Overheating

[theEZV]

Car starts to overheat every now and again. Temp gauge goes up and then back down, sometimes a little, sometimes all the way to the top. I've changed the fan relay, thermostat, and coolant temp sensor. I was sure it was the T-stat going bad. Apparently not. Any ideas as to WTF is going on?

 

[Bowman]

Faulty radiator cap, clogged radiator core, low oil level, air pockets in cooling system, possibly water pump acting up?

 

[theEZV]

Its never leaked a drop of oil or coolant. Has 75k. A little early for rad/water pump issues I would hope.

 

[tweety2300]

Head gasket

 

[Bowman]

I would start with probably the cheapest fix. I've heard of the gaskets going bad on the radiator cap causing issues with the pressure in the cooling system, without actually noticing any loss of coolant.. I believe autozone will test your cap for free..

http://www.ehow.com/how_5911371_test-radiator-cap.html

 

[theEZV]

I guess I'll go ahead and change the cap, its cheap enough.

No steam from the engine even when getting warm/hot, no smoke from the exhaust, no boiling coolant. Coolant level in reservoir is the same as always.

Is there something that can be causing the fan to falter every now and again (not come on)? Fuse?

 

[Bowman]

Are you noticing your fan coming on as the temperature gauge rises? What about your fan blades? Any cracks or broken pieces? A guys car we were diagnosing once for overheating had a cracked fan blade that fixed the issue once replaced as well.

 

[BOOSTR]

It's got to be the fans not coming on even though you changed the relay. Check the wiring with a voltmeter. Headgasket you would see coolant coming out from the block when temp is right. And the coolant would shoot out of the radiator if you have the cap off when the temp is up. But if you have never changed your cap, by all means do it. I'm on my 3rd one with 94,848 miles. New radiator though.

 

[theEZV]

Could it be the fan motor going bad? The fan itself is in good shape. A new fan motor is only $35 from RockAuto. What else can I change? Fuse?

 

[destineal]

Have u seen the fans coming on?

 

[theEZV]

I have caught the car starting to overheat and the fan wasnt coming on, this happened twice. The fan does come on like 99% of the time. Its weird. I also caught the car starting to overheat a bit at highway speeds as well a couple of times.

 

[Spiced MSP]

let the car idle for a while with the radiator cap off and watch for bubbles. Any time I have had fluctuating temps, it was due to air pockets.

 

[theEZV]

I doubt air pockets have anything to do with it. There was no reason for air pockets to be in the system when this whole thing started, everything was original. I have done this "burping" thing a bunch of times. When the car idles with the cap off for a few minutes, eventually little drops of coolant start shooting out.

 

[StealthWyvern]

Any lose of coolant? I didnt see any mention of it.

 

[destineal]

hmm....everything original on a 10 yr old car.

 

[theEZV]

Its never lost a drop of coolant or oil. I meant the hoses were original, the coolant was original, etc (as far as I know, bought the car with 36k).

 

[theEZV]

My dad's been driving the car short distances over the past 2 weeks, didnt overheat once.

I drove it for the first time in a while today. Let it itdle for a while in my driveway and eventually it started to overheat - the fan only came on after the car already started to overheat. Swiched out the cooling fan fuse with the AC fan fuse and went for a drive. Started to overheat again slightly.

An interesting thing is, when turning the fan on manually (turning on the heater), the fan comes on every time right away.

Not sure where to go from here.