Did the timing belt installation cause my engine failure

subaru

#1

We purchased a 2009 Subaru Impreza for our daughter. It had impeccable service records with a large portion of the work done at a local dealership. It had recently had the timing belt changed and the head gaskets done. We were very leary of buying a used Subaru since they tend to have head gasket problems. Our daughter only had it 3 weeks when the check engine light turned on. She took the next exit of the freeway and the car stalled out on the side of the road. When I arrived with the tow truck driver I checked the oil and it was still full. We towed it to the dealership where we bought it and they told us it had a blown rod bearing and the engine would need to be replaced. We took it to another shop to get the engine replaced. That shop owner told us that the timing belt was installed one notch off on one side. He believes it caused the engine failure. It was not broken and was still in place. Is it possible that this could have caused the blown rod bearing? Is it possible that the blown rod bearing cause the timing belt to slip one notch? We’re just trying to figure out if we should pursue reimbursement from the shop who installed the timing belt. Please help!


#2

Have you taken pictures of the timing belt installed incorrectly?


#3

We still have the old engine core. The belt is still installed on it.


#4

I would say no. A timing belt one notch off would make the engine run rough but it wouldn’t affect bearings in any way. The rod bearing developed a problem shortly before or after you bought the vehicle.


#5

Agreed; the cam on one side being off a tooth would not cause a rod bearing problem. One has to suspect a pre-existing condition.

Some of the missing story could be what the engine was doing on the freeway other than the CEL being on. That could mean was there any subtle rattling before exiting the freeway and how far until that next exit, etc.

Seldom ever does a rod bearing just fail unless the engine has been run out of oil and seldom does one ever fail without some kind of warning. That’s all assuming normal driving with no pedal to the metal involved.


#6

Thank you for your response. What doesn’t make sense to me is that if it’s running rough over a period of time, it seems like that could be doing damage in some way. What Type of damage would it cause?

Also, since timing belts need to be installed specifically matching certain points, it implies that in must be done correctly. Otherwise, one would think there would be a range of correct installation points. Right?

Finally, it’s possible that the vehicle did have indications there was a problem. Since we had just purchased the vehicle, we would have no way of knowing if the code had been reset. We didn’t have any indicators prior to the issue in the freeway. The distance to the ramp was less than 1/2 mile.

The vehicle had a rough sound to it. The Subaru dealership said that was a “Subaru” sound. Since we aren’t “Subaru people” we wouldn’t know. We know Hondas and Toyotas, so we thought it was reasonable.


#7

The timing belt synchronizes the valves to the pistons. One click off would mean the valves are opening and closing a little too early or too late compared to the position of the piston in its travel, depending on which way it was off. It’s hard to imaging how that would cause the kind of force needed to damage a rod bearing.

If the ignition timing were off, too far advanced, that could damage a rod bearing or even burn a hole in the piston. But the valve timing a little off, the only symptom I’d expect would be some loss of power and maybe rough idling. If the valve timing was way off, that could cause the valves to hit the pistons, but one click off wouldn’t do that.

One idea, check the valves to see if there’s evidence they’ve hit the pistons.

It’s sort of odd an experienced mechanic wouldn’t get the timing belt alignment correct. It’s easy to be off by a click on the first try, especially if it is configured with two cam sprockets the belt has to ride on, but you are supposed to rotate the engine several times after the first try and double check. When I’ve done it, and it passes the first check, I start the engine and let it idle for a few minutes, then check again, both a static check and a check w/a timing light. I doubt most shops do that, probably overkill. But that’s how I as a diy’er do it, b/c it is a big job to have to redo that task if done wrong the first time and everything is put back together. Checking to verify all the timing marks are aligned is not any more difficult than dialing a school locker combination lock.


#8

I wouldn’t go back to the shop that got the belt wrong, but they didn’t cause this problem. Usually before a bearing fails, they make a knocking sound, like hitting the block with a hammer. Its pretty loud too.

The thing I don’t get, how does a rod bearing cause a check engine light? What was the code? I think there was something else wrong. I really suspect the diagnosis of a bearing failure.


#9

About the only problem that can be caused by a cam being out sync would be possibly an exhaust valve face burning over time or intake valves hitting the tops of the pistons.

Now; it is possible that if the original timing belt broke while the engine was at speed the valves could have whacked the piston tops hard enough to damage a rod bearing. At some point that rod bearing damage could surface and become a problem.

This would only be true if the belt actually broke and not as a matter of routine replacement.
In most cases when a belt snaps on an interference fit engine (Subaru is one) the worst that happens is that some valves may bend and the piston tops will get nicked up.
In most cases nicking the pistons will not harm the rod bearings but as with most things mechanical there are exceptions.

As for the CEL, could that been the knock sensors setting a code due to severe banging in the engine: rhetorically asking.
Knock sensors are generally for pinging issues but since they’re basically Piezo microphones they will pick up any noise.

If a rod bearing has really failed I suspect there was an issue with it before the car was purchased.
Sorry I can’t be precise here.