Hi All,

I have a question. I have a 190 degree thermostat and live in FL.

Around town car runs between 190 and 200 degrees. Saturday took the car on the highway. At 70 mph, temp went up to 210 and continued to rise. Backed off and kept it at 60 mph and it stayed at 210 degrees. When I started to push back up, I started to go over 210 again.

I have no idea what "normal" should be. Honestly, I do not know what overheating would be? Always had idiot light, never a mechanical gauge.

I was expecting the car to stay below 200.

Car is a 455 W30 / auto trans w quadrajet.

Any insights.

Thanks....TP

 

I'd put a 180 degree thermostat in there. What is your timing set to? When was the last time your checked your radiator or flushed it. How old is your antifreeze?

 

I do have a 180 degree thermostat,

Uh oh - how does timing relate? I have had timing issues since I put the engine back in the car. I pretty much have to set the timing by ear. I advanced until the puppy starting pinging and then backed off a hair.

I still have pretty major issues at idle, but the car runs a lot better.

 

You stated above you have a 190 deg thermostat.

What issues do you have at idle, and what is your setup?

 

It sounds like you've got an inadequate cooling system component somewhere.
Could be the thermostat, could be the radiator, could be the water pump, could be that the block is full of rusty crud.
Since the problem only happens at high speeds, your fan, fan clutch, and fan shroud are minimally involved.

I've had problems like this before, myself - without an obvious culprit, they can be a bear to diagnose.

As for your thermostat - at 200° a 190° should be fully open.
So should a 180°.
Same for a 195° or 160°.
For this reason, I would not mess around swapping different thermostats. Under the temperature conditions you describe, ANY thermostat should be behaving the same way.

Since it's one of the easiest and cheapest cooling system parts to fix, I would check the thermostat first.
Take it out and put it in a pot of water with a candy thermometer, turn on the heat, and watch the thermostat and the gauge - at around 180-185° it should start to open, and it should be fully open by 190°.

Once you've ruled out the easy part, the fun begins.

- Eric