BMW viscous fan clutch

mkdon05

This ones to all my bmw buddies, my e36 is overheating and im pretty sure that the viscous fan clutch needs to be replaced, Anybody got an idea of how much these cost?
Went to change the thermostat and found that some loo - laa :rolleyes: had removed it befrore i bought it. So im hopin that the water pump doesnt need replacing!!:mad:

Blue850

Is it getting hot just in traffic or on the open road, is it losing coolant?, with the thermostat removed , i'd consider the head gasket

mkdon05

Its only overheating in traffic or when its just ticking over when parked, once its on the open road shes grand, comes right back down to normal, Im thinkin the clutch in the fan is leaking the fluid that thickins, therefor needing a replacement, hopefully its not the head, that would be cha ching:(

MercMad

I got one for an E36 from OTTO, cant recall how much as I got a camshaft and rockers aswell as service kit too !

Check them and GSF car parts, you might get the costs on the web !

greglo23

if it was mine i would throw out the engine driven fan and replace it with an electric fan. engine driven fans are the worst way of cooling your engine as they only turn at slow speed in traffic when the engine needs the most cooling !! admittedly the viscous drive fans are better than the old permanently driven ones but its still a very inefficient way of cooling your engine.

if the engine temp is at normal when on the open road with no stat i would be suspicious. check that the whole rad is getting hot as it sounds like the rad may be semi blocked.

Seth Brundle

The viscous fan clutch needs a 36mm offset spanner turning reverse thread IIRC.

@greglo23 - It's a viscous coupling. The temperature affects the viscosity of the fluid in the coupling, which in turn increases/decreases the drag. The
result is that when the engine is hot, drag is increased and the fan
spins faster. Therefore, in thoery, whilst sitting (for a while) in traffic the fan should spin at its fastest.

franksm

How do you diagnose a failing viscous fan ? Should it be REALLY easy to turn on a cold engine ? That's the way mine is (Merc 2.3) and while it doesn't overheat, it does run slightly hotter than I'd like. Going to change the thermostat, but am wondering about the viscous.

I put electric fans into a Stag a while back, and needed to insert a thermostat/switch into the rubber pipe at the top of the rad. Apart from that, it was an easy job.

Viscous clutches for the Merc are about £122 STG --> which is the same price as a kenlowe fan kit

Seth Brundle

If the car overheats whilst standing then there is a newspaper test - roll up a newspaper and see if it stops the fan when the engine is running. If the fan stops then the clutch is fecked.

greglo23

kbannon i know exactly how a viscous fan works. the fact that it turns at engine speed is my point. at tickover in traffic it turns too slowly to provide effective cooling for a hot engine even though it is a bmw. an electric fan only works when it is necessary. when cruising on the open road it does'nt need to turn as the air is coming through the rad anyway and when stopped in traffic it works at full speed to keep the engine cool.
it is reckoned that a mechanical fan uses up to 8 hp at full revs and also creates a hell of a racket. the old peugeot's used a combination fan which was like a viscous fan but had an electromagnetic clutch which cut in at high temps.
the japanese nailed the problems associated with electric fans by making a very clever failsafe switch design. instead of the european design where when the switch went kaput you had no fan the japanese system used a switch which kept the fan off until the temp rose above a certain point. if the switch broke the fan came on with the ignition and stayed on while the ignition was on. i know i'd much prefer my car to be a bit too cool than a bit too hot. a new switch is also a lot cheaper than a headgasket and all the trimmings.:D

Seth Brundle

I sit in traffic every day (twice a day!). The fan provides effective cooling for my car (523i) as the needle never moves off the centre point when the engine warms up.

Heart_N_Soul

Heya
Same thing happened my E36 last xmas... sitting in traffic and the light in my dash was broken so i didnt see the thing overheating, then there was a bang!!
Turned out the fan wasnt working, blew up the radiator too.
The whole repair cost me 400 but that included the radiator.
I would ring traynors for the parts (048 38891242) they bring them down to dublin twice a week, dont let the garage buy them for ya cos they add on like 300% to the cost price.

Emma

Mr.Diagnostic

greglo23 wrote:

kbannon i know exactly how a viscous fan works. the fact that it turns at engine speed is my point.

Hi,

A viscous coupling does not allow the fan to run at engine speed, ever. There is no lock up.

In brief, the coupling contains 2 chambers. The amount of oil allowed to move from one to the other is controled by a valve which is controled by a bi-metal strip on the front of the unit. This is what sets the speed of the fan relative to the drive speed. Of course a blocked Rad will stop the fan from functioning correctly if the temp at the bi-metal is low.

HTH