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Help! Mechanic used a faulty part!

Hey guys, first time posting, just joined the community.

Back in January (2017) my main pulley on the timing belt sheared out that bolt from the engine and the pulley was being knocked against by that metal cylinder behind the main pulley (don’t know what any of it is called). They replaced all the pulleys and tensioner and such.

Now several moths later: the tensioner just came loose and shredded the valve heads and my engine is done for? Kaput. I had it towed to a mechanic (I am out of town so an unfamiliar one) and he said the part must have been faulty (i.e. the tensioner). If the mechanic previously installed a faulty part and it caused my engine to shred itself, who is at fault? Does the part manufacturer pay for a new engine? Does the mechanic? Do I???

Thanks =(

The vehicle was repaired almost a year ago.

If the mechanic had done anything wrong, it would have showed up before now.

You’re the owner of the vehicle. It’s up to you to go after the manufacturer of the replacement part under the warranty of the part.

But most of these warranty’s have provisions where the failed part is covered, but not any damage incurred from said failed part.

So? You put this one under, “Stuff Happens”


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Well, here is the difficult bit, right? I know the mechanic couldn’t have known the part was manufactured poorly or incorrectly, but the company that made the part should be legally obligated to repair any “foreseeable damage” based on the failure of their part to operate correctly, right? That seems only “fair” in my mind. Would I have a legal basis to file against them? Or should I ask on a legal advice forum? hah!

Read the warranty for the part.

It will describe what is covered, and what isn’t.


Generally, the warranty is limited to repairing or replacing the part, if the part is determined by its maker/supplier to be defective. The warranty does not cover the labor in removing and replacing the part, or consequential damages such as costs of other damage to the machinery caused by the failure of the part, loss of income, etc., etc.

I hate to agree with every one else, but everyone here is right. I feel for you and wish I could offer another answer.
You’d also have the problem of proving the cascade of failures, an almost impossible task in a situation like this.

By the way, what year is the Subie and how many miles does it have on it?
Have you gotten a quote to replace your motor with a rebuilt or boneyard motor? If the rest of the Subie is in good shape, that’d be your best option here.


The attorney retainer fee for a law suit alone will probably cost more than the vehicle is worth.


I doubt if the parts were defective. More than likely the mechanic did not do the repairs correctly or there is an issue with your car that caused the timing pulley and tensioner to fail. If you want redress I would recommend small claims court. If you want to go after the parts company, find out where the mechanic purchased the parts and contact the manufacturer. Manufacturers I’ve dealt with in the past have always made good on defects even if the parts were out of warranty (if the parts were indeed defective).
All that said, you didn’t mention the mileage or what caused the pulley to shear. A good mechanic would have no difficulty telling you what the problem was.

tl;dr: I win 75% of the time in these court cases if it even goes to trial

From what I remember, the first time it happened it was due to the bolt simply shearing itself out, which could have been subaru’s fault? But this time is was the tensioner that came out. The subie has over 102k miles on it, the rest of it is still in very nice condition, the quote for a new engine is 4-5k depending on where it is coming from.

In researching legal action, statute 402 claims that the manufacturer is responsible for damages to person or property in cases of a manufacturer selling a faulty part regardless of their warranty. Apparently the warranty applies to the part itself, meaning if that part was only injured they simply replace the part, but if it caused damage to the operator’s property it is on the manufacturer to replace or repair any damage reasonably caused by the malfunction outside of pure economic loss (say if I was trying to sell the car). Apparently the impotus is also on the manufacturer because we (as plaintiff and defendant) are at economic despairities (they having planned insurance to cover such inevitable happenings and Lawyers on retainer whereas a lawyer would only receive payment on this case under a consequential basis that we win) and I am not required to prove that it was a manufacturing error of a specific type (just that it was the tensioner that caused the damage).

At least that is the basic legal counsel that is available through looking at previous court cases in montana (where I live) in such situations. I will keep you all posted on whether or not it gets to that point!


I’m pretty sure the warranty from the part manufacturer states that they will not cover any incidental or collateral damage that results from their part failure. They will only provide a replacement for the failed part.

