old and new thermostat won't open?
 

Hi guys,

I have a 98 s10 i swapped a 100k mile 2000 silverado 5.3 into.

using the stock silvy clutch fan and the stock s10 4.3 radiator, I am having major overheating issues.
BUT, i think the fan/radiator have nothing to do with it, as the symptoms appear to be a stuck closed thermostat.

symptoms were. cold upper rad hose. boiling noises.

so i replaced the t stat with a brand new one.


same issue.

cold upper rad hose, boiling noises, but the rad hoses are definitly pressurized.

watching my aftermarket temp gauge (not tested to see if it is good or not, but assuming it is good) the temp stays pretty steady at 180 until it suddenly starts to climb all the way up past 220 until i shut it down.



so, why is it doing this?
how do i fix it?

must bleed a lot of air out of the system.

what's the best way to do the bleeding? never had an engine need so much effort in getting the cooling system purged.

i always drill an 1/8 inch hole between the center and outside of the thermostat, this lets air come from the engine easy to bleed.

^ Yes. A small hole will prevent an air tight seal without allowing too much coolant through

sooo new issue. no more overheating, but now temps will not get over 120F even under long hard driving.
yes air temps are well under freezing.
but with a working t-stat it should get up to running temps right?

after the drives, upper rad hose is warm, not hot to the touch, and lower hose is lukewarm/cold.