Overheating with new Rad and T-stat

[katugly]

So I replaced my OEM radiator that had more leaks in it then were repairable with a new one. Proper 3 core with HD trans cooler and such. The shop guy noted that the T-stat may be stuck open or not installed. I cracked open the housing and it did have a T stat in there but it was stuck open. I dropped a new Murry in place of it but the sonva bitch wont open. I pulled the upper hose and when the gauge on the inside is damn near into the red the upper hose is dry. I pulled the thermostat out and had the wife start the car with without it and it pumps out no problems. What would make a new T-stat that has been tested in water to be good not open in the car. What is the best way to bleed the system because that's the only thing I think that could be the issue is there is air trapped under the thermostat. 90 blazer with a 350 btw.

 

[Thunder]

Did you install the thermostat backwards/upside down? they wont open if backwards.

 

[katugly]

nahh its spring side toward the block

 

[4xcrazy]

I had an issue a few weeks back where i had a leak, refilled the radiator, and when i went out for a drive the next morning, it started to overheat, same type of situation, where the upper hose was cool to the touch,but everything else was hot.

I simply cracked the radiator cap (very carefully) and as typical, the pressure i guess sloshed and moved around enough to get the t-stat moving, or remove any air that may have been trapped anywhere. I did not remove the cap completely, simply cracked the opening enough to let it breath for a quick second and got everything moving, all was fine with cooling since then and even now.

I was always under the assumption, that these systems are suppose to be self bleeding, as the reason the radiator cap is at the highes point in the cooling system.

 

[clandr1]

I've also heard a good way to bleed is to take the cap off (cold radiator) and fire up the vehicle. Let it idle for a few minutes and it's supposed to bleed itself, then when you stop seeing bubbles in the fluid you can top off and put the cap back on.

 

[Cornfield creations]

I've also heard a good way to bleed is to take the cap off (cold radiator) and fire up the vehicle. Let it idle for a few minutes and it's supposed to bleed itself, then when you stop seeing bubbles in the fluid you can top off and put the cap back on.

I agree. For safe measure I also drill an 1/8 inch hole in the thermostat to allow any air trapped underneath the get through.

 

[katugly]

Well I took the old one out and some how the pin that rides in the middle of the whole assembly was out of the top portion. I took a new one drilled the hole so i can bleed and stuck it all back together. Top hose is hot and "stiff" as it should be but the temp guage on the inside reads all the way to the end of the scale.

Now here is the other part of the equation that may make the differnce. I used a temp guage out of Oaknights blazer and put in my VSS cluster. His has no temp marks on it and mine did. Could it be that the later guage has a differnt sweep than the one out of Oaks blazer. His is a 87 if I recall.

Current Style that is in the truck

Style that was removed was the one with numbers on it.

 

[4X4HIGH]

It is probable that the senders are different between both styles of gauges.

 

[katugly]

See thats what I thought too but looking around the temp senders for the 70's - 90's are all the same part number. My thought is that the guage its self translates the resitance differnt.

 

[4X4HIGH]

See thats what I thought too but looking around the temp senders for the 70's - 90's are all the same part number. My thought is that the guage its self translates the resitance differnt.

That could very well be as well. There was a thread on here not long ago about a resistor on the back of a gauge but I don't remember which gauge it was on (might have been fuel gauge).

 

[katugly]

So i have the super El-cheapo temp guage that came with the truck still im going to throw it in there tomorrow and see what it reads. I dont see how it can be over heating with a brand new radiator and the cleanest fluid I have ever seen.

 

[4X4HIGH]

You haven't changed the water pump have you? The reason I ask is because a serp belt system uses a reverse rotation water pump, clutch and fan blade.

 

[katugly]

no its just the pump that came with the truck. It was cooling fine when it was full of fluid with the old radiator. I just had to replace it becuase it was leaking from every where. I used Oaks guage becuase I didnt like the cheapy one that was in there from the PO. Maybe that was the reason he changed it was becuase it wasent reading correctly.

 

[ryoken]

yet another reason every wrench turner should own an IR temp gun... one of my most valuable tools at work... can be had for about $50........

 

[katugly]

I have two of those but they read surface temp. What would I shoot to read the coolent temp in the head of the motor. Seems that the sensor itself would be a poor indication of coolent temp inside. Im just not sure where to take a reading at.

 

[ryoken]

the base of the therm housing is always the most accurate reading of what a motor is running...

 

[Cornfield creations]

the base of the therm housing is always the most accurate reading of what a motor is running...

Just a thought, wouldn't the aluminum intakes dissipate heat quicker showing an inaccurate engine temp. Sure the coolant inside would be hot, but not as hot as the coolant in the jackets in the heads?

When I was trying to find my coolant issue my intake and heads read differently.

 

[katugly]

I need to do what some one did on here and put a guage tapped into the thermostat housing. That seems like a super smart way to have a failsafe.

 

[ryoken]

any heat disappation thru that 1/2" of cast is beyond minimal at best... it's really just transfering the heat thru to the outside surface, which is what your reading... before it could actually disappate any heat... head surfaces can be inaccurate cuz it's being affected by exhaust...

and obviously thats even quicker with AL.... but even an iron intake will transfer the heat for an accurate reading way faster than you would think....


let's put it this way.... it's a standard practice in my line of work.. an IR gun is in my tool bag on every test run.... multiple readings are taken for various reasons, exhaust, etc, but thats the spot for accurate overall motor coolant temp...

 

[Cornfield creations]

any heat disappation thru that 1/2" of cast is beyond minimal at best... it's really just transfering the heat thru to the outside surface, which is what your reading... before it could actually disappate any heat... head surfaces can be inaccurate cuz it's being affected by exhaust...

and obviously thats even quicker with AL.... but even an iron intake will transfer the heat for an accurate reading way faster than you would think....


let's put it this way.... it's a standard practice in my line of work.. an IR gun is in my tool bag on every test run.... multiple readings are taken for various reasons, exhaust, etc, but thats the spot for accurate overall motor coolant temp...

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