Overheating Problem When Idle

[MichaelGFunkEra]

Hi,
As the subject says, my car overheats when idle. It usually goes down to the regular running temperature once I start driving. That is until I hit a red light, stop sign, traffic, etc. I have just recently (within past 2 months) had a new thermostat installed and antifreeze checked. I have also noticed recently that when the car is in park or neutral that it starts to rev itself up. The tachometer will go to about 3000-3500rpm and then back down to the regular idle of around 1000rpm, and then the cycle will repeat. Each cycle of revving lasts about 4-5 seconds. Any help on these problems, or this collective problem is appreciated. And by the way, anyone know what it would cost approximately to have these problems fixed? Thanks again.

[mpumas]

Does the fan turn on when it gets hot? :Your problem with heat sounds like a water pump that is not moving the water at idle.

I don't know about the engine reving up but when it does does the temp go down?

[blacknight]

Well, there could be a couple of reasons. It could be the water pump, Or the thermastat could be acting up. Worst case is that you have a shot head gasket which could possible be the reason. Once the car is sitting the temp gauge will go up. But once the car is moving (over 25mph) it'll go back to normal. A good sign of that is if the car is overheating and you see white smoke from the exhaust.

Also, maybe the upper/lower radiator hose is faulty/clogged. Also, if you get a chance blow out the radiator. That definitely helps. Get air hose. And blow air into the front of the radiator to remove all the debris that in there. You'll be suprised how many little bugs and stuff can accumulate over time.

Good Luck

[jbuffethed]

my wifescavalier did this overheating thing at lights. This all started when the car blew a head gasket, they pulled the lower radiator hose and now coolant came out, so that got replaced, new thermistat and water pump. still didnt fix it, turns out the relay for the fan had melted. Just replaced that and it fixed it.

[jeffcoslacker]

Sounds very much like your primary fan isn't working. If the water pump, thermostat or blockage were the problem, the motor would heat up faster when moving. More work, more speed = more heat. If the coolant isn't moving, it can't get rid of that heat and boils over quickly. Your problem is lack of airflow through the radiator while stopped. With the other symptom of the unstable idle, I'd wonder if the coolant isn't low, and surging over the temp sensor, making it unsure of whether to idle at cold or warm strategy, and causing the fan sensor to not sense the coolant temp. By running the A/C switch on, it should make the aux fan run, and that should keep it cool when not moving. If so, the primary fan is your problem. I think I'd check the coolant level first, with the motor running and warm, not hot, then check the fuse and relay for the primary fan. If that all checks out, look for a spent fan motor or sensor glitch.