Timing Pulley Falls Off

Our daughter and son-in law have a 1996 Subaru Outback with 134,000 miles. About 4-5 months ago they had the timing belt replaced.

Three weeks ago the pulley (bolted to the end of the crankshaft) that drives the power steering and air conditioning, fell off. The mechanic has replaced the pulley, bolt and locking pin and wants to charge $275 for the job. He states the pin broke, causing the pulley to wobble and wear, the bolt to come loose and the pulley to drop off.

When the timing belt was replaced, assuming all the parts were in good condition and the bolt attaching the pulley to the end of the crankshaft was tightened to the proper torque, is it feasible the locking pin would break and the remainder of his sequence of events occur? (Question #1)

I think his work is partially, if not totally, responsible for the problem and he needs to cover the cost of correcting the problem. Is this a reasonable request? (Question #2).

I am not trying to hammer the mechanic. He is a good person, but I question his logic on this problem.

I would say that 4 months ago may be too long to enforce a warranty issue, depending on the mechanics written statements on the work order. We are also talking about a twelve year old vehicle, and I think it is best to pay the bill and move on. If you don’t like or believe the mechanic, find a different one for next time.

“Locking pin?” There is a key on the crankshaft, is that what he claims broke? It doesn’t “lock” anything, it just imparts the motion of the crankshaft to the pulley.

If the key broke the pulley could start to move around, wear, and eventually loosen the bolt and fall off. This is unusual, but not impossible.

I’d be worried about wear to the crankshaft end, too, and not just the pulley. If the shaft is worn a new pulley won’t fit correctly, and the same thing could happen again.

I suppose there’s nothing left of the broken key to inspect, is there?

It may be near impossible to prove anything but it’s a bit conincidental for this to happen so soon after the belt replacement.

I agree with mcparadise about the possibility of the crankshaft nose being damaged.
The “locking pin” you refer to (actually a Woodruff key) is made to fit tight into the slot in the crankshaft nose.

If the crank pulley bolt is not properly tightened and the pulley is allowed to wobble for a while it will wallow out the Woodruff key slot to some extent.
If the slot is wallowed out at all then any repair will not last.
It’s entirely possible for an improperly tightened pulley bolt to fall out months later; and also why pulley bolts should be installed with Loc-Tite and properly torqued IMHO.

Since it sounds like it has already been reassembled it may be too late for you or anyone else to check the fitment of the key in the slot. If it is only a push-in fit with the fingers due to the slot suffering some damage then that is not good enough. There will be some more problems on down the road if this is the case.

I would also add that it may be difficult to properly tighten the crank pulley bolt due to the awkwardness of preventing the engine from rotating while tightening the bolt.

A special tool is available to aid in this procedure but the lack of a special tool can be gotten around very easily, IF they chose to do so.

My feeling is that it’s possible due to difficult access that they may have simply used an air wrench with an extension and wobble socket to tighten the bolt.
When an extension is used at an angle along with a wobble socket the torque will not, cannot, be close to what is recommended due to the angles involved.

Hope some of this helps.
(You could abruptly ask the mechanic what he torqued the bolt at just to see how quick and accurate a response you will get. If you get a momentary deer in the headlights look…)

The mechanic could just claim he doesn’t memorize all torque values of all the cars he works on. He could be lying but how could you dispute it?