'93 BMW 316i overheating in idle

[CAFB 04-12]

I have a British spec 1993 BMW 316i that is overheating in idle. There are a couple symptoms: At normal driving speeds the temp stays in the normal range but in idle or in slow traffic it starts to heat up. I get no hot air through the cabin heater either (neither of the air hoses into our out of the heating core get warm). It seems like these may be related problems. I don't know a lot about coolant systems, but from what I've read on this forum there are a couple things to troubleshoot:

1. Bleed the system. I watched a mechanic do this last winter when my heater wouldn't work, but I'm not 100% sure how to do it myself.

2. Check the water pump. I let the car warm up and the coolant return line (into the radiator) gets hot, so it seems like it is pumping coolant to the engine block.

3. Thermostat. I'm not sure where it's located on the '93 316i or I'd replace it to see if that's the problem.

Mostly I just want to have some knowledge of the system when I take it to the mechanic, so I know what I'm talking about. Anything else I can try at home?

[Bear]

If you do not have a bleed air problem and your car has the viscous de-clutching fan (not the electric) my ETK says you do, I would look at the fan clutch. I have solved cooling at idle on both a '90 325ic and '88 750il by replacing the fan clutch.

[shomidas]

I have a 95 316i saloon with automatic transmission and had a similar problem. It seems almost certainly to be the viscous fan clutch. Turning the fan by hand when engine is stopped and still warm can give some indication if the fan feels free. These fans last about 3 years from what I have heard and read. Anyway changing the fan clutch solved the problem in my case. I have now got a machine shop to fabricate a fixed fan holder instead of the clutch and will try it the next time it happens. It could be a sticky thermostat which sticks above a certain temperature or it could be the radiator or the water pump. So I would start with the fan clutch and work through.

[CAFB 04-12]

Thanks for the tips. When the car is running the fan is turning. Is this clutch something that makes it turn faster at hotter temps? Or is there a second fan closer to the radiator that I'm missing?

[Bear]

The clutch allows the fan to grip the water pump shaft and turn at the water pump speed, if the clutch fails, the fan just free wheels and is not doing its' job. One old method (do not know how good) was to take a rolled up news paprer and with the engine running try and stop the fan blades from rotating (watch your hands). The story went if the fan blades tried to shred the news paper, the fan was good. I have replaced the fan clutch on both a '90 325 and '88 750 for overheating at idle and in both cases the problem was solved.

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check fans, relays, coolant and thermostat (most important)

[davielad]

I am having the exact same problem and I have the same car. two days ago i bought a 316i compact 1600 model. Temp was going all the way up to the red. I changed the thermostat thinking it was that and problem is still the same. I did the clutch fan trick and it has no force atall so I have bought a new clutch fan to be fitted , im hoping this will sort my problem.