(Home) Crankshaft pulley (i think)

I bought a townace a couple of months ago and have just got round to pulling out the front seat etc. to have a general check up. The belts looked a bit tatty so I thought that I would replace them while I was there. PS belt came off easily enough. From what I have read on here I was expecting loosening the alternator to be a bit more difficult with hidden bolts and the like but mine seemed to have the old fashioned fixed pivot and sliding lock bolts (just like the power steering.

But when I tried to pull off the twin alternator belts, the whole ring on which they are mounted just slid off the centre bit of the crankshaft pulley. As if the only thing holding it in position was the tension in the belts. Ace Answers talks a lot about the crankshaft bolt shearing but that seems to be fine. It is still attached to the front of the engine but with no mechanical connection to this ring. And the whole unit seems to have been machined this way as nothing resembling a shear line is visible.

The power steering pulley is still nicely attached to the crank so no problems there. Could a previous owner have neglected to replace a plate of some sort that holds the whole lot together. Or is this correct and the whole unit is held together magically somehow.

I am totally puzzled.

- (#13705) Dave, 11 Oct 04 16:05

Dave, do you mean that the whole of the pulley assembly was floating, ie, with the crankshaft securing bolt in situ? There should be a large washer under the bolt head and this pulls the pulley hub onto the key and up against the timing belt pulley inside the plastic belt cover. Or, are you saying that the central "hub" of the pulley was still secured to the crankshaft, and the outer, vee grooved part of the pulley, has, somehow become detached ? If so, I did not think that the double pulley was in two parts but,so I believe,the earlier pulley, with a single belt/groove, had a bonded rubber "shock absorber" between the crankshaft boss and the outer, grooved section. I have not heard of this happening before and, have you, possibly, got a non standard pulley fitted? Others might like to confirm if any of the double groove pulleys (or all of them) have this rubber bond. However, with the bond broken, how has the fan/alternator/ PS pump been running?

- (#13705) John Davis (Leics), 11 Oct 04 16:19

It is exactly as your second description. When I took off the twin belts I found myself holding what appeared to be a tall and substantially heavier version of the little hoops that I used to throw over teddy bears at the fairground when I was a kid. On one face (the outer as it came off) are six small holes drilled in a few mm and equally spaced over about a third of the circumference. This hoop is about twice as wide as the depth of the groove. If it ever was joined to the inner part by some sort of rubber then this has vanished leaving no trace whatsoever. Both inner and outer faces along with the inner surface facing the crankshaft are clearly machined but not finished with a polished surface.

Yet the car has been running quite happily recently. This was just a spot of routine maintenance and had my local factors had the fanbelts in stock today I would have quite happily reassembled everything and just have thought of it as odd. It is only after thinking about it for a while that I started to feel that it didn't seem quite right.
- (#13705) Dave, 11 Oct 04 17:07

As John says, the outer pulley should've been attached to the inner hub via a bonded rubber layer, about 1/8" thick, as I recall. It's not unknown for the bonding to come undone, and not just on Townies. You'll need to confirm whether the pulley hub still has the rubber on it's perimeter or not. If not (and there'll be a large, obvious gap between inner and outer), you'll need a new pulley for sure. But if the rubber's still there, you *might* just get away with cleaning all well, coating both items with a good quality adhesive- silicone might be the job- and pressing the ring back on.

- (#13705) David Miller, 12 Oct 04 01:21

Dave, this still seems a bit unusual and, I can't quite see how the ancilliaries were still being driven.
Perhaps there was, almost, a heat generated bond between the outer diameter of the crankshaft boss and it's disconnected pulley. If you care to go back to the homepage and click on "tasks", my little article on the making of a crankshaft pulley locking device, shows a single groove pulley and the rubber bond can be seen. It does appear that your next move is to find another pulley, unless you are able to re-bond the two components as suggested by David. This would have to be done carefully to retain concentricity and reduce any "out of balance". The easiest way might be to get a sleeve turned up,with an interference fit between the two components and forget about any shock absorbing facility. I think the archives will show links to s/h suppliers where some of our fellow Ace owners have had the dreaded pulley drop off.

- (#13705) John Davis (Leics), 12 Oct 04 04:44

Thanks to both of you for your help. On reexamination in daylight it appears that the rubber is still attached to the inner hub (and very firmly attached) but seems to have seperated entirely from the outer pulley wheels. Yet very strangely this seems to have had no discernible effect on the operation of the fan and alternator despite some very heavy use this summer. The pulleys driving the power steering and the air con are still firmly attached as they should have been. I guess that the tension in the alternator belts pulled the wheel over to one side and created sufficient friction to keep everything working. The central hub of the pulley must have been reasonably well balanced and the outer pulley wheel, permanently pulled towards the alternator, acted as a driven wheel rather than an imbalanced lump of metal.

If the pulley has stayed in place this long with no attachment then I may be tempted to give gluing a try. Do you really think that a silicon glue would stand up to the shearing forces developed here? In such places I would usually use an epoxy but those break down under heat and I guess that this pulley gets fairly warm. Does anyone have any suggestions for something easily obtainable. Superglue would need a lot tighter fit. Could rubber glue (the stuff designed to fix holes in trainers) do the job? And by silicone do you mean the stuff used to seal the edge of baths and showers?

- (#13705) Dave, 12 Oct 04 15:09

My guess would be that epoxy is too hard/ brittle. Might be worth a try tho. A rubber solution of some kind would of course be ideal, except they tend to be contact adhesives and you've got to slide the ring onto the hub.

If you do want to try silicone, make it one of the sticky high temperature ones- try your local plumber's merchant, as they use it for flues etc...

- (#13705) David Miller, 12 Oct 04 22:40