Crank pulley warning.

[Ian Jones]

When I recently came to change the timing belt on my '93 Cappo I discovered that the engine crank pulley (twin 'V' belt) wasn't tight on the crank to the extent that the Woodruff key had worn in half and the pulley keyway was also damaged. I managed to source a s/h pulley but when they removed it that had also suffered in exactly the same manner. I will re-build mine with a drop of Locktite on the bolt.
May be worth while checking this on your car. New pulleys are £160.

[Ian Linden]

My experience was the opposite, I'm glad to say. The bolt was so tight it required two sets of hands and a strong boot to shift it!

I torqued it up to the stated value, so here's hoping it's ok.

As a point of interest, was there any symptom of uneven timing or anything else from the looseness?

[Murray Betts]

I've not heard of this being an issue but a good heads up, cheers.

Having spent many years in engine development I've seen various issues with crank pulley/damper fixings. It's very common to see "fretting" between the crank nose and pulley bore, it's a consequence of very small movement between the surfaces which is inevitable with any parallel bore design. You get the typical "cocoa powder" brown rust in the joint. Of itself it's usually nothing to worry about. The alternative is a taper, but even those aren't immune and have other issues (and cost) so it's something we live with to some extent.

Remember that the key is only for alignment, it should not take any drive through it, that should be entirely by friction due to the clamping load. Some engines have used "friction washers" which are impregnated with vary hard grit (often industrial diamond powder) to make a mechanical grip between pulley and crank, but that's a last resort really.

The most common reason for crank bolts coming loose is incorrect tightening in the first place, either under or over-tightening will do it. If in any doubt it's advisable to renew the bolt, but if in good condition with no obvious damage they can be re-used with no issues.

[Ian Jones]

My experience was the opposite, I'm glad to say. The bolt was so tight it required two sets of hands and a strong boot to shift it!

I torqued it up to the stated value, so here's hoping it's ok.

As a point of interest, was there any symptom of uneven timing or anything else from the looseness?

It was the twin 'V' belt pulley for the altanator and air con so there is no timing marks and the pulley can be 180 degrees out. You would have thought rust would have fused these parts together but not in my case. The car in question has only done 38,000 and Ive owned it for 5 years and never had reason to removed the crank pulley before.

[Ian Linden]

Ah , I got confused - It's the camshaft belt pulley that affects the timing when it's keyway suffers that defect. Plus I was thinking of setting the ignition timing with a timing lamp on the belt pulley, but that was way back before the days of electronic ignition. Old age