Viscous Coupling Failed Again

[stag-phil]

Less than a year ago the viscous coupling failed on my car causing the fan blades to eat into the radiator.

A replacement fan and radiator from paddocks and a VC from Bob was fitted but 10 months later and the VC has failed resulting in the same damage as before.

The VC has been removed and the engine is being kept cool with a kenlow fan while I decide what to do.

I can’t believe it is faulty parts I am more inclined to think it is something to do with my car.

My fan blades are very close to the radiator, is it possible that at speed the plastic fan is drawn towards the radiator putting the VC out of balance hence the failure?

I want to fit another VC but am reluctant to do so if it is likely that in a few months the problem will re-occur.

Phil

[malc4d]

I just posted about the different fan/pully setup.

[DJT]

Phil,

The experience of a local member last year leads me to believe that there are some new fans around that are less stiff than the original ones......

[Bob Heritage]

Not known one of these couplings to fail before Phil, I'd be interested to know the cause.

[jleyton]

I'm now on my fifth

I got this one from Bob and it's been good. My blades are very close to the rad but seem ok.

The only slight concern I have is that it feels a tad tight - I only get one or two blades on the spin test.

Good luck Phil.

Cheers

Julian

[mjheathcote]

One or two of the spin test....that's good!
Mine is a genuine Holset coupling, and does the same. It's done about 15k miles.
When they are worn they then spin easily, and thus slip too much at speed and don't have the cooling ability they should.
Sounds like a problem with the blades or an extra thick radiator, clearance shouldn't be so small.

edit: just measured mine and I have exactly an inch/25mm clearance with the original pattern 4 row radiator.

[jeffsstag]

check your engine mountings as when they get weak the engine can move forward and hit radiator,ive had this before heavy braking or a jolt from the road can cause this,just a suggestion cheers jeff

[stag8manod]

As a suggestion, My first Spitfire was an American market one which had a few different fittings to comply with their regulations. One of which was a wire rope restrainer from the one of bottom bell housing bolts back to a bracket on the gearbox cross member (I think). The reason being in the advent of an accident in would retain the engine and stop the shearing of the engine mounts. In your case it keep the engine in place and stop it moving forward during deceleration or braking and possibly prevent contact with the radiator.
Cheers Ian A

[DJT]

As a suggestion, My first Spitfire was an American market one which had a few different fittings to comply with their regulations. One of which was a wire rope restrainer from the one of bottom bell housing bolts back to a bracket on the gearbox cross member (I think). The reason being in the advent of an accident in would retain the engine and stop the shearing of the engine mounts. In your case it keep the engine in place and stop it moving forward during deceleration or braking and possibly prevent contact with the radiator.
Cheers Ian A

Surely the Bellhousing, therefore the engine, is already attached to the gearbox crossmember by the gearbox casing

[Stagsongas]

Less than a year ago the viscous coupling failed on my car causing the fan blades to eat into the radiator.

A replacement fan and radiator from paddocks and a VC from Bob was fitted but 10 months later and the VC has failed resulting in the same damage as before.

The VC has been removed and the engine is being kept cool with a kenlow fan while I decide what to do.

I can’t believe it is faulty parts I am more inclined to think it is something to do with my car.

My fan blades are very close to the radiator, is it possible that at speed the plastic fan is drawn towards the radiator putting the VC out of balance hence the failure?

I want to fit another VC but am reluctant to do so if it is likely that in a few months the problem will re-occur.

Phil

Phil,

When you say the VC has failed, in what way? Can you give us details?

For instance, is the centre portion still in place, is it loose on its shaft or is it no longer free to rotate when the engine is stationary?

Regards

Steve

[stag-phil]

Hi Guys

Thank you for your replies.

This is the second failure of the VC since I have owned the car and both VC’s have failed in the same way which appears to be centre bearing failure.

There is never any indication that failure is imminent but when it fails the ‘wobble’ on the centre bearing allowing the fan to fall onto the radiator, basically the fan flops about.

As far as I am aware it was not slipping or seized hence why I think something is putting the VC out of balance and causing the bearing to wear and eventually fail the end result being that the fan blades can then reach the radiator with obvious results.

Before failure there was not enough space between the centre bolt and the radiator to allow the belt to be changed.

Jeff, the engine mounts seem to be ok but it is a very good point and I think I will replace them if only for peace of mind.

Julian, each time your VC failed did you change the radiator?

Malc4d: the spacer you are referring to I believe is for MK 1’s only. If mine had a space the fan would be inside the rad.

Dave: I also wondered if the plastic fan blade was too flexible and because there is little space between the blades and the rad that is another possible cause.

Anyone know where I can get a good quality one or an original second-hand one?
Going back to the gap between the rad and the fan blades is the solution to have the end of the pulley machined to reduce the length slightly? If so anyone know how much should be machined off.

In fact, are there different length pulleys as that might explain why there is a variation of gaps between the blades and the radiator?

Thanks.

Phil

[jleyton]

Julian, each time your VC failed did you change the radiator?

Thanks.

Phil

Hi Phil,

The answer is no because I've been lucky that, only once did the failure affect the rad.

No 1. Was on the car when I bought it and was seized.
No 2. Bearing play, similar to yours, developed very quickly and damaged rad
No 3. Saw leaking oil on inside of fan so changed before total failure
No 4. Actually didn't fail but very slight traces of oil evident and, as I had just bought a 'good' one from Bob I decided to fit it when the rad was out for another job
No 5. Bob supplied VC that has given good service for around 5,000 miles.

I have an upgraded rad from Rimmers such that I also can't get a fan belt on, despite enlargening the rad mounting holes and other work. But the fan looks original and I don't think the blades bend excessively, even at speed.

One other thought Phil. When my fan went into the rad, it damaged the fins, but didn't actually pierce the core. I was able to carefully straighten the fins. Has your's actually caused a leak ?

Good luck.

Cheers

Julian

[Staggard]

Surely the Bellhousing, therefore the engine, is already attached to the gearbox crossmember by the gearbox casing

The gearbox is rubber mounted as well, he is talking about a restraining hawser from the engine to the chassis mounted part of the cross member. We used to do that with a wire hawser across the front of the engine and bolted to the chassis both sides to stop the engine moving forward in banger/super stock racing.

[davidf]

Are you sure you have the big thick washer under the head of the bolt?

http://www.rimmerbros.co.uk/Item--i-GRID005172

Part no. 155516

I once left mine out, and after a few thousand miles, the fan was rattling and wobbling. All the symptoms of a failed bearing, but it was just loose on the end of the crank. The bolt had bottomed in its thread, and initially just gripped the fan boss, but a little wear, and the grip was gone.

[stag-phil]

I am sure the washer is in place but will check.

I certainly hope the washer is present because if it is missing that will mean the head of the bolt will be even closer to the rad if not touching it.

Phil