Tell me more ×
Motor Vehicle Maintenance & Repair Stack Exchange is a question and answer site for mechanics and DIY enthusiast owners of cars, trucks, and motorcycles. It's 100% free, no registration required.
up vote 1 down vote favorite

Been noticing lately that my heater stopped working and temp climbs to red. Came to find out that I had no coolant in engine.

Filled it up. Problem is.. it still happens.

Now, radiator full, Heater works fine, but if I drive it for a while, temp climbs and heater stops working. Took it in. Mechanic said coolant pump was leaking. replaced it, and temp sensor.

still happens!

Here is how I can reproduce problem: Drive with high RPMs for about 15-20 minutes. I put it in Low 3, and got on the highway for about 10 minutes. This kept the RPM gauge up to about 4 or 5. temp gauge climbs rapidly once it decides to start.

I drove home after that point never letting the rpm gauge go higher than 1 and a half. (if I did, temp would rise rapidly). coasting in neutral makes it go down. The heater being on has no effect, however, once the temp gauge climbs rapidly, all heat from heater vanishes.

The heater starts working again if the temp goes down (meaning I lowered rpms long enough to let things cool down) when I got home I arranged it that I got back in the driveway with the temp gauge almost in the red. I then put the car in neutral and raced the engine, keeping the RPMs up to 5 for 2 minutes. It had no effect (temp did not climb) I let the engine cool down a little and tried again in Neutral. no go. unable to make temp climb while parked.

share|improve this question
Which engine does your Subaru have? The 2.5L? What mileage is on the engine? – Timo Geusch Mar 28 '12 at 17:29
Did the mechanic replace the thermostat as well? Was it bled properly after all of those items were replaced? – Dude318is Mar 28 '12 at 23:06

3 Answers

up vote 1 down vote

Sounds like either air in the cooling system or a bad thermostat (although it'd be a weird failure mode for the thermostat). Strange that you can't reproduce it when the car's parked, though. How are your motor mounts? I'm just wondering if there could be a problem with one of them that allows the motor to move more than it should under load. This could stretch or kink some of the coolant lines (possibly), which might explain why your interior heat goes away too. Maybe take a look at any coolant lines you can identify and see if they show signs of creasing or twisting.

share|improve this answer
It would make sense why it would not happen while the car is in park. There is a difference when the engine is under load, for one, it heats up more. (my reason for driving in L3). – KevinDeus Mar 30 '12 at 17:36
up vote 0 down vote

It sounds like a bad head gasket if everything else is in working order. Hot gases are introduced into the cooling system under load(hence why it goes down when you let off).

share|improve this answer
up vote 0 down vote accepted

We wound up swapping out the radiator, and that solved it.

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.