overheatin chevy

[magnet]

one of my apprentices has a 95 chev halfer 4x4 with a 5.7 in it. overheats every day once it heats up a barries the temp gauge it cools down. and runs fine. been doing this for abouyt 1 yr now does it all the time. he has replaced 2 rads, water pump and 3 thermostats and 2 rad caps. any suggestions??? not sure where to lead him to repair it .he has replaced everything. and issue is still there. he has checked it and it is definitly overheating when the gauge says it is. so not just a faulty sensor or gauge.

 

[Summitric]

Has it actually boiled over??? And spewed coolant out the overflow tank?

 

[magnet]

yeh he says it did a couple times this summer. does not use any coolant as long as it doesnt boil it out.

 

[teeroy]

If he has done all that, i guess asking if he made sure the cooling system is completely full would be silly.....I made the mistake once of not letting it run long enough until the thermostat opened and never got it full....it did the same.

 

[magnet]

If he has done all that, i guess asking if he made sure the cooling system is completely full would be silly.....I made the mistake once of not letting it run long enough until the thermostat opened and never got it full....it did the same.

ya he has done that a few times already just seems to push it out after he fills it more. i told him to remove the thermostat and drill a small hole in the edge to let the air go past before it opens.

 

[Summitric]

Using a scanner, you should be able to access and read the engine temperature and see how that compares to the dash temperature guage. That would eliminate any possibility of the guage &/or sending unit.....

 

[magnet]

thnks ric i will try that too. never thought of that i have a code reader that has readout while running option on it i can use. see what happens.

 

[JBDoo]

It could be the wrong water pump on it. The old ones turned the other way before the serpentine belts came out. But I'm thinking it's a crack in one of the cylinder heads or a head gasket. They don't always put antifreeze in the oil when they crack. Get it warm with the rad cap off and watch for continuous bubbes and see how much flow comes out the core tubes when revved up a bit. The flow should come out the tubes and pretty much hit the side of the tank.

 

[Rockwerx]

It could be the wrong water pump on it. The old ones turned the other way before the serpentine belts came out.

That is one thing that I thought might be the problem. Also he could have a blockage in the coolant system. I have seen the bottom part of a rad cap come off and it will float around the system causing over heating problems depending on what ports it blocks coolant flow. I have seen this happen on cars, trucks and sleds with some poorly designed rad caps. It took us awhile before someone noticed the little disk on one rad cap was missing...we finally found it blocking off the center cooling port on a triple sled engine...after it had melted down a couple times of course.

 

[magnet]

That is one thing that I thought might be the problem. Also he could have a blockage in the coolant system. I have seen the bottom part of a rad cap come off and it will float around the system causing over heating problems depending on what ports it blocks coolant flow. I have seen this happen on cars, trucks and sleds with some poorly designed rad caps. It took us awhile before someone noticed the little disk on one rad cap was missing...we finally found it blocking off the center cooling port on a triple sled engine...after it had melted down a couple times of course.

thats what i was thinking was a blockage but after it heats up and thermostat opens it runs fine till it totally cools down again then it overheats till the thermostat opens and then all is good.

 

[Oldtrick]

Just out of curiosity, has he ever had the head gaskets done?
I don't think he has a leak or you would have white smoke all of the time and a loss a/f in the rad.
I did have a mechanic once who would screw up about every 5th time and put a head gskt in upside down and it closes the wrong ports, instant overheat, also found some puched totally wrong. So just a thought that it might be a head gst issue of sorts and try running a temp scan why not see if one side is way higher than the other??

 

[Polarblu]

Use a vacuum fill system, uses air venturie to put a vacuum on the system and then the system actually sucks the coolant in. there will be no air left. By what i have read you have a partial block in the flow and the air isnt getting totally out. This tool will fix it. If that dosnt work pull all the frost plugs and start borescopeing coolant passages.

 

[growly]

what brand of t-stat is he using? Did he replace all 3 with the same brand? If he did,try a different brand,had this happen one and went through 3 stant t-stats before I got a good one.

 

[OVERKILL 19]

Throwing a dart...clutch fan toast! Once she gets hot enough it engages and keeps her cool!