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Repair gone wrong

The car is a 2003 Misubishi Eclipse. Now they are telling me that it is a hydraulic tensioner adjuster and that the bolt that broke on the bracket is what caused the belt to break. They said they only changed the timing belt because it got antifreeze on it during the water pump/coolant pipe install. They said the tensioner looked new so they didn’t think it needed to be changed. They said this even though they have said that other work done previously on the car did not seem to be done to a very high standard. So now, somehow the bolt that holds the tensioner onto the bracket was apparently over tightened by previous mechanic and they never removed this bolt until the belt broke because the belt just slipped on over it, but that it was just snapped in two. If the bolt broke how did the belt snap from being too tight? Would the belt have not become more loose if this were the case?

It almost sounds to me as the new belt caused the bolt to break.
How does an overly tightened bolt holding the tensioner to the bracket just break?
How do they know it was overtightened?

Sadly, you’re now paying the price for slipshod mechanical work. And the people that did it are BSing you. Morally the mechanic is responsible for the subsequent damage. Legally it might be tough to get a recovery. Keep all your paperwork and consider small claims court. Maybe you’ll get lucky and the judge will be familiar with that shop.

Sincere best.

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As I said in another thread, I’m the luckiest guy in town. I made it to 190,000 miles without timing belt problems. The dealer that bought the car said the engine ran better than they thought it might at that mileage. I sold it because I didn’t want to do the 210,000 mile timing belt service which almost certainly would have included oil seal, tensioner, and pulley replacement. With all the extra work, I imagine the price would push $2000. That’s more than I was interested in putting into the car.

I think there’s different style of timing belt tensioners used, varies by make/model/year. Some types (usually the ones on newer cars) require no adjustment, others like on my 25 year old Corolla do require adjustment. I have to loosen the tension on tensioner to get the belt on and off, then after the new belt is installed I have to tighten it back up again to get the proper belt tension.

I’m guessing in OP’s car’s case the tensioner is the non-adjustable type, but what happened is one of the bolts that holds it on to its bracket broke, presumably b/c that bolt was over-torqued during the belt install. Then it finally gave way, the tensioner came loose w/the engine running, didn’t provide enough tension to keep the timing belt on the pulley’s, and the belt entirely slipped off its path. Crankshaft turning, camshaft not turning. Big, bang , boom, valve damage.

The timing belt tension on my Corolla is checked by pressing on the belt, it should deflect 5 - 6 mm with a 20 N force. If it tests incorrect during the install the tensioner has to be re-adjusted, then the timing marks re-checked. The tensioner on the 4AFE engine is a fairly simple device, really just an idler pulley with an offset cam to make it adjustable, and a spring that pulls it towards the belt path.

If the bolt did indeed break, my guess is because it was cross-threaded or buggered up in some other way, during the timing belt job

The engine in your car has an auto adjuster. Different from the link above that is for the older Mitsubishi’s with the Chrysler engines. When replacing the timing belt the auto adjuster is placed in a vise to compress the piston before reassembly.

The reason things break after a timing belt replacement is because mechanics use air tools and over tighten, cross thread and break bolts while working on vehicles. We replace hundreds of timing belts each year and do not need to replace tensioners or pulleys, they just do not fail.

It would likely make no difference if a new tensioner was installed, people break bolts with new or used parts.