This is the tensioner that came out of my car. It only has about 6000 miles on it. When you try and press it down, it sticks. Now and then it will not pop back out right away either. Look at the scoring on it too. I was shown another that had over 100k miles on it that did not have the same type of score marks on the piston. Lets discuss...
What kind of oil do you run? And do the score marks line up with full compression or somewhere in the middle? Is the tensioner hydraulic or is there a spring inside?
Since the rebuild up until this latest oil change it has been Royal Purple. The last oil change not more than a hundred or so miles ago at best was Motul. The marks are at a point where the tensioner is barely pushed in. No idea if there is a spring in there or not. Possibly as one can push it in and it pops back out, most of the time.
Warning this contains a serious thought Here is what I think. I know I'm a smart arse, but this is a rare serious moment. ***Rare serious thought*** I think it is possible that was cause by swarf. Pieces parts left over from the machining process. Either from the rebuild or possibly from the manufacturing of the tensioner. It does not take much to score up a piece like that. In my opinion that was not caused by the type of oil, just some junk in that oil. If you do not have a magnetic drain plug I'd install one. I'd also do a few short mileage oil changes just to make you feel better. I think Gnat will be all right.
I do have a magnetic drain plug. I did look at the amount of crud on it at that the last oil change. I'd seen worse in this engine. Sorry, I neglected to take a picture this time. This is from engine after the first oil change that was preformed after the Dimple Magnetic Drain Plug was first installed. This last oil change had less than this image shows. I'm not at all discounting the "swarf theory" Chad and I discussed this possibility way back when the first tensioner failed after the rebuild.
Well check that one off. I know your engine was built with utmost care. I'm not laying this on Chad at all. Stuff like this just happens from time to time. That tensioner has a spring inside, but uses oil to maintain tension on the chain. My guess is that thing stuck in causing the timing chain to gain slack & skip the teeth.
Have to agree with Crashton, sounds like crud was in the part when it was installed, luck of the draw.
More notes and pictures on the tensioner adventure, I performed this latest tensioner replacement. I found the tensioner almost fully compressed with the piston protruding about 3mm. When compared to a new tensioner Gnats part felt nearly identical, that is to say somewhat crunchy in its compression stroke. I compared the roughly 6,000 mile tensioner with a 100,000 mile unit and found no scoring on the high mileage unit. The high mileage part also has a defined wear spot on the engagement face of the piston where it was contacting the tension rail. Gnats part was clearly spinning in the bore and had a light wear ring where it contacted the tension rail. Left = new, center = gnats, right = high mileage part Rotation vs. stationary High mileage part
Improper hardening of the original part, or extreme temperature while in use? To me it just looks like Gnat's piece was not as well hardened.
I've been told it is not supposed to rotate and that the markings that the high mileage one Anson posted a picture of is normal.
Any chance it was a defective batch/counterfeit part? Might want to have the re-builder ask his part supplier... My one thought is that since the Gen1 Tritec motor plant was dissembled, and sold to China, where it is still churning out TRI-Tec motors for a pair of Chinese only consumption makes.......some NON-MINI supplied parts might be cheap Chinese parts, that were supposed to be used in CURRENT production motors...undoubtedly a much lower quality than when MINI/BMW and Chrysler were involved....
:cornut: Those marks are verticle not horizontal. They come from in and out motion and not rotating motion. The male piston a loose fit in the female cylinder causing initial woble until fully lined up by cylinder? Jason
On the top of the cylinder the marks show it was spinning. Look at the one that has 100k miles, on the top you see it has a single wear mark. Now look at mine that just came out of the car. You will see that there is a faint circle on the top wear the manufacturing grinder marks have been worn away.
I think Jason is right though. Yes, the piston was rotating so you see a pattern of score marks around the circumference of the piston and a circular wear ring on the end of the piston. But it looks to me like the individual score marks / scratches are vertical, aligned with the compression motion of the piston.