Could a small leak in the heater core introduce air bubbles into the cooling system?

[Jimbo]

Could a small leak in the heater core introduce air bubbles into the cooling system?

I have had all the symptoms of a pinhole leak in the heater core for the last 6 months or so (fogging of driver side of windshield, slight smell of coolant when heater is on...) but have been trying to put off the repair because of the cost. However, in the last couple of days my car has started to run way hotter than normal(temp needle almost to red) and my mechanic who has the car now thinks it is a problem with the electric aux cooling fan. He thinks it is possible the fan is not working because air bubbles in the system are causing the aux fan switch to not engage, he is not a BMW tech so I was curious if anyone else had had this problem.

Any ideas are greatly appreciated.

[632 Regal]

if the heatercore is leaking you might have lost enough coolant to get an air pocket in the engine. I doubt that you will get air in the system from a hole in the core though.

[homer+vat]

Have the radiator re-cored. If it is bad enough to have a hole then it's possible it could also be blocked and not cooling enough water. I had the same problem on a Honda Prelude, it ran hot at speeds up to 60 MPH but boiled up at higher speeds. Everyone said the head had gone, but turned out to just need a new rad.

Andy

[JonE]

The electric aux. fan in front of the radiator will come on with the AC, you can see and hear it spinning from under the front of the bumper, if it's working. It will also come on (with the AC off) when temp. guage is a bit higher than about 3/4, which you don't want to have happen.
The engine fan (the one behind the radiator) uses a viscous clutch that pulls air through the radiator if it is working properly. When not working properly and the engine is fully warmed up, it will not be blowing alot of air around under the hood and might even free-wheel when a warm engine is shut off (it will continue to spin for awhile).
The heater core leak could also contribute to the problem if there is, like Jeff said, an air pocket in the coolant system. You might want to try bleeding the system, but also check the engine fan operation to make sure it is blowing air fairly vigorously under the hood.
Lots of possibilities, so go at em one step at a time.