Viscous fan question

Mon Oct 30, 2006 7:28 am

Hi, can someone enlight me on viscous clutches..?
My 320i coolant was under great pressure when stopping in traffic after a drive. I changed the radiator cap as to make sure it is not the 1.2 bar valve inside it dead after 21 years - it changed nothing so I went for the viscous fan clutch.
Every time I give a full throtle I thought it should turn a lot faster...but this is not the case, especially when the engine is hot...
The only time I hear it really blowing is when starting the engine..
How it should be..?

Mon Oct 30, 2006 7:53 am

The hotter it gets the faster it should spin...

I did see a comment the other day saying that the clutch should be stored vertically, maybe yours wasn't....

Mon Oct 30, 2006 7:59 am

what they said is that while new (in the store) it should be store horizontaly...there was even an 'UP' arrow on the SACHS box the horizontal way to be kept...Once mixed the silicone substance inside, then it should be vertically stored...

Mon Oct 30, 2006 8:13 am

While the engine is hot try and stop the fan with a rolled up newspaper, this will tell you if its doing its job.

Dont think you can go wrong with a new fan clutch though

Mon Oct 30, 2006 8:55 am

You're all telling him to change the viscous coupling - but the OP doesn't mention overheating - as indicated by the temp gauge.
The only complaint was of "excess pressure". If the original "recall" pressure cap has been replaced by the improved one, than this is unlikely to happen.
What gives you the impression that the cooling system is over pressurised?

Mon Oct 30, 2006 9:44 am

Brian - how can I tell if my cap was replaced from the recall? Datestamp?

apologies for semi-hijack, 6inline

Mon Oct 30, 2006 9:51 am

When stuck at traffic after a drive ONLY the temperature gauge would go slighytly after the middle (it never did that since I own the car) It would do it even after the new original BMW radiator cap...When stuck all the time in traffic - no overheating problem..
I know it says 1.2 bar on it and it is supposed to get the pressure out but when opening the plastic tank i am expecting a slight 'psst' and what I get is a coolant all over it.
I think that the fan is not cooling it enough which will create the overpressure. Once on the motorway - no problems - the temperature gauge never gets to the middle even when speeding..

Mon Oct 30, 2006 9:55 am

orangecurry wrote:Brian - how can I tell if my cap was replaced from the recall? Datestamp?

apologies for semi-hijack, 6inline

I asked the dealer, he said that there were no outstanding recalls on my car, so I gave him Ãƒ”šÃ‚£6 and he sold me a new cap. I've no idea if it was necessary but it gave me some piece of mind!

Edit: I'd trust most E30 temp gauges as far as I could throw John Prescott.

Mon Oct 30, 2006 10:15 am

Just to make sure I get myself understood...I already changed the Viscous coupling and my first post was about the new one...Should the fan make that specific blowing noise (when cold) every time I give a throttle...because it doesn't seem to do this when hot...

Mon Oct 30, 2006 2:00 pm

Hi there ... my viscous (or at least I think it's the viscous) makes a bit of noise on startup. Annoying whistling noise that disappears after a minute.

Mon Oct 30, 2006 2:13 pm

I may be still drunk from last night but doesnt a viscous fan stop when you get to a certain speed as the air is enough to cool the rad? so you only notice it when stopped?

Mon Oct 30, 2006 3:42 pm

The viscous spins constantly, once it gets to a certain temp, it should lock and you then hear a whooshing noise, thats exactly what mine does, however, wifeys one, you can hear the viscous lock as soon as you start up the car for some reason, leave it on idle all day long but you will not hear the viscous lock and whoosh when hot??

Mon Oct 30, 2006 4:53 pm

ok, I think I have an element of an answer here thanks to a friemd of mine:

''Typically, a bi-metallic element on the front of the viscous drive senses the temperature of air passing through the radiator and operates a valve to control the silicone transfer fluid, thus effecting fan engagement and disengagement. The fan drive is not controlled directly by engine temperature but indirectly by sensing the temperature of cooling air passing through the radiator.''
thanks everyone for helping..

