E36 Overheating - United Bimmer Community

**Dave7162** · 11-07-2010, 05:26 AM

Hi everyone...this is my first post so be gentle with me. My problem is with my E36 1.6i saloon overheating. It only overheats in slow traffic or when stopped, when on the move it's fine. I have checked for leaks and found nothing obvious. I don't have any white smoke from the back and performance seems normal. Also the heater only blows warm air when on the move. There has been no work done on the cooling system during the last year, so I can't blame faulty workmanship. One last thing, I can turn the fan blades quite easily by hand...is this normal? Any tips would be appreciated.

**Manolito** · 11-07-2010, 09:18 PM

I am not at all familiar with the 1.6, so this is generic advice. The two symptoms you describe don't necessarily 'fit' together to point to a single problem.

You were right to check the fan. A car that heats up at low road speed and cools down at highway speed most likely has a fan problem. If the water in the radiator is hot, the fan should be pretty stiff. When it is cold, it should spin fairly freely. Examine the fan clutch to see if it appears to have lost its fluid (i.e. it looks oily). If so, replace it. You will need to make a tool to hold the fan pulley still while you loosen the fan. It is left-handed thread.

Do you have an electric fan as well? Do you have a temperature sensor screwed in to the side of your radiator? If so, pull the plug off the temperature sensor and with the key on, see if you can turn the fan on by shorting the outside wire to the brown ground wire in the plug. One outside wire should get you low fan speed and the other should get you high fan speed. If you can hear the relay click but the fan does not come on, it could be the relay contacts, the resistor on the fan, or the fan. Relay is first suspect. Electric fan is expensive so hope it is not that. If the mechanical fan works, you should be able to live without the electric fan.

A heater that blows warm only when the car is moving indicates that it is getting water though the heater core only when the water pump is spinning fast. This could mean you are low on water, or someone has plugged the heater core up with bad water deposits or radiator stop-leak. Another possibility, which might also answer the first problem, is that the impellers on the water pump have rusted away, or, if they are plastic, gotten brittle and broken off. How many years/km on that water pump? Water pumps generally last about 10 years or 200k km whichever comes first. Some plastic impeller pumps don't last that long.

**al22** · 02-28-2012, 02:53 PM

if you dont have an electric check the viscose cupplin

DEATH2000 · 02-28-2012, 07:37 PM

I'm sorry, check WHAT? Please explain.

**al22** · 02-29-2012, 04:38 PM

there is a cupplin behind the fan which lets your fan spin but its oil filled and after meny years of use they spin slower than they are ment so the rad dose not pull air through to keep the water cool

DEATH2000 · 02-29-2012, 05:04 PM

It's coupling. Not "cupplin". The fluid in a viscous cupplig is normally silicone based. When it wears out it allows the fan to spin freely, not nessecarily slower.

**al22** · 03-02-2012, 05:59 AM

I would thought the same as you but some one pointed this out to me so I changed it because I had tried everything else and it did work as you so rightly point out they are silicone based that was my mistake but I was told that if the silicone had gone thin in the coupling it courses less resistance so the fan will not spin at the same speed as the engine