Cooling systems talk and questions

[89Suburban]

Any of you guys ever see your engine temp spike after a cold start warm up then drop back down to operating temperature? Mine does that once the temp drops to a certain point, like down in the 20's and teens. I figured it was beacause the temp sensor for the guage is in the head and the head is getting hotter faster than the thermostat? Does that make sense?

 

[davbell22602]

Sounds like the T-stat is sticking.

 

[89Suburban]

I guess I'll find out after I do the intake gaskets and install the new thermostat. I thought it was just a cold weather thing.

 

[davbell22602]

I guess I'll find out after I do the intake gaskets and install the new thermostat. I thought it was just a cold weather thing.

My grand am did that in the summer and replacing the T-stat fixed it.

 

[Swims350]

I noticed with a mech. gauge compared to running it in an alum. intake or the head, the head indeed runs hotter. I had it jumps around when in the intake. When the t-stat would open it would jump up then drop back to temp. I always told myself it was due to the hot water in the block going out and the cooler coming in.

 

[Old77]

Yeah, is say once your tstat is replaced you'll see that go away.

 

[89Suburban]

Yeah, is say once your tstat is replaced you'll see that go away.

 

[HotRodPC]

Does sound like a lazy Tstat. Now it is common to see the temp go up to 195, then fall back to below 100, then back to 195. That is because the Tstat has the water blocked off in the radiator that is cold, so until your Tstat pops off maybe 3 times and all the water has now circuated thru the engine at least once, that may stabilize. That is normal, especially if you have a biggo radiator. My 454 truck does that. It'll get to 180, then drop to about 120, then back to 180, then drop to about 140, then to 180. After that, it pretty much stays between 180-190 depending on the driving. In this bitter cold, it stays between 170-180 now that I have the new Tstat installed. And the heater is working great now too.

 

[89Suburban]

Does sound like a lazy Tstat. Now it is common to see the temp go up to 195, then fall back to below 100, then back to 195. That is because the Tstat has the water blocked off in the radiator that is cold, so until your Tstat pops off maybe 3 times and all the water has now circuated thru the engine at least once, that may stabilize. That is normal, especially if you have a biggo radiator. My 454 truck does that. It'll get to 180, then drop to about 120, then back to 180, then drop to about 140, then to 180. After that, it pretty much stays between 180-190 depending on the driving. In this bitter cold, it stays between 170-180 now that I have the new Tstat installed. And the heater is working great now too.

Are you running the 195* thermostat? Shouldn't it hold that temp?

 

[Old77]

It won't necessarily "hold" the temp but when your temp gets up to around 205 or so it'll open up and cool it down to 193 or so then close back up a little. Is that what you're asking?

 

[HotRodPC]

Are you running the 195* thermostat? Shouldn't it hold that temp?

Nope, in my non computer vehicles I run 180. Computer vehicles I run 195.

 

[89Suburban]

Any thoughts as to why the heater hose from the manifold to the heater core is 5/8", and the hose from the core to the radiator is 3/4"?

 

[Irishman999]

All I could figure is it keeps the hot steamy coolant from flowing out of the heater core so fast. The smaller hose is the exit right?

 

[89Suburban]

All I could figure is it keeps the hot steamy coolant from flowing out of the heater core so fast. The smaller hose is the exit right?

No.