You’re going to have to contact the garage that did the original work and find out what they think the next step should be. Starting off by seeking legal counsel first without talking to garage #1 will only make things more costly and time-consuming for you. Talk to the garage and see if you can come to a mutual agreement.


Don’t be intimidated by warranty limitations, they define what the manufacturer will do on their own but have no bearing on the determination of a court, if it goes that far.

Take it to a competent mechanic, or maybe two, for diagnosis. If they feel it was improperly installed (or a bad part) take the issue up with the mechanic (or manufacturer) who performed the repair to determine whether you can work something out. Final step would be the legal system but be prepared to share about 1/3 of the settlement with the attorney.

To initiate a lawsuit would be traveling down a long bumpy road. Is the money you will spend worth it? Is the stress you will encounter worth it? Do you have several years to litigate? And after all your time, money, and energy expended are you prepared to lose? Pay for another engine or just junk the car. A month from now you will be a happy camper and not miss the money. Life can be smooth if you travel the right paths.

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What is wrong with motor? Timing belt slipped due to bad tensioner so valves are bent? What yr is car? How many miles?

First, when you say “the tensioner just came loose and shredded the valve heads and my engine is done for”, I presume you are not talking about failure of the the bolts that held the tensioner on.

If so, here’s a suggestion for a possible added angle to consider: see if the tensioner has a known or demonstrable high failure rate (out there in social media land).

That can be leverage for you when going to the part maker, which might not want that information advertised in exchange for a few thousand to take care of your engine.

I would agree to the original @Tester advice - “stuff happens”

Even if OP try go litigious, he would have to prove quite a few non-trivial points.

to litigate against Subaru:

  • did mechanic use all approved tools and procedures?
  • did mechanic use OEM approved parts?
  • what about thread-lock glue if any required? exactly of manufacturer approved sort?
  • bolt sheared… was it torqued right? was it replaced if required by OEM procedure?
  • get prepared for expensive expertise on these steps, some can not be proven like following all steps
  • manufacturer will unlikely be very friendly too as it sure smells of a frivolous lawsuit

to litigate against part manufacturer

  • by accepting part you are bound to warranty it had, 100% it will have "subsequent damages disclaimer’
  • be prepared for most of items from “litigating against Subaru” too…

probably OP would have the best chances suing mechanic and likely pushing him out of business in the end, but if mechanic has a good insurance, they will wear OP down with steps similar to the aforementioned ones

I had a friend of mine to go after BMW on the clear case for the lemon law application, they unleashed a number of layers on him and it was so expensive in the end, he accepted settlement loosing more than $20K in the end, after more than a year of fighting

“stuff happens”, find a better mechanic, get a used engine installed and drive on…

if you are lucky enough, you paid your car repair with a credit card. Some credit cards like Visa provide a free extended warranty of 2 years on anything you purchase. .Most people don’t know that

IANAL, but I’ve worked along some lawyers and kind of have a feel for how these things work.

First is that the only money that can be won in a lawsuit of this type is the cost of repairing the damage. Nothing for the time it takes to deal with the situation and no punitive damages and lawyer’s fees.

Also, there is a principle called “Making them whole”, which means bringing them back to where they were before the incident happened. That means a used engine.

I’m not sure what the whole thing would cost, but I’ll bet it’s under $5,000. (Anyone have a better figure for installing a used engine?)

The good news is that many states have small claims courts where people can argue their own case. The upper limit for damages is $5K to $7.5K depending on the state.

Then there is the issue of proving that the engine failed due to a faulty part. Someone arguing their own case is usually granted a certain amount of latitude regarding evidence.

But the big thing here is that a company is likely to seek a settlement to avoid the cost of defending - and that just might be where our OP is going. My guess is that for a little bit of effort, the OP could get $1,500 to $2,500.

Working used 2.5 Subaru engine is $1000-1500 delivered off eBay, new OEM short-block sells there for $2,000, add half of that to install in independent garage

what was fixed back in january? it sounds like the crank pulley somehow came loose? if so than the timing would have been messed up and i would expect to have valve damage from that? you make it sound like the repair was minor or low cost. or you would have said you paid 2000 to fix the valve damage. now the tensioner for the timing belt fails which is basically the same failure mode. you loose tension on the timing belt and damage the valves again? so you have had 2 major engine damage issues in 1 yr?