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Subaru Idler Pulley & Camshaft Belt Failure

My mechanic replaced our '99 Subaru Impreza camshaft timing belt at the recommended 105,000 miles. Two nights ago, whilst driving home, my wife heard a loud noise under the hood. Now, with 160,000 miles on the odometer, the bearings inside the idler pulley have self-destructed, killing the camshaft belt. My question: should my mechanic have replaced the idler pulley when he replaced the cam belt at 105K miles? In other words, should he have “known” to replace the pulley - “preventative maintenance” in other words - and thus saved me the labor of replacing the cam belt TWICE in 160K miles? Or was there no way of knowing that the idler pulley would die, leaving my mechanic with no liability? Should we split the cost, or should I be responsible for the whole amount, since “these things happen”?

Yes, the proper recommended procedure is to replace all idler and tensioner pulleys at the same time as the timing belt, along with the water pump.

The bigger issue is that the engine on your car should be an interference fit, which means engine damage occurs when a belt breaks. This is caused by the intake valves in the cylinder heads making contact with the pistons now that they’re out of sync.
This can be easily determined without having to replace the timing belt, etc.

Another issue may be going after the mechanic 55k miles later. That’s going to be a dicey issue even though he certainly should have changed idlers, tensioners, etc.
Your vehicle is in deep trouble here.

There are several idler pulleys, I believe, on this engine. Replacing them is optional when the timing belt is replaced. It might be a good idea, or it might be a waste of money. It’s a matter of opinion. Either way, going back after 55K miles is a long shot.

I installed a new timing belt on my Subaru and didn’t replace any of the idlers. They all felt smooth and tight. One could go tomorrow, or they could all last until the next timing belt replacement. One never knows.

I’m sure your mechanic checked the idlers when he installed the timing belt 55K miles ago. He must have felt that they were OK. I’d rack this up to “these things happen.”

I think you have more problems than just a bad idler and a broken belt. The engine in your car is an interference design, meaning that if the cam belt breaks the valves and pistons collide. There is almost surely internal damage. This is going to be expensive.

I agree with both ok4450 and with mcparadise.
In theory, the idler pulleys should have been replaced along with the belt tensioner.

However, if your mechanic was trying to save you some money, he likely checked the condition of the idler pulley and decided that it was in decent shape. A bit of a gamble, perhaps, but since the biggest complaint from customers is always the size of the bill, he was probably trying to cut costs a bit for you.

Unfortunately, that gamble wound up costing you a lot more money. The problem at this point, as both OK and mcp pointed out, is that any component can fail after 55k miles. If the bearing in the idler pulley failed…let’s say…5k or even 10k later, you might have a valid gripe, but the bearing in that pulley could not have been in obviously bad shape when the mechanic worked on the car if it actually lasted another 55k miles.

Incidentally, before a bearing in a pulley seizes up, it usually can be counted on to make a progressively louder squeeking noise for…at least a few weeks, if not a few months before it actually seizes. I have to think that you and your wife were not as attentive to new noises coming from under the hood as you should be, as there should have been an auditory warning of steadily increasing volume for at least a few weeks prior to the incident.

I’m sorry, but I don’t think that you have much of a case.

The reason behind always replacing them is to avoid just what happened here. Inspection by hand of an idler or tensioner bearing doesn’t mean much on a high mileage bearing because they can disentegrate very quickly once pitting or wear through the hard coating occurs.

Those bearings may feel fine one minute and a 1000 miles later may be scattered. Old congealed grease, pitting due to the hard coating wearing through (which can happen quickly) and the bearing will not last long once this happens.

I would liken this to replacing a clutch on a manual transmission car. While the transmission is out it’s a very good idea to replace the rear main seal even if it’s not leaking. Many a transmission has been reinstalled only to have the seal leak a few months later and back out she has to come for a labor repeat.
Same thing with installing a used automatic trans. Always replace the front pump and extension housing seal to head off the inevitable.

The mechanic made an error and it may be very difficult to push this issue after so many miles. Do NOT let a shop tell you that they must install a new belt and tensioners at your expense to determine if a problem exists.

Thanks, everyone, for the advice - well, now I know: if you own a Subie, always change the idler pulley when you change the timing belt! I few extra bucks, but hey, the alternative is more money down the road - As for my mechanic: he is an honest guy, but tries to save me money, so I do share in the blame, in that, I always ask him “Is this necessary?” when doing repairs… Although, let me qualify that statement: I DO believe in preventative care when it comes to cars (especially after living in the Mojave Deserrt, where a broken belt = death!). Hindsight is always 20/20, isn’t it? Thanks again.

Oh, as an aside: my wife stopped the car BEFORE the belt broke, so the motor wasn’t destroyed. And and we DID hear noises a week earlier - it sounded like a loose heat shield - and we were planning to take the car in - the LOUD noises started just 20 miles before returning home - another close call!

What do you mean, stopped the car or stopped the engine? If you mean the car was not rolling but the engine was running when the belt broke damage can still occur.

Some years back my daughter bought a Mitsubishi in which the timing belt and tensioners, etc. had been replaced. They skipped the water pump at this time.
Six months later the water pump started oozing coolant and this saturated the timing belt; which meant dad had to go in there and redo the entire thing.
This is a good example of why you do it all at once.