'82 Chevy G10 "overheating" at sustained higher speeds

Does it have a fan clutch? Have you changed it?

Bob

How did trans fluid get into the overflow jar? Maybe I misunderstood what you are trying to say?

the fan spins rest assured. I only brought up the part about the overflow bottle filling (after starting it up after a year or more) if in fact my overheating problem is not related to the coolant system, but the tranny possibly overheating (?). Question is if I flush and refill the system (it's got pure water right now, and no thermostat), and that doesn't do the trick, what then? I do suppose I should just get to it, but I had to put off a trip today, and it made me anxious.

Having plain water and no thermostat might be your problem. In any case restoring it to the way it should be, with a thermostat and the proper coolant can't hurt and could only help in figuring out what is wrong with the system if the problems persist.

Antifreeze not only lowers the freezing point but increases the boiling point. Removing the thermostat has changed the way the coolant flows through the system.

"Chris" wrote in news:1164505720.870677.240950 @l39g2000cwd.googlegroups.com:

I think you need to find out if it is really overheating, sounds like it may just be a sender or gauge problem. KB

"Chris" wrote: 82 Chev G10

Overheats at highway speed - anything over 40mph. Temp gauge needle pegs but if you stop for a few minutes it goes back down to normal.

I suspect it could be tranny related (clogged filter?). Fluid level is fine, but I notice that when I haven't run it for a long time (over a year) the fluid would drip out, and I'd let it idle for a while, fluid would rush into the overflow bottle after a while. When I replenished the tranny fluid, it would be fine. _______________________________________________

In order of highest probability:

Thermostat failed partially open. Deposits built up inside radiator. Leaves or trash blocking outside radiator. Fan belt slipping. Water pump impeller slipping or eroded. Exhaust mainfold too hot (burned valves) Trans fluid too hot. Anything else.

Good luck.

Rodan.

Bad fan clutch doesnt normally cause vehicles to overheat at speed. At low speed or idling in traffic,yes.

Overheating at highway speed is usually a restriction in coolant flow or blocked air path to radiator. I think he needs to find out first if it is really overheating or is getting a false indication.

I dont see the transmission being a likely problem, but stranger things have happened.

I had the fan clutch degrade on my S10. I would go out on the Hi-way for awhile and it would run hotter but still run. Then, i would come back into town and the temp would shoot way up and during a hot day the truck would actually miss and quit running. I felt the fan clutch and did not think the clutch was bad. My brother in law felt it and said otherwise. I changed mine and the problem went away.

There has been some cases of water pump impellers degrading on some cars though i have not heard of that happening on a GM truck. Might be worth it to take the pump off and change the thermostat

Bob

Pull what you can at a wrecking yard and start swapping stuff piece by piece, easiest to hardest. If you still can't find the problem, then it'll be in the engine block.

Come to think of it, it could be timing related. If I remember correctly, if the timing is too retarded the engine will run hot - something that would be more exaggerated at high RPM. You might have messed up weights in your distributor.

Put antifreeze (50/50 mix) and a thermostat in it and a new radiator cap. (only about $20 total) With plain water if anyplace in the engine gets the water over 230 or so (assuming the cap holds pressure) it will boil and the steam messes up the whole cooling system function leading to rapid additional temperature rise. If your cap is bad it just makes things worse.

seems to be some very useful stuph here. Thanks guys, I'll check it out ;)