Cooling / Overheating

[jHanratt]

Has anyone had a failure of the electrical sensor which turns on the engine overheating light on the 92 7.3 liter. Do they ever turn on the light prematurely? The warning light on my truck doesn't seem to agree with the engine heat gauge. Which one is more trust worthy? I have changed a LOT of variables all at once here and I am just wondering what should I do if anything?

My unit is a 92 F-350 4x4 7.3 liter idi with a Banks Sidewinder, Monster Exhaust and an E4OD with Trans Command. It is a 28' motorhome so it is ALWAYS working hard. I am the third owner. The second owner knows nothing except how to turn the key and where the diesel goes. The original owner had it custom built and put in the modifications but he has passed away so I am figuring out what I can as I go.

I took it on a month long 4,000 kilometer holiday this summer and pulled my 6,000 pound boat the whole way. Total weight is about 16,000lb. It ran great for the whole trip until.... 80 kilometers from home I pulled a very steep grade from Ashcroft to Logan Lake on a 36 degree celsius day. She overheated immediately on the first part of the very bottom of the hill.

The Coolant Temp light came on but the temp gauge read between the M and A on Normal. According to the gauge I was not overheated yet. It smelled hot but the engine compartment is oily and dirty so it's hard to tell because it smells anyway. The Pyrometer was at about 1100f which is normal for hard pulls in this rig. I did not want to risk a boil over or damage so I switched from AC to full heat and put on the rear heat (bus heater). I shifted down through the gears and kept moving to keep air flow through the rad. I ended up in 4 low and second gear all the way to the top of the hill. Every time I up shifted the light would come back on so I just settled in and crawled up the hill. I kept the pyrometer low at about 500f to 600f.

I stopped at the top when it levelled off and checked the cooling fan because I had not heard it lock up. It was stiff but not locked but by then it had cooled from running a ways on level ground.

Since then I have heard the fan clutch cycle in and out as needed. At the time it did have a small leak in the heater hose which supplies the rear heat so it is possible it could not maintain pressure in the cooling system.

When I bought it I noticed the bumper was at the bottom of it's mounting holes and I moved it up for looks but now I am wondering it that was done to allow more air flow into the rad. The PSD's have extra air holes in the front bumper to allow air through the bottom of the rad.

So I fixed the heater hose leak first. Changed the coolant and confirmed the fan clutch is working. I also bought the trim piece from a Power Stroke front bumper and cut out the air flow holes to allow extra air flow and moved the bumper down a little to allow more air flow. Of course it's cool now so I won't know until next summer on my next vacation if I fixed it or not.

Once again:
Does the low coolant light sensor ever fail?
Which is more likely to be accurate the gauge or light?
Is there anything else I should check or do?

Thank you all in advance for your help.

[LMJD]

I fought the same problem when my truck was new although maybe not quite as hot as yours on the hard pulls. After making sure I had no cooling system problems, I added the black strip and cut the bumper holes and in my case that cured the problem. I had some thin aluminum sheeting laying around and I made an air dam from the bottom of the front bumper to the bottom of the rad support so most all the bumper hole air had to go through the rad. Back then I talked to the full time 7.3/6.9 mechanic at my selling dealership and he felt the Ford cooling systems were marginal anyway and like he said, you add a turbo system and anytime you increase an engine's horsepower you put a higher demand on it's cooling system.

By your post, I guess I'm wrong. Back then a guy at work bought a '92 7.3 and I thought sure his had the factory bumper cutouts. That was the year they made the body change.

[jHanratt]

One problem with this rig is not having the original owner to answer any questions. She had a solid and plain front chrome bumper but the truck cab has been re painted so you never know it may have been in a collision or maybe had the bad primer issue which was common in those years. Anyway I have cut the PSD holes and installed the bumper trim now. So I guess I'll find out if I beat the problem next summer.

Still would be nice to know if the coolant light or the gauge is more accurate. Maybe It wasn't even that hot?

Can anyone advise which would be more reliable?
Do they work off of seperate senders?

Thanks everyone.

[cdnsarguy]

Do the fan test on my photo link first.........

The overheat switch on the front lower corner of the left head I personally would believe, it is an on off switch. You could replace the temp sender on the flat surface of the left side of the block just in front of the head. They both require a good ground, so use of liquid teflon sealant VS teflon tape is my choice for a good ground... unless the new sender comes with the red thread sealant already.

You could test both seperatly by grounding the wire out, the result should be max overheat condition sent to the dash guage.

Check the lower coolant hose has the coil spring in it........ just squeeze it.

Diesel engine coolant temperature at the top of the radiator where hose attaches after high rpm or under load condition for 20 minutes should be (195-237*F) 91-114*C nice time to have a temperature reading point and shoot tool.