[Differentiall]

I own a 2006 330i 6sp MT with 70k miles on it. In the past week or two this has happened to me twice. I drive the car and it overheats. I pull over, shut the car off and wait for it to cool off. After it cools i continue my driving and have no problems for about a week. Well I drove the car two days ago and it overheated again so I did what I usually do. This morning I overheated once again but this time I noticed my car was blowing ice cold air when the heat was on full blast (the car should have been warmed up. I drove for about 15 minutes). After I pulled over and waited for it to cool down. When I started it up again it blew very hot air as soon as it started.

I've done some research and I've come down to thinking it may either:
1) thermostat problem
2) I have an air pocket somewhere in the cooling system

My water pump works as I did the test for that (by holding down the gas for 10 sec. while the car is off)
Also, I have coolant and there are no leaks in the coolant system. I had this checked because I recently had to put in a new coolant reservoir.

I was wondering if someone would have any more info on this?

[VTECaddict]

Water pump. Sometimes it fails intermittently before it fully goes. If you get the codes scanned you'll most likely see stored codes for the water pump.

[mmmnot]

At 70K I'd do waterpump/thermo regardless - which obviously includes a proper flush.

Don't wait until you need a flatbed - this is the perfect excuse.

[Volasko]

Originally Posted by VTECaddict

Water pump. Sometimes it fails intermittently before it fully goes. If you get the codes scanned you'll most likely see stored codes for the water pump.

Originally Posted by mmmnot

At 70K I'd do waterpump/thermo regardless - which obviously includes a proper flush.

Don't wait until you need a flatbed - this is the perfect excuse.

But he said he confirmed his water pump works......

[mmmnot]

Originally Posted by Volasko

But he said he confirmed his water pump works......

Right, but these are known to flicker in and out before failure. Shadow codes would confirm/deny the assumptions.

Regardless of it's condition, in MY humble opinion, it should be addressed now rather than after failure. I'd rather pay now and prevent failure and avoid a flat bed than keeping the money in my pocket for until it does fail.

Again, just my 2 cents and exactly what I did with my car.

[Differentiall]

thanks guys. I'm bringing it into a BMW dealership to get it checked tomorrow. I'll see what they say. I too would rather pay now than later. I've also heard that it could be a rotting of hoses that could be allowing air into the cooling system? Could that be possible as well?

[rjahl]

Change the water pump for good measure. If it has not already failed you, statistically it will fail in the near future. Look for other causes but the pump is the prime suspect. Check the codes.

It's an easy job if you want to save some$$$$

[matteblue3er]

If you scan the DME, a shadow fault will typically store, indicating a deviation in pump speed.

98% of the time, this fault means the pump is failing. You need a BMW specific scanner to pull this fault.

Another sign to look out for is your radiator fan screaming immediately after startup or shut down.

Btw, the dealer will clear the fault and wait for you to complain again. That's how they do things at a dealer. I suggest you get the pump changed before it requires a tow.

[Three_thirty_I]

At that mileage I would definitely change the water pump, thermostat, any old hoses, and maybe even for good measure, the temperature sensors.

[hassmaschine]

pull the codes first and see if it's failing. I'll bet it is. But I disagree that you'd need to change it just because it has 70k.. lots of them last well beyond that.