im trying to find out if an air pocket in my cooling system is causing my car to heat up while cruising on the highway.

for the past 2 days ive been driving my car 30 miles each way on the highway with speeds varying from 65-80. the car will start to rise in temperature toward the middle marker and sometimes a little above on the temp gauge. this happens toward the end of the trip and sometimes in the middle. i have to turn on my heat to notice a drop in temps. i recently bled the entire coolant system out and replaced my fan switchs. so now the car wont overheat in traffic or long idles but it rises on the highway. my t-stat is only about 2 years old at the most and im not losing coolant.

could this still be another air pocket?

 

try to take out the bubble first. after you changed the fan switches. does the fans come on at all? i would change out the t-stat too. might not be opening up.

 

hmm thats rediculous, so sometimes randomly it heats up like 5-10 degrees warmer? idk what that could be other than try changing your air filter and running some seafoam or doing "the water torture" to clean out crudz

im just taking guesses here

 

yea it is strange.

 

At speed, there should be sufficient air flow thru the radiator to keep things cool. I would check that there is no blockage (like leaves and debris) interupting air flow.
How did you bleed the system; bleeder screw?
I suggest raising the vehicle's front (ramps will do), making the radiator the high point on the system. Starting the car with the nose raised will force any remaining bubbles into the radiator where they can be purged.

Put it up on the ramps (don't let it heat up)
Remove the radiator cap (while cold)
Start Engine
Run until circulation is noted going past the radiator cap neck.
Top off system as needed.
Replace cap
Adjust level in Overflow bottle.

P

 

thanks for the advice. i will do that.

 

Also maybe make sure that your coolant is a 50/50 water/antifreeze mix, or whatever your car's specs are; get the coolant testing doohikey ($2-$3 @ Walmart, I think) and take a sample directly out of your radiator.

 

also, just because ur t-stat is only 2 yrs old doesnt mean it cant be shot...

 

fair point.

 

If you want to test your t-stat, take it out and put it in a pot of water and bring the water to a boil and the t-stat should open, if it doesnt then it is bad.