overheating problem

[gmc7286chevy]

ok, lets see who can figure this one out.
My radiator sprung a leak and caused my ride to overheat while i was driving. I replaced the thermostat and repaired the radiator. Yesterday after i got home after a 50 mile trip, i noticed water was flowing back into the overflow tank. It sounded like boiling water in the overflow. I hope its not a head gasket. I will do a compresion check to make sure.

[rage'nrat638]

did the temp. gauge say it was hot (i dought it) sounds like a bad
radiator cap. try one with the lever handle first them you will know
the status of your cooling system barring you did not get a bad
t-stat. MARK

[Senor_paco]

That happens when you have air in the system. It takes a little while to purge. when your truck gets hot, the steam vents throught the coolant tank, making it seem as if it is overflowing, but it's just equalizing the pressure. Then when the system cools down, it has a vacuum, and in turn draws coolant from the tank to fill the void. After a couple of cycles, your cooling system should have most of the air out of it. Just remember to keep your overflow tank full! You'll need to top it off in the moring the first couple of days or so.

[Blue Beard]

If you think your problem is resolved...........do yourself a favor.........get some good flush to go through the system. hopefully the system is clean.

[gmc7286chevy]

You dudes are too smart. I think air in the system was the problem. Thanks!!

[gmc7286chevy]

I spoke too soon. Around town its ok. At highway speeds after about 20 miles it overheats and boils the water out. Too much pressure builds in the system. I think its a head gasket.

[gmc7286chevy]

any other guessers?

[Mike76251]

It indeed sounds like a head gasket to me.
I am sorry to hear that.
It apparently got hot enough to warp the heads and blow the gasket.
You may need to have your heads serviced as they are no doubt warped now. If you try just a new gasket on it it may just happen again.

I once had a car ('84 Buick Riveria work-ride) that would overheat so bad that it would lock the motor up. The temp. sender went out the second time it overheated.
It did this seven or eight times and did not seem to harm anything.
I would even coast into a gas station and pour cold water from a hose into the red hot engine. NEVER do that kids!!!!!
This thing had 400K miles on it when I sold it and it was still going strong.
I had so much respect for these boats after owning that one that I found a NEW 1985 and bought it a few years ago.
Like I need more cars!!!
Moral of the story is that some cars will tolerate more abuse than others.
Small Block Chevys can take only a moderate amount of overheating if they have cast iron heads. If you have Alum. heads forget it, They warp on the first overheating "event".

You want a Chevy engine you can overheat everyday?
Get one of the old V6 305ci engines they used to put in our trucks way back when. The heads weigh the same as a Big Blocks' and they just laugh at 400 degree temps.

[Senor_paco]

didja think to check your ignition timing? Sometimes if it isn't advanced enough, at high speeds, it's not as efficient and generates a lot more heat. Sometimes if you distributor advance wieghts rust, you'll get that problem, since the ignition won't advance mechanically, just by vacuum. try playing with the timing a bit before taking the top off, just to be sure.

[Senor_paco]

could be the thermostat isn't opening all the way, just partially, enough to allow the lower speed water through, but causing backpressure at higher speeds. Replace it with a nice 195 degree unit. A few bucks here versus the time of a head gasket. If it is the gasket, then you can know for sure. Oh, if you feel it is your HG, is your engine losing coolant through the tailpipe, or when it is idling and you have the radiator cap off, do you get bubbles? You wanna make sure before you do a lot of work you might not have too Lemme know how it turns out!

[Senor_paco]

My money, IMHO, is NOT on the HG. I've been working on old cars for almost 30 years now (30 years? Jeeze!!), and a majority of overheating problems are caused by something else.

[87 STEPPER]

Im with marksdoor69 & senor_paco replace the rad cap if you haven't done so allready.

It's too easy and cheap not to do befor tearing apart the top end.

Good luck

[J-Spec C10]

I remember hearing about an additive that you put into your coolant that changed color if there were exhaust gasses in the cooling system. Unfortunately I have no idea where you can get it.

Ask around, maybe someone else will remember.

[PHOENIX]

Check your timing
Check your air to fuel ratio (carb)
Has you checked the water passages in the motor, are they clean?
How clean is your radiator inside, can you see alot of deposits when looking down into the radiator through the cap hole?
Changing cap wont hurt anything.
It is normal for coolant to go back and forth to the overflow tank.
The overflow tank is not there for overheating, it is there for pressure purposes. I suggest that you keep it at the recommended line. I fill up the radiator with 50% coolant and distilled water then start the truck. I run it for a few minutes and watch my gauge. Once it cycles the first time I add whatever is needed, cap is off at this time. I put the cap back on and fill the overflow up to the line, then its ready to go.

Is your water pump, pumping?

[CT-Truckster]

Ahemm, I'll let you guys know what the problem is, apparantly i'm gonna have to go over and figure it out for him.