Continued Viscous Fan Issue - Matching Engine Speed

[Scooblitz]

Hello

Just spent the afternoon replacing the v-ribbed belt and putting on a new Meyle viscous fan and blades.

The reason for replacing the viscous coupling was due to the fan being locked on/matching the engine speed. It is on constantly and sounds like a bus. There have now been 3 viscous fans installed on the car and neither of them have worked.
The original which was deemed faulty for obvious reasons, a cheapo ABC viscous fan which was deemed to be faulty on arrival as it did the same and now a new Meyle unit which has not changed the issue.

The issue would appear not to be the viscous coupling itself leaving me to wonder what would cause the fan to be locked on permanently?


Answers on a postcard.

Scooblitz

 

[Scooblitz]

 

[BillyB]

Hi @Scooblitz . Is your engine running too hot and causing the fan to stay on as the bi metalic strip is hot and letting the fluid into the fan therefore trying to cool off things. Just a thought,

 

[Scooblitz]

View attachment 200623

Hi @Scooblitz . Is your engine running too hot and causing the fan to stay on as the bi metalic strip is hot and letting the fluid into the fan therefore trying to cool off things. Just a thought,

Hi Billy.

Viscous fan was installed on a cold car today.

I suspect having had 3 different viscous units on it that its not an issue with the coupling itself. Bit of a mystery as everything has pointed to that so far.

 

[Mike Fishwick]

It sounds as if the pin at the centre of the clutch is stuck.

Does the fan turn freely by hand when the engine is cold - or if removed, is the drive nut free to rotate relative to the clutch?

Also - is the pin in the centre of the clutch free to be moved by the bi-metallic coil? Try slowly pouring some almost-boiling water over the coil and check that there is a difference in resistance between the clutch and its drive nut.

 

[Scooblitz]

It sounds as if the pin at the centre of the clutch is stuck.

Does the fan turn freely by hand when the engine is cold - or if removed, is the drive nut free to rotate relative to the clutch?

Also - is the pin in the centre of the clutch free to be moved by the bi-metallic coil? Try slowly pouring some almost-boiling water over the coil and check that there is a difference in resistance between the clutch and its drive nut.

Hi Mike

Thanks for your response.

The fan and viscous coupling unit are new and fan runs freely by hand when engine off.

Usually on start up the fan spins a little but could be easy stopped by hand. I dare not stick my hand in on idle to mine.

My guess is that there is an issue with the transfer of rotating from the engine, through the water pump and into the fan.

The mechanical element of how the viscous fan works is being superseded by an issue where the engine speed is dictating the fan speed. All the way up to red line, scary.

Fan will be coming off for now.

Electric fan conversion in offing.

 

[Mike Fishwick]

My fan, in common with every other I have seen, runs at roughly engine speed due to viscous drag in the coupling - have you compared it to other cars? When it cuts in it sounds like a fire syren, but this only occurs when the engine is really hot, such as when idling at the top of an alpine pass.

 

[Nodzed]

On tick over the fan should be matching engine speed hot and cold, not spinning slower, if you can grab the fan at tick-over without using a cloth or rolled up news paper to stop it its knackered, the slip comes when the engine is revved unless cooling is required then the slip becomes progressively less. If its locked, at about 3000rpm it will sound like a WW2 Spitfire and be very obvious.

 

[the Nefyn cat]

The only thing that decides the speed of the fan is the viscous hub itself, and that is temperature dependant. Must be a faulty hub (again) if it's running at engine speed all the time.
FWIW, my car's been running without a fan for the last few years with no problems, and that's in the sub-tropical paradise of the Lleyn.

 

[Scooblitz]

Thanks all who have replied.

Strangely, it now appears to be working.

Fitted the new Viscous clutch last night and gave it a few revs and was whooshing like a bus. Perhaps if I had let it idle for longer it would have settled down.

It seems to have just done that. Fingers crossed, it will stay working as designed.

It still runs quite quick on idle. More so than others I have seen but doesn't have anywhere near the sound of a bus.

3rd Viscous fan could be the one.

 

[Scooblitz]

The only thing that decides the speed of the fan is the viscous hub itself, and that is temperature dependant. Must be a faulty hub (again) if it's running at engine speed all the time.
FWIW, my car's been running without a fan for the last few years with no problems, and that's in the sub-tropical paradise of the Lleyn.

Been running the 'viscous delete' for 18 months now and have had no real issues without one, even in Sub Saharan Glasgow.

Well, when I say no issues. There's been a few. As @Nodzed will remember on last years Scottish Run, if there is a traffic jam or slow moving traffic on a warm day, it will over heat quite quickly. Leaving me inside (with the hardtop on) with the heater blowers up to 11 trying to bring the engine bay temp down.

I decided to re fan for traffic jam reasons in Scotland which are too common and the Highland roads.

Car went in for oil last weekend and my car comes with a small list of nuances, one of which is don't leave it idling for more than 5 mins or its going to blow. Its nice knowing it won't overheat if ever in the hands of unwitting mechanics who don't get the memo.

