Car: 2001 Subaru Forester S Modifications: None Problem Description: 1 - It started when the weather got colder, but when I turn the dial on my climate control knob to the hottest setting, it takes about 30 minutes to get hot, then stays hot for about 20 seconds, and then blows extra cold air. I've tried messing with the knobs and seeing if changing them did anything, nothing did. Also, the engine temperature gauge goes waaaay past the red line, which concerns me. The engine doesn't sound, smell, or feel like it's that hot, but the gauge says it is. Recent Modifications/Maintenance: Oil change, but I changed it after this problem started. Can anyone help? I don't want anything bad going on with this car, I treat it almost like a baby, trying to sell it to get into the Lexus SC community...
Try covering half or more of your radiator with cardboard. You're driving too fast. If that doesn't work, replace t-stat with OEM.
The thermostat keeps the coolant in the engine until it reaches a certain temperature. At that point it'll open and allow the coolant to run through the radiator, thus cooling the coolant. A temp. sensor/sender will send a signal to your temp. gauge in the car. Pretty much unrelated. I'd suggest changing your thermostat like recommended. It's a really cheap fix and fairly easy to do. Plus, you'll essentially be flushing your coolant in the process, which I never a bad thing. And on top of all of that, you'll get a chance to burp your coolant system of any possible air bubbles that might be messing with your heater core.
Is it a stock radiator? Had alot of problems with my alum aftermarket in the winter. If I didn't cover at least half of it car took forever to warm up and would not hold a normal temp.
First thing's first, if the temp gauge gets anywhere near the "H", shut the car off. You have an engine prone to head gasket failure, which is likely what you are experiencing, and overheating it leads to warped heads and other damage. I think everyone here is assuming your temp gauge is wrong....I would be very wary of that assumption! Hook up a code reader and see what temp the ECU is reading to verify one way or the other. It's possible you have a failed temp sensor, and the engine isn't actually getting hot, but I doubt it. Hot engine, but no flow through the heater core. I bet your radiator is cool to the touch. Sounds like your coolant isn't circulating. And the only likely scenario for that is air in the system causing the pump to cavitate. The burst of heat tells me there's warmth to be had, but it's just not getting through the core (confirming that the temp gauge is likely correct) If you've had the cooling system drained for some reason recently, you might get away with just burping the air out. But if not, pretty much the only source for air is through a leaking head gasket. The system is likely pressurized (squeeze the radiator hoses, it will feel very different from when it's cold) with air from the combustion chamber. Do a chemical test for combustion gases in the coolant, the tool can be rented for free (refundable deposit), and the fluid isn't expensive. It is necessary to drain some of the coolant, so you will have to replace that. But we're probably talking about less than $20 to get a definitive answer. 99.99% of thermostat failures open too early, causing too much circulation through the radiator, and therefore the engine does not come up to temperature. This will cause weak heat, but the temp gauge will barely move off "C" (and you would not get a burst of good heat).
Thank you guys so much for the in depth information. I'm at work right now, but I'll stop by my grandpa's to use his tools and do all of the recommendations you guys gave me.
