96 cavalier running cold at highway speed

[pepa]

We have a 96 Cavalier that runs normal temperature at speeds below 50 mph but will lose temperature at higher speeds, especially if it is cold outside. I know, I know, thermostat right? That was our thought 6 thermostats ago.

We have bled both bleeders. Topped off the coolant. No water in the oil. No leaks or level changes. We are running green coolant (converted professionally from the original orange).

It runs fine in the summer, but without heat in the winter it is a big problem.

If you have a solution you are our hero!

[04_CaV!!]

this might worth looking into. clogged heater core or blower motor.

[public]

I think the engine is getting to the right temp. The heater core is probably full of DexCool crap from when the orange coolant was in there. Try Disconnecting both heater hoses and back-flushing it. If you get good flow you will need to check the baffle door next to the heater core under the dash.

If all of this is okay then you can obstruct 1/2 of the radiator with a piece of cardboard. This is a temoprary fix but you will get heat. Many semi-trucks do this every winter, they just have snap on vinyl covers.

Good Luck.

[deadBird]

I have the same problem. Get your coolant system pressure tested. Anything from a weak water pump or hose to a obstruction in the radiator can be it. Another telling sign is if you have coolant coming out the front right corner of the manifold.

But, in my case, looks like a blown head gasket. Check for white smoke out the exhaust. If even a little, then that's coolant burning off. Head gasket probably.

Your best bet is to probably take it to the shop.

[stalbert]

Problem solved!!!!!!!!!!!!!!!!!!!!!!!
Its the brand of thermostat you are using.
I put two different "motorad" thermostats in my 99. Had the same problem you did. Cold at highway speeds. It turned out not to be a speed problem, but an RPM related problem. If you dont believe me run your engine over 2600 rpm or higher and watch your temp gague go down. Even in first gear.
I bought a thermostat from NAPA and it instantly solved the problem. The spring in the NAPA part is twice as strong, not allowing it to open unless its actually supposed to. The motorad one is jsut to cheap.
Hope this solves your problems as I had huge headaches for a very long time trying to figure this one out.

Peace!

[kirby747]

Originally Posted by stalbert

Problem solved!!!!!!!!!!!!!!!!!!!!!!!
Its the brand of thermostat you are using.
I put two different "motorad" thermostats in my 99. Had the same problem you did. Cold at highway speeds. It turned out not to be a speed problem, but an RPM related problem. If you dont believe me run your engine over 2600 rpm or higher and watch your temp gague go down. Even in first gear.
I bought a thermostat from NAPA and it instantly solved the problem. The spring in the NAPA part is twice as strong, not allowing it to open unless its actually supposed to. The motorad one is jsut to cheap.
Hope this solves your problems as I had huge headaches for a very long time trying to figure this one out.

Peace!

Indeed? I'm having the same prob, put in a new one yesterday,and the old one looks fine, will try one from napa, someone mentioned 2 vent screws i found one on the front where's the other?

[deadBird]

Yep... 6 $hitty duralast thermostats later, I decided to buy a Napa 'stanton' t-stat. Problem 100% fixed.

[kirby747]

Resounding Amen and big thank you to Stalbert, it was that simple.

[|WYG|SS]

Originally Posted by pepa

We have a 96 Cavalier that runs normal temperature at speeds below 50 mph but will lose temperature at higher speeds, especially if it is cold outside. I know, I know, thermostat right? That was our thought 6 thermostats ago.

We have bled both bleeders. Topped off the coolant. No water in the oil. No leaks or level changes. We are running green coolant (converted professionally from the original orange).

It runs fine in the summer, but without heat in the winter it is a big problem.

If you have a solution you are our hero!

Yeah i would go with a new NAPA temp sensor

[Doug56]

I had the same problem on the same year.... the NAPA Tstat Did the trick ....Murray's Auto now offers the Better Tstat ( STANT)