general market diagram. Not sure your exact model so this might be off. But it looks like 2 sensor holes in the thermostat housing. If they are both plugged, then it’s been moved. Looks like it’s the same PN as the US models, 83420-20020. But I may have the wrong model.


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Thanks for sharing this - what website has these drawings? My model is FJ40RV-UC. I see this is for L-KC....
 
@mdwhiting your temp sending unit is on the driver side rear of your head. Put an IR GUN on it to get your real temp.
 
Interesting. Same sender PN, BTW.


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Also @mdwhiting just to cover all of the bases…go to the hardware store & purchase some FOAM INSULATION STRIPS, & close the gap between your fan shroud & the radiator itself (look closely at your picture in post 9).
Yours isn’t ‘that’ bad…but every little bit helps.
 
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just wondering, is the fan on the correct direction?

the fan is sitting too far inside the shroud, as stated above the fan should be right in the round section of the shroud, slightly sticking out to the rear of the shroud
 
where does Not having the factory OIL COOLER Option topic fit into a factory A/C equipped 2F FJ40 topic ?

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I had several experiences where I could not figure out both of my 40's(79 & 82 U.S. spec models) were overheating but at different times.

So here is what I learned, I had bad fan clutch, easy to check, should freely spin but as it warms up, the clutch portion will lock the fan and it should spin with the engine. If you don't this don't worry about it. I found a hose at the oil cooler rubbing on the splash guard to the point it had a hole. I could smell the coolant but could pin point it, anyhow, replaced hosed. Another time, for some reason the thermostat stopped working, I diagnosed it with a IR thermometer. I think overtime but sometimes over heating them for long periods will hurt the integrity of the thermostat and trust me they are not cheap. I also cleaned all the hose ends and fittings...that really did not clear my issue but improved it a little bit. Water Pump has not failed yet. Something else I noticed and surprised me when I found it was after the engine warmed up with the radiator cap off and engine running, the cooling would be bubbling out. Ended up being a bad head gasket. I had no water coming out the muffler or water in the crankcase. So the main reason why overheating occurs is there could be a leak somewhere in the system. Or the proper flow is not adequate...clogged/corroded cores on the radiator(sometimes its cheaper to replace the radiator than to have it rodded out, rust fins in the water pump, bad thermostat or to much gunk. I  think at point I would also consider putting some kind of stop leak in powder form. Some of the radiator shops use it. It looks like burnt flour. Personally don't like using it. Something I noticed if I'm a quart short of oil it runs a little warmer than normal. Anyhow, hope you find the overheating issue.
 
just wondering, is the fan on the correct direction?

the fan is sitting too far inside the shroud, as stated above the fan should be right in the round section of the shroud, slightly sticking out to the rear of the shroud
Yes, fan is in correct orientation. I will try the insulation stripping to better seal the shroud. Might be a spacer I can remove to pull the fan back toward the engine. Will confirm.
 
The parts diagram above shows an oil cooler starting in 1980/08. The OEM oil cooler is over $700 now. I suspect many have just been deleted over the years due to replacement cost. But who knows in the market yours came from.

I’ve heard both arguments on whether you need them. Toyota certainly thought you did as speeds/RPMs increased or they wouldn’t have installed them. On the other hand, modern oils are WAY better. Not sure there is a clear answer. My engine has one and I keep it on. If I didn’t have one, I don’t know that I’d add one. But that’s just me.
 
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Toyota Matt is right, an oil cooler should help.

I bought a new OEM oil cooler and all the associated hoses and clips. Yup, over $900 with our 10% sales tax out here in WA. Happy to sell the old one for next to noting if you want it. That being said, there’s no reason you couldn’t use a generic oil cooler if your not worried about keeping it original.
 
I had an overheating problem that sounds a lot like yours. Ran cool on short trips (1 hour or less), but overheated on long highway trips. Turned out to be a partially clogged radiator. I replaced the radiator and never had the problem again.
 
Have you drained at the block drain? It's the lowest point of the cooling jacket where crap likes to settle.
 
One more possibility that hasn't been mentioned yet - check your ignition timing, and more importantly, check to make sure the vacuum advance is working. Retarded (i.e. not advanced enough) timing will cause it to run hot. If it is the vacuum advance, you would notice it a lot more on the highway than just running around town.
 
Echo @1911 and make sure your valves are properly adjusted!
 
Yes, have shroud. I did check temperatures today after the drive home. I used a generic radiator cleaner, drove for about 20 minutes and checked temps. (no thermostat installed). Here's what I found (with engine/fan running):
Thermostat housing: 162 F
Upper radiator hose connection: 163 F
Lower radiator hose: 140 F
At these temperatures, the temp gauge was just a little right of vertical - not running hot. I find that if I am just driving around town at lower revs, no overheating issue. Any kind of sustained driving at 45 mph or more it is a problem.
I removed the upper radiator hose from where it enters the radiator to see how the water pump was working (while engine running - slowly and carefully.....) and a hose filling the radiator - the hot water came out in gushes (it wasn't regular, steady flow). It would come gushing out, then stop, then (about 5 s later) would repeat.....thoughts here? Maybe it was cavitating because I wasn't feeding water in fast enough? Or bad water pump? In my first photos you can see that PO patched it somehow.
If the water pump is cycling coolant from the head, like when the thermostat is closed, then that might explain why no coolant is running into the radiator. I'm not sure about w/o thermostat installed. Either way, I hope that cold water wasn't being added into the radiator, then pumped into a hot engine; the manual warns against flushing (hose attached to filler neck) with cold hose water.

If the engine was actually running hot, I'd suspect sediment in the radiator. Generally, my water temp needle is just left of vertical, the '75 Owner's Manual suggests that it can go as far as the second line (just right of vertical). FJ55s have a different gauge. I'd seriously consider a new radiator, as the heat-exchange aspect of it is a bottle-neck in the system, especially with time, the smaller passages could easily be obstructed. I'm not familiar with water pumps, but, maybe the rotor isn't pushing water around efficiently for some reason. Engine service is pricey, complex cooling system parts, like radiators, thermostats, radiator caps, and water pumps are relatively inexpensive.
 

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