MechanicGuys - Little Help? (1 Viewer)

[MikeIke]

Problem just started yesterday. When sitting at idle the heater blows cold air and the temperature gauge starts to climb. When I get going again, at a good speed (around 45) the air blows warm again and temperature drops. What would cause this?

My coolant is full. I haven't done anything to the coolant system lately that would make me think it needs to be bled but I'm gonna do that tonight just in case.

If it were a thermostat problem, would the air blow hot at all? I'm thinking it wouldn't buy I'm probably wrong. I actually have a spare thermostat so I think I'll change that this weekend just in case.

Any other tips or suggestions on things to check? It's a 2002 Subaru WRX with 120k miles. 8k miles ago I had all fluids replaced, new radiator installed, and timing chain replaced.

 

[snellman]

Does not sound like a thermostat problem. It sounds like you may have an air pocket in your cooling system. Some models are known for this issue. Not sure about subaru because I primarily work with GM products. If you had your coolant and radiator replaced, the system may not have gotten completely bled. You said the coolant level is full, but is it full in the radiator and the overflow?

Other possible problem could possibly be a water pump or head gasket problem (hopefully not), but the Temp guage rising at idle along with the cool air has me wondering a bit.

 

[MikeIke]

Thanks for the reply. Both the radiator and overflow tank are full.

I did have to replace a hose a couple months ago and bled the system back then. I haven't had had any problems since then until yesterday. I'm going to bleed it again tonight just to see if that will fix it. I'm just wondering what else it could be.

Water pump was my next guess, I just don't know if I could replace that myself. I'm a tinkerer not a mechanic.

 

[MikeIke]

If I turn on the AC, are the radiator fans supposed to kick on and stay on? Because what's happening is, with a cold engine, the fans turn on when I turn AC on but then stop after about 20 seconds.

 

[SWC]

brohan i am guessing water pump or head gasket but if the mechanic brothers say it is an airpocket i would give bleeding that sucker a shot because it is going to be a lot cheaper than a pump or a gasket sorry to hear it man and i hope you can get it fixed lickety split take that to the bank bromigo

 

[Bucks]

So the coolant is only flowing at high rpms. Sounds like the water pump isn't working at low rpm's. Could the belt be loose causing it to slip.

Sure you have coolant in there and not ice?

 

[SWC]

or your water pumps fins are shot or it and this is really a technical term just went to hell that is sort of what i was thinking and i am also watching the bucks play the nets right now so bam that right there is some kismet going on take that to the bank buckhan

 

[sbonomo]

Honestly, start with the cheapest part first. This absolutely could be a malfunctioning thermostat. worst case it cost you 30 minutes and 5 bucks to replace. If that does not do the trick my next guess would be the water pump as well. Replacing is probably not as hard as you think. Just out of curiostiy have you ever flushed the system?

ETA - I had a heating core go out a long time ago in an older truck, but it quit blowing hot air all together. Could possibly have something to do with this, but less likely.

 

[MikeIke]

Just burped the cooling system and there were quite a few air bubbles. Car idled for half an hour without overheating, and the heater was blowing warm. Fingers crossed that all it was, guess I'll find out tomorrow.

Sbonomo, yes the radiator was replaced in January so all be coolant was added.

 

[MikeIke]

Just took a quick trip to the gas station on the corner and temp stated correct, warm air coming from the heater. Hopefully the girl just needed to be burped.

 

[GroveDiesel]

Hope that was it. If not, it definitely could be a bad thermostat. I had the exact same problem and it was just a bad thermostat.

 

[SWC]

good news brohan nothing worse than having car crapola during the holidays take that to the bank

 

[Raider Nation]

Get the Johnson rod replaced.