Car is overheating

[MattE30]

My car is overheating. I just got back from college, took it for a drive, and noticed that the needle got up to the red until I cranked the heat and kept it at low rpms.

I flushed the system and it is doing the same thing. What are some things I should check?

[bichmgnt]

My first two impulses were replace the thermostat and the fan clutch. But it low rpms brought it back down to normal temp it isn't likely either of those. And if your heater is working then you probably don't have an air blockage keeping the coolant from moving in the engine. Did you do the flush before noticing the problem? You might need to do a better bleeding of the system anyway.

Plus it never hurts to change the thermostat and check the fan clutch. The one trick I heard was the newpaper test - take a rolled up newspaper or magazine and stick it into the fan blades when it is hot and if you can easily stop the fan you need a new clutch. On one of my cars I can stop it with a finger. That one is about to be replaced.

Good luck. I'm still going through coolant loss issues on the other car after replacing all my water related parts including radiator (because it broke), waterpump and all the hoses. Found a leaking sensor gasket and fixed it this morning so we'll see if that was the issue.

Steve

[MattE30]

Well, I bled the system again until no air came out of the thermostat screw.

The overflow reservoir was empty, so I refilled it. I think this was because I just filled the reservoir and didn't get the engine hot enough to get the coolant circulating before I started bleeding.

Anyway, I ran it until the temp gauge got past the midway mark. The fan did not start turning even when it passed this point. I couldn't even try the newspaper test, so could the fan clutch be shot?

The water pump was replaced this winter, so that should be good. The radiator is only a couple years old.

[bichmgnt]

The big plastic fan on the engine side of the radiator doesn't turn at all? Is the belt there? It should be between the crank the alternator and the water pump. If it is there and working that fan should be turning regardless of the temp. If it isn't the fan clutch is really bad and needs to be replaced ($50-60) I think you can do it without removing the radiator. Put a 32mm wrench on the nut that holds the fan assembly on and give it a good sharp whack in the wrong direction. By that I mean it is a reverse thread and comes off in the direction opposite of what you would normally think. The clutch is held to the fan with 4 allen head bolts. That should fix your problem with the car sitting still. If it still when on the highway that is a different problem. That would either be a thermostat or bleeding or the waterpump.

Bleeding from that bleed screw until no air comes out isn't always effective. I know because I had that problem over the weekend. Sometimes you need to pull off hoses and fill through them to get the engine completely full. But if you have heat you did better than me. My heater ran cold until it was fully bled.

Good luck.

Steve

[MattE30]

Why is my coolant expansion tank nearly empty after driving my car?

[bichmgnt]

If your fan isn't turning your water pump may not be turning. If your water pump isn't turning you could be boiling the water out of the radiator. But if you're getting heat out of the heater your pump should be working.

Check your hoses and fittings. You may have a leak. It could also be a freeze plug leaking or your head gasket. Make sure you engine oil looks okay. Look at the sensors on your engine and on the radiator. Also look at the inlets on the radiator. One was cracked on mine.

Again, if the plastic fan isn't turning your car will overheat when it is sitting still and will be okay while moving. You need to fix that.

Steve

[MattE30]

Thanks man, you've been lots of help.

The water pump was replaced over the winter and since I am getting heat, that shouldn't be a problem.

It is only overheating while sitting still, and even then, not by too much. I am pretty much good to go while driving. The fact that the expansion tank has less coolant in it is starting to piss me off.

I guess I'll take a look at the fan and figure out if I should buy a new fan clutch.

By the way, anyone know what discount BMW dealer employees get, as I am working there for a summer job?

[bichmgnt]

...anyone know what discount BMW dealer employees get...?

Ummm... Five Finger?

:twisted:

Steve

[gurpreet]

just curious...

what're the chances you'd have to install a thermostatic bypass valve in the engine compartment and maybe a new design radiator cap to control the pressure and provide greater coolant overflow in case of overheating?

[DarkWing6]

By the way, anyone know what discount BMW dealer employees get, as I am working there for a summer job?

Become friends with the mechanics and then have them help or do it for cheap on the side. I work at a VW dealer and I have gotten free help on a rear wheel bearing and a bunch of other stuff too. Most techs are cool about doing stuff like that.