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Overheating issue - absolutely stumped (Done almost everything)

The rad I have doesn't have a coolant temp sensor plug. But coolant was topped up. I still can't believe the running temp. It was 21 celsius out today and the car was idling at a light at 218 degrees. So I get home and decide to crack the bleeder & absolutely nothing is coming out. Not a drop like the coolant isn't circulating. wtf... Also the rad cap remains moderately warm at best although temp says 210-218... something is up!
 


One thing I don't like about these cars is the coolant passages in the head gaskets. The cooling jackets in the engine are huge but the head gasket passage is about a 3mm hole. If these get clogged you'll see what you're seeing. I believe GM did this to achieve a certain coolant flow rate throughout the engine.
 
I 've been using the Napa Superstat (by Stant) for years without any problems. These are high quality thermostats. The part # for the correct 180 stat is 531080.
 
Water pump and t stat replaced. T stat has been replaced a few times with different brands and it has 6 holes drilled. Tearing motor down to check out coolant passage would suck huge ass
 
The only thing the "hole in the t-stat" mod does is let any air that is trapped in the block escape when the engine starts. If your temperature gauge reads above the t-stat opening point, and the upper radiator hose is not hot, it is possible that the t-stat is not opening, or the water level is low.
 


Elite6 said:
Water pump and t stat replaced. T stat has been replaced a few times with different brands and it has 6 holes drilled. Tearing motor down to check out coolant passage would suck huge ass
Click to expand...

LOL

Last resort man.
 
Radiator is probably toast. It's not removing heat efficiently.
Or you have air in system.
You already have what, new t stat and water pump. So not much left
 
i would go to a shop and ask them to use a temperature gun and see if youre really running hot, most will do it for free then youll know for sure.. if you are and after all the parts you have put in maybe a crack in the head?
 
ive had water pumps that have failed in the first week.. the still move some coolent but not like they should so dont count that out even though you replaced it but you had this problem before that so i doubt its that.
 


Oxalic acid flush, created something when neutralized.... Interesting thread on doing an acid flush. Just finished doing one. I picked up a 1 1/4 steel barbed coupler and installed in the upper radiator hose, Makes for a quick drain hook up with a corrugated hose, both from Home Depot. I took an old 195f stat and drilled four 3/32 holes in it and installed. Filling radiator with a garden hose with engine running and a drain hose connected to upper radiator hose. During the acid flush with big fan fuse out, I was able to get up to 210-220F. Ran the acid for about 1 hour, then flushed with water. Flushed with neutralizer(baking soda) and once more with water.
 
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