Over heating FJ62 - It's a puzzler... (yes, already scoured other threads...) (1 Viewer)

[89FJ62]

Subject: '89 FJ62, 166k miles. Well maintained RE oil changes, tranny flush and fluid changes, etc.

She began overheating last summer on the highway. Seemed to have a coolant leak as the overflow tank would get sucked dry once a week or so, then it'd overheat. Couldn't locate a specific leak, then checked the water pump weep hole - dripping. So I replaced H2O pump - also replaced the thermostat while I was at it. Still hot - and not losing water. Radiator flows like a champ and is not blocked.

The fan clutch felt like it had some grab (though I haven't heard it "roar" for a while) but I replaced it anyway with a NAPA unit. Still hot. On advice from local auto shop, had them install an HD tranny oil cooler...

It's still overheating with new pump, thermostat, oil cooler, rad flush and fan clutch. It'll idle around town okay, but will heat-up under the slightest load going up Seattle hills, the the gauge stays at 3/4 or just under the red mark. Will cool to 1/2 mark and stay there if it's not under load. IR temp scanner reads 225 at the thermo housing, 180 or so at the bottom of the rad hose outlet.

The truck seems to run fine, albeit the gas milage had dropped over the last month or two to about 8/9 mpg when I was getting 10/11.

It's not pinging, so I have not yet checked the timing. Seems to run/idle smoothly.

My wife says it's time to lead her out to pasture and put a bullet behind her ear as return on investment is dwindling... I don't wan't to drive a plastic truck. Suggestions?

 

[Michael Hanson]

gauge itself,radiator. Mike

 

[Rigger]

gauge itself,radiator. Mike

X2. If the only evidence you have of overheating is the factory guage, consider that it may be the guage itself. It may be that the guage is telling you it is hot, and it is not actually hot at all. Try going over the motor with an infrared thermometer.

Edit: Doh! Not sure how I missed that you wrote that you had used an IR scanner. My bad!

 

[fliphkd778]

If the gauge says its getting hot, then I would probably say it's true. Easy things to try are... removing the thermostat completely and making sure the water pump is building pressure. Test the thermostat while its out. You might have a large bubble in the cooling system if it's sucking the overflow dry.
When filling, start the truck up cold without the radiator cap. While it's running, pour in as much coolant as it will hold and replace the cap. DO NOT shut off the engine then put on the cap, or else it will erupt.

 

[krookedpandas]

When you refilled the system did you take the steps to get all the air out? Running it with the heater on full blast helps move the air out and if that doesn't help then try burping it.

Good thread on burping:
https://forum.ih8mud.com/60-series-wagons/189393-my-burp-setup.html

One thing I didn't notice in that thread is that you need to fill the funnel up with coolant so it is the highest point in the system. Takes a while but you should see bubbles come out.

 

[slcfj62]

If you are looking for what to try next here is a thread where everything even remotely related was replaced, so I would imagine your problem is somewhere on this list.

https://forum.ih8mud.com/60-series-wagons/161145-unsolved-over-heating-impossible-solve.html

Oh, and replacing the fuel gauge is what fixed it, so make sure you are not chasing a ghost before you start replacing expensive parts.

 

[Randy88FJ62]

When you installed the water pump did you use the paper gasket? I have not done this personnally but I have seen it talked about a lot on this site as an issue that can cause over heating.

Don't shoot your truck, I'll take it if necessary to save it from your wife.

 

[Bryan062087]

radiator

 

[Miloslavich]

I experienced a similar problem in my 60, that didnt go away till i replaced the radiator as well. I did the fan clutch, water pump, and nothing helped till i did the Rad. - which kind of happened by accident but turned out for the best.

I'd try a lifetime warrantied Rad from Auto Zone, if it ever fails just take it back.

hope this helps.

 

[89FJ62]

If the gauge says its getting hot, then I would probably say it's true. Easy things to try are... removing the thermostat completely and making sure the water pump is building pressure. Test the thermostat while its out. You might have a large bubble in the cooling system if it's sucking the overflow dry.
When filling, start the truck up cold without the radiator cap. While it's running, pour in as much coolant as it will hold and replace the cap. DO NOT shut off the engine then put on the cap, or else it will erupt.

Typical overheating scenaio: will run on first gauge hashmark, then steadily climbs to 7/8 mark while under light load going up residential (steepish) hills. then stays at 1/3-12 mark until put under load again.

Just tested for Hydrocarbons in coolant - negatory.

Timing is dead-to-nuts on (PITA BTW, getting to the timing marks...)

Topping-off coolant with funnel in rad neck technique while running as I write this (Puked a bunch out when taking rad cap off for Hydro test at neighborhood shop).

Checked Rad flow by removing bottom hose - the fluid DUMPED OUT - so flow doesn't seem to be an issue.

Also re-routed the tranny cooler to an HD external unit - no effect. Radiator is clear of debris, etc.

I DID MAKE A PAPER THERMO HOUSING GASKET and used liberal amount of permatex copper when I replaced the thermostat, but I'm getting the same result as before I replaced the original thermostat...

 

[Bryan062087]

Taking off bottom coolant hose is not the way to check radiator flow, I wouldn't think. lol

 

[NYC FJ62]

When truck is overheating, are both ends of your radiator hot ?

I'd lean towards air in your system. It can be a b!tch and cause headaches....

 

[89FJ62]

Taking off bottom coolant hose is not the way to check radiator flow, I wouldn't think. lol

An ASE certified mechanic with 20 years experience tested the system, and made that anecdotal comment RE flow.

Temps read 225 at therm housing and 175 at bottom hose.

I'm Uber-burping/filling the system per experts here, and I'm buying/installing an OEM thermostat (last one was from NAPA, but you never know)...

 

[fliphkd778]

The thermostat can be easily tested with a pot of water on a stove with a thermometer... should open at 180-190 degrees.

 

[satchel]

I had same problem with overheating when going up hills and such. Was fine while idling. Changed out tstat, fan clutch and flushed radiator. None fixed it. I finally decided to do the autozone radiator and have had 0 problems since. It looks like you've done most of what you can do besides changing out the rad. Give it a shot, especially before you put a bullet in it!

 

[satchel]

I may be missing something, but 225 on your top hose seems like it would be high to me. I've never actually done a reading, and it makes perfect sense that your top hose is hotter than your lower hose, but if your tstat is opening at 180 to let the coolant flow to the radiator I would assume the temp of the hose connected to the tstat should be around 180-190, not 225. Or do you have a really high temp tstat? Again, I'm probably missing something, but I figured it would be closer to the temp that the tstat should open at.

 

[drjones]

I had all the same story and put in a new rad too. What finally fixed it was a desmog of all things. Apparently a failing smog saps puts enough strain on everything to cause the temp to rise...

 

[ntsqd]

Been a while since I read that other thread, but a partly plugged exhaust will cause overheating.