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Overheating Problem

8K views 23 replies 9 participants last post by  LMJD 
#1 ·
My 94 IDI overheats when I'm pulling a load uphill. Where do I start looking for the problem? There are no leaks in the cooling system. I've had this truck for 8 months now and have already put $2400 into it but I expected it since it has over 300k miles.
 
#2 ·
Are there bubbles in your coolant tank when it's running and up to temp? Is your upper radiator hose hard when its hot (it's supposed to be if radiator cap isnt sealing it wont keep coolant under pressure and will boil). Do you have a real gauge or the factory gauge? What does the inside of the radiator look like when looking through the radiator cap? Is your clutch fan functioning? If you hav a real gauge, without a load does the thermostat always maintain 180-190?
 
#3 · (Edited)
I have the factory temperature guage. The clutch fan engages very little when it gets hot, doesn't stay on while it's hot. When warmed up the temperature hovers around the center of the guage during unloaded driving. I will check all those other things. Thx
 
#4 ·
Saying it overheats pulling a load uphill doesn't mean a thing without knowing what temp your talking about.

The fan kicks in hi speed if you want to call it that, it kicks in at around 135*F to 140*F from the air thru the radiator that heats the coil spring in the fan clutch. Normally the fan will only cycle for 1 to 3 minutes to cool down.

Without a real gauge to indicate the head temp, your just guessing that it's overheating.

If someone installed other than a Motorcraft or IH T'stat, that could be a problem. IF it's a Chine made, they are prone to have the supports break off and not control the coolant flow correctly. See pic to see the three supports, thin metal strips to dome. Shown is the correct T'stat.
 

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#6 ·
The temperature needle went past the normal range to the red and the overheating light came on and I could smell coolant so that's how I figured it was overheating.
The Tstat would probably be a good place to start. I'll get one from Ford parts and replace this one. Can you recommend a good sealant to use for this?
 
#7 ·
I use Three Bond 1184 for everything. It seals up within 10 minutes, well you need to let it tack up for 10 minutes, then mate surface and its ready for oil/coolant in 10 minutes. Be careful with the thermostat housing, soak it in Kano Kroil or something, i did and still broke one of the bolts, i was lucky enough through soaking after removal to get the broken stud out with vice grips
 
#8 ·
Hmmm maybe I should go ahead and get 2 new studs while I'm at it. It does have a lot of miles on it. Thx
 
#9 ·
Well they are actually bolts, they became studs when I broke them haha. I just replaced then with 1.5 or 2 inch 5/16 of 3/8 grade 8 bolts. I can't remember the exact size I always have a few bolts laying around. I'd invest in some aero kroil, it's expensive but by far the best penetrating oil I've found, it even smells nice.
 
#12 · (Edited)
What mechanics have used through the years for this and most all other applications is 3M Weatherstrip Adhesive on either the block or thermostat housing to hold the gasket in position, and a slight coating of the Permatex Aviation sealer (brown stuff) on the other side of the gasket. Actually if the surfaces are clean, no sealer is really needed, no reason why it should leak.
Unless someone has installed the wrong thermostat, it's a greater possibility your overheating problem is your fan clutch. When pulling hard at at least 2400 RPM or more, you should definitely hear your fan clutch lock up and roar when your gage needle gets to the upper area of the "hot" range. Mine has always done so, then the needle slowly creeps down to the lower "cooler" middle of the range while the fan is locked during long heavy pulls like going over the Continental Divide. And don't be led astray by this type of incorrect crap from another IDI site:

"once your speed is past 30-ish, the fan is useless anyway, as the wind over the radiator is more than a fan would pull over it. the fan does the most good in stop-and-go traffic, and when just stopped. but even climbing a steep hill at 35, there's plenty of airflow a fan isn't going to make a difference, but water flow sure will!"
The guy's obviously never towed much or definitely a flatlander who never saw a mountain.
 
#13 ·
My truck was slow to warm up, which I realized later, and began to get hot towing on hills. Half way stuck non Ford thermostat was the problem.
 
#16 · (Edited)
I pulled the thermostat out and it was a motorcraft part but it was in 2 pieces. It was stuck but it was stuck open so I replaced it with the motorcraft tstat and made no difference. Ever since I bought this truck a year ago the overheating just gets worse and worse. I have noticed a slow but steady coolant drop in my radiator but never saw the leak but it is dropping much faster in the past 2 weeks and I put 2 gal in it yesterday and today it is below the fins again in the radiator but I can see the leak now. It is coming from the front of the engine with a steady stream leaking directly from the crankshaft. I cant see it coming out of the water pump but Im assuming its leaking from there. Could it be weak flow from the water pump causing all this overheating? I'm going to go ahead and replace the water pump. Is it hard to replace the water pump? Should I get the motorcraft pump or autozone? Are there any left hand threaded bolts? Do any of the bolts need rtv on the threads? Any tips?
 
#17 ·
Biggest thing is the bolt lengths. The top two are a specific length so they don't hit the timing gears. I wouldn't use the AZone "house" brand myself but that's just me.
 
#19 ·
Are there any left hand threaded bolts? Do any of the bolts need rtv on the threads? Any tips?
No left hand threads except the fan clutch. Don't use Teflon tape on any bolts. Use a liquid sealer on the bolts.
 
#22 ·
Just another thought. Had a truck in my shop years ago that overheated under a load. After allot of troubleshooting, turned out to be that one of previous owners must have used block/head gasket sealer and it blocked up part of the radiator. It took a long time to flush the cooling system to get it back to normal but it did solve the problem.

This was always my sealer of choice for bolts that extended into the cooling system. In the old days it used to smell like Fruit Loops! -

http://www.amazon.com/Genuine-Fluid-12346004-Teflon-Sealant/dp/B000QIXFEE
 
#23 ·
Geez, look in any Auto store lots of different bolt sealer. Teflon paste but never the tape.
 
#24 · (Edited)
Most all mechanics use the Permatex Aviation Sealer (the brown stuff) on bolts in situations like this and Teflon paste or tape on hydraulic, pipe, etc, fittings. The aviation sealer is also commonly used to seal and hold gaskets in place. There's a correct way to apply the Teflon tape so it doesn't get into the hydraulic or fuel system. (A real shocker for some on the "other" site)
 
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