Overheating in 13*F highway driving! New thermostat. Please help!

[TravisT]

I’m just looking for some quick advice because my parents arrive in town tomorrow and will need to drive this car.

Replaced the thermostat assembly. After that, the car would not warm up properly and temps would bottom out the gauge going downhill on the highway. I figured that I got the thermostat cadywompus in the assembly housing (it’s designed to seal into a domed housing, allowing some movement and self correction with moving fluid).

Yesterday afternoon (3F* outside) I took the radiator hose off and used a screwdriver to slide the thermostat into a more aligned position. A quick test drive proved that it could reach FOT quickly.

This morning (-10F* outside) the temp gauge rose quickly under load, but then dropped quite a bit while coasting downhill for 10 miles. I figured it was just the outside air super cooling it.

Drove on the highway up a long gradient and the temps rose to almost the red. (13F* outside). Pulled over and the fan was on full, the coolant reservoir was not boiling, and the cabin was plenty warm, the radiator hose was pressurized but freezing cold. The air being pulled from the radiator by the fan was cold, and the bottom radiator hose was cold.

Why am I not getting any water through the radiator? Yet, the radiator is pressurized? I released the pressure from the reservoir (It did not boil out) and after that the radiator hose was no longer pressurized, but still cold.

Any suggestions?


Many thanks!!

[dcninja123]

sometimes you will get a bad thermostat... try replacing it with a different one?

[sjonnie]

Replaced the thermostat assembly.
Why? Your description makes it sounds like all your problems are caused by replacing the thermostat but something must have been wrong to prompt you to change it. I assume you have an '01?

[TravisT]

Why? Your description makes it sounds like all your problems are caused by replacing the thermostat but something must have been wrong to prompt you to change it. I assume you have an '01?

2003. Being brand new to volvos the only replacement thermosat I could find in short order wad to replace the entire housing, which included the thermostat.

[dcninja123]

It's quite obvious that he is saying he had an issue, replaced the thermostat, and he is still having the issue and is looking for advice.

[gibbons]

Check the dilution of your antifreeze. If it's not "strong" enough, it can freeze in the radiator, blocking flow, and causing overheating.

[mapper]

Gibbons nailed it. Weak antifreeze mix and the rad will slush and plug up at cold temps causing engine coolant temp to go up. City driving is fine because the motor generates enough heat to keep things moving but on the highway the airflow is too cold. Test it by the following: pull over, shut off car for a min or 2, start up again and drive slow and all will be well. Or just get the coolant checked for proper mix, you can get a little tester at the autoparts store.

I had the exact same issue years ago on my VW after I had fixed a leaking coolant pipe on it. I didn't have the proper antifreeze so I filled with diluted water since it was summer. Forgot about it and all was well until one winter night I started driving up a mountain pass and the car began overheating at roughly 10 degrees F. turned around and drove slow to nearest town and debated what to do, it was late. started car and all was well so I tried the pass again, same thing overheating. Went back to my friends house for the night and took the car to the local VW shop on the assumption my water pump impeller had failed and couldn't keep up with the highway speeds (there was a run of bad impellers at that time). Told the mech to do the whole t-belt and everything while he was in there. He called me later that afternoon and told me my anti-freeze was mostly water. DOH!!! Never felt more stupid in front of mechanic in my life. Quick coolant change and all was well.

[TravisT]

I don't think it's the antifreeze freezing. I flushed it and it has fresh 50/50. I left a bottle out last night and it wasn't frozen, but could have been slushy I guess.

I ended up pulling the housing twice tonight. Once to just verify that everything was where it was supposed to be, and it overheated during the test run.

Then I pulled it off again and drilled 4 1/8" holes in the diaphragm. Now the overheating is gone which is good for safety, but the temps are too low. I drilled the holes because the old thermostat was surrounded by 1mm holes. This new thermostat had none. At least now I have some coolant flowing through the radiator and into the top hose.

I'm going to contact Arizona Autohaus and see if I can get a refund or replacement.

[RockitShip]

Then I pulled it off again and drilled 4 1/8" holes in the diaphragm. Now the overheating is gone

Are you sure the thermostat is facing the correct way?

[mapper]

Sounds like you may have had an air bubble trapped at the t-stat and it needed the proverbial "burb". May have been that simple.

But I'll add, just in case, and for the sake of future readers having a similar problem:

Are you sure you didn't buy pre-mixed anti freeze then dilute it again thus getting 25/75. Wouldn't be the first time a silly mistake was made, at least if it was me anyway. Liquid flowing through the rad could easily cause it to slush at temps where a larger quantity (in a bottle) may not be affected. My overflow tank always looked good. It may be something else but never hurts to consider the obvious simple solution.

[TravisT]

Sounds like you may have had an air bubble trapped at the t-stat and it needed the proverbial "burb". May have been that simple.

Are you sure you didn't buy pre-mixed anti freeze then dilute it again thus getting 25/75. Wouldn't be the first time a silly mistake was made

Nope, straight up 50/50. I bought a bunch of containers.

Interesting about the bubble concept. Coolant should have been flowing through the engine just fine, just not past the thermostat, causing the radiator to get backed up. I think I'll drill one 1mm hole in the next T-Stat I get to mitigate the bubble theory.

Oh, and there is only one way the T stat can fit in there.

[RockitShip]

Boil the thermostats you have used and currently using on the stove in a pot of water to rule out whether or not they're working (they should open/compress). This should at least help you as to whether its the t-stat or something else such as a water pump, etc.

[bfife]

Sounds like you may have had an air bubble trapped at the t-stat and it needed the proverbial "burb". May have been that simple.

But I'll add, just in case, and for the sake of future readers having a similar problem:

Are you sure you didn't buy pre-mixed anti freeze then dilute it again thus getting 25/75. Wouldn't be the first time a silly mistake was made, at least if it was me anyway. Liquid flowing through the rad could easily cause it to slush at temps where a larger quantity (in a bottle) may not be affected. My overflow tank always looked good. It may be something else but never hurts to consider the obvious simple solution.
I'm with mapper on this one. I think you had a air lock. I've seen it on stockers and on full race rigs. gotta get the air out.
Barney