 

[Nodzed]

This intelligent component improves engine efficiency by regulating the RPM of the engine fan and cool air supply. The bimetal sensor contracts closing the valve, so the silicone fluid remains in the reservoir chamber. At this stage, the viscous fan coupling is disengaged and turns at around 20% of the rotation speed of the engine. The bimetal sensor expands, rotating the valve and allowing the silicone fluid to move through the entire chamber to the outer edges. This generates enough torque to drive the cooling fan blades at engine operating speeds and remain at a consistent temperature. At this stage, the viscous fan coupling is engaged and turns at around 80% of the rotation speed of the engine. It is good practice to always check the condition of the viscous fan coupling when the water pump is replaced. A worn coupling will directly affect the water pump’s lifespan. A failed viscous fan coupling can stay stuck in the engagement position meaning it will always run at 80% of the engine rotation speed. This can cause disruption with high noise and vibration, making a loud whirling sound as the engine is revved and will increase fuel consumption.

On the other hand, if the viscous fan coupling fails in the disengaged position, it will not draw air through the radiator. This in turn will lead to the engine overheating as the cooling process is disrupted. Leaking silicone fluid, disengaging the fan coupling.

The bimetal sensor governs the functioning of the viscous fan coupling. Primarily, there are two kinds of bimetal sensor systems: plate and coil. Both of them work under the same principle, as explained previously.

 

[Nodzed]

Been running the 'viscous delete' for 18 months now and have had no real issues without one, even in Sub Saharan Glasgow.

Well, when I say no issues. There's been a few. As @Nodzed will remember on last years Scottish Run, if there is a traffic jam or slow moving traffic on a warm day, it will over heat quite quickly. Leaving me inside (with the hardtop on) with the heater blowers up to 11 trying to bring the engine bay temp down.

I decided to re fan for traffic jam reasons in Scotland which are too common and the Highland roads.

Car went in for oil last weekend and my car comes with a small list of nuances, one of which is don't leave it idling for more than 5 mins or its going to blow. Its nice knowing it won't overheat if ever in the hands of unwitting mechanics who don't get the memo.

we did wonder what would get you first, heat exhaustion with the roof up or the midges with it down

 

[Dino D]

Been running the 'viscous delete' for 18 months now and have had no real issues without one, even in Sub Saharan Glasgow.

Well, when I say no issues. There's been a few. As @Nodzed will remember on last years Scottish Run, if there is a traffic jam or slow moving traffic on a warm day, it will over heat quite quickly. Leaving me inside (with the hardtop on) with the heater blowers up to 11 trying to bring the engine bay temp down.

I decided to re fan for traffic jam reasons in Scotland which are too common and the Highland roads.

Car went in for oil last weekend and my car comes with a small list of nuances, one of which is don't leave it idling for more than 5 mins or its going to blow. Its nice knowing it won't overheat if ever in the hands of unwitting mechanics who don't get the memo.

Something doesn’t sound right with your aircon fan.

I ran without the viscous for years and the only time the gauge moved was at Lydden Hill on a 30c track day chasing @spurs fan in a coupe .
I had the aircon running as well which didn’t help but don’t like get sweaty on track .

my aircon fan was wired up wrong so never kicked in as it was supposed to when the aircon was off. Early cars like ours were affected by this dodgy wiring - I put a write up that I found in my build thread.

If it’s that it’ll solve your problems and should cope with the Scottish weather just fine!

I’ve now added an electric fan but that’s because of track use.

 

[Scooblitz]

Something doesn’t sound right with your aircon fan.

I ran without the viscous for years and the only time the gauge moved was at Lydden Hill on a 30c track day chasing @spurs fan in a coupe .
I had the aircon running as well which didn’t help but don’t like get sweaty on track .

my aircon fan was wired up wrong so never kicked in as it was supposed to when the aircon was off. Early cars like ours were affected by this dodgy wiring - I put a write up that I found in my build thread.

If it’s that it’ll solve your problems and should cope with the Scottish weather just fine!

I’ve now added an electric fan but that’s because of track use.

Sadly, I don't have aircon so there is only the viscous fan for cooling.

I was looking up some Spal fans and bits for the electric conversion before it seems to have started operating as it should.

If the car is moving, airflow has been enough to cool the engine without issue. Needle has never moved above middle position.

 

[Mike Fishwick]

As a matter of interest, my daughter's one-lady-owner E46 coupe was never fitted with a viscous fan - just the aircon fan.

 

[Ianmc]

As a matter of interest, my daughter's one-lady-owner E46 coupe was never fitted with a viscous fan - just the aircon fan.

My 1997 M44 also does not have a viscous fan from new.

 

[Dino D]

As a matter of interest, my daughter's one-lady-owner E46 coupe was never fitted with a viscous fan - just the aircon fan.

That’s interesting - was it a 4 or 6cyl car?

 

[Mike Fishwick]

six - 2.5 litres.

 

[AirOps]

Dino D., I have read the comments about the early 6 cylinder cars having the wiring for the Aux fan "wrong", I am not convinced that the wiring is "wrong" in my opinion the wiring is in fact as intended by BMW. The fan switch in the radiator has settings for 90/99c, I believe that BMW intended the "Low" speed on the Aux fan for cooling with the A/C on (not controlled by the fan switch) and the 90c switch point to be for "High" speed for overheat protection. I think the 99c setting is redundant and effectively not used (economy of scale on fan switch's), having the Aux fan High speed coming on at 99c would not provide a whole lot of "Overheat protecion". On my 97 2.8 the Aux fan comes on low when the A/C is switched on and on high if the temperature gets to the 90c. I am planning on replacing the mechanical fan with a Spal electric fan controlled by a M44 (80/88c) fan switch, using the 80c setting to control the Spal fan and the 88c setting to control high speed on the Aux fan. The car will be used in South Florida for most of the year, so overheat protection is justified.