Mon Oct 30, 2006 11:39 pm

orangecurry wrote:Brian - how can I tell if my cap was replaced from the recall? Datestamp?

apologies for semi-hijack, 6inline

All the new type that I've obtained from my local dealer have had a yellow disc on the bottom, but, following a thread a while back on the subject, there appears to be another version around which is all black but has certain numbers on it. Can't remember the details.
If you give the dealer your VIN, they can tell you if it's been replaced, and, if not, should replace it for you FOC.
Of course there's no guarantee that, if it has been replaced, it's still the replacement on the car

Mon Oct 30, 2006 11:42 pm

6inline wrote:ok, I think I have an element of an answer here thanks to a friemd of mine:

''Typically, a bi-metallic element on the front of the viscous drive senses the temperature of air passing through the radiator and operates a valve to control the silicone transfer fluid, thus effecting fan engagement and disengagement. The fan drive is not controlled directly by engine temperature but indirectly by sensing the temperature of cooling air passing through the radiator.''
thanks everyone for helping..

I don't think there is anything wrong with your car at all. (In the cooling department at least).

Mon Oct 30, 2006 11:48 pm

Morat wrote:
Edit: I'd trust most E30 temp gauges as far as I could throw John Prescott.

E30 temp gauges are usually very accurate, as long as the nut on the back of the gauge is tight.
Don't forget, the scale is not linear. The centre section is expanded and only covers a few degrees, so ANYWHERE in the middle section, as long as it's away from both the blue and the red is perfectly OK and normal.

Tue Oct 31, 2006 6:32 am

Don't forget, the scale is not linear. The centre section is expanded and only covers a few degrees, so ANYWHERE in the middle section, as long as it's away from both the blue and the red is perfectly OK and normal.

That is good to know, thanks Brian.

With the new viscous coupling now everything is back to normal - I did a test drive. The original BMW one is 21 years old

and undoubtfully needed some rest

Tue Oct 31, 2006 9:55 am

well mate I hope you got yours sorted becasue mines a bloody nightmare

its an 86 tech1 325 sport. One day after a decent motorway haul the coolant light came on and the temp gauge hit red, I pulled up and the expansion tank was empty, so filled it up and tip toed to destination, tiptoed home later at no more than 50 and lost 3 litres

mechanic replaced the viscous and it was a bit better, but would boil over within 15 miles, losing litres of fluid. I changed the thermostat and the cap fearing it might be weak under pressure, but no real improvement. So mechanic took it in, new water pump timing belt and tensioner whoslt at it. And its a great deal better, but still losing a litre of fluid and the temp needlle bounces around. In traffic it will head for red, but comes down with revs so thats like the viscous again. On teh motorway if I sit at 60 in third the temp goes to the qtr mark, put it into 5th and it goes towards 3/4.. and I lose fluid.

One intersting point, the large hose not the top hose that goes to teh thermostat housing is being hiot by the viscous, its worn nearly to the canvas, there is a new one on order, but why is this expanding so much that its hitting the viscous and is this stopping the fan?? once t rest with bonnet open it doesnt touch it....

Its breaking my heart

Tue Oct 31, 2006 10:37 am

I'm affraid you'll have to trace your coolant. Where is it going ? It's either outside or in the head

as said above - it's unlikely that a new viscous coupling go wrong. Mine has just 100 miles...maybe the silicone inside needs some time to get scrambled

Tue Oct 31, 2006 1:50 pm

well its coming out the overflow of the expansion tank - which is why I thought it was being over pressurized. It was via the dead waterpump sucking in air... but its still not right.

Tue Oct 31, 2006 5:21 pm

mhhmm now I get your point...that was my case indeed, but not in this proportion and I think we have the same early-type kind of expansion tank too...My basics in physics say: when you boil water in a closed recepient you higher the pressure...I think I solved this problem whith the new clutch, not with the expansion tank cap.
I am sure about the state of my head and head gasket....are you certain about yours...?

Tue Oct 31, 2006 10:27 pm

Green-blood ... I hate to say it but that really sounds like a blown head gasket.
I would also start loooking at the heater matrix to see if that has started leaking.

G

Tue Oct 31, 2006 10:43 pm

nah heater matrix is fine

mechanic did 2 compression tests but it could be accross the water jacket...

its weird, I waws experimenting ont he way home, in heavy motorway traffic, think M25 only with half the lanes!! Anyway, its like the fan is only working with revs, keep 3K on the clock and its sits fine (revs now not speed
), idle and it edges up in temp, very odd... the viscous should spin up the fan faster based on temp not revs