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Stock Problems/IssuesDiscussions related to warranty related issues and repairs, or other problems with the OEM parts and software for MINI Cooper (R50), Cabrio (R52), and Cooper S (R53) MINIs.
Unbreakable - Thanks for following this thread and commenting, it means a lot. I will get some photos of the piston skirts this afternoon. There is a little wear on them, but not much. I am very impressed with the way everything is looking. I took a peak at the valve train and crank when replacing gaskets a few years back and everything looked good. But that was a few hundred thousand miles ago, so I wasn't really sure what to expect this time.
All thanks to you Nik. It's a rare opportunity to see a very high mileage engine that I had responsibility to develop. Since I had responsibility for both performance and reliability development, I often had to make decisions about the appropriate trade-offs between the two. The exhaust valve design is one example of that compromise. Although I no longer work for Chrysler or in engine development, it's very exciting to see the results of these efforts 15 years later! No matter how long I've been out of engine development, I'll always been an engine guy.
An interesting side note that I'd almost forgotten about. Since the 1.6L is a "derivative" (in design concept) of the 2.0L SOHC Neon engine, one of the really brilliant (IMO) decisions that was made by the program director, was to go out into the open market and purchase 100,000+ mile Neon's and run teardown inspections of them. I think 20 vehicles were purchased and disassembled (after we drove the cars). We learned a lot from that experience that was directly applied to the Tritec design. The decision for example to use the Grafal skirt coating was one result, as many of those high mileage 2.0L's showed signs of skirt scuffing with the tin plated pistons. Another I believe was the oil gallery system. It was completely changed after the first prototype phase.
A couple pics of the piston skirts for you. These are of piston #1, but they all look about the same. I am planning on getting the cylinders honed, new pistons, and get the head cleaned up (and of course new bearings all the way around). Looking at the condition the pistons it almost seems I could continue to run them. Any opinions?
Nik
Pardon the greasy fingerprint on the upper right. (:
Last edited by -=gRaY rAvEn=-; 03-21-2016 at 10:14 AM.
Without getting actual piston skirt and bore measurements, it's not possible for me to say whether you could just do a light re-hone and new rings. Piston to bore clearance specs. are very tight on these engines. Most likely you could re-use them based only on these pictures. It just depends what you want to get out of the re-build and how much your do or don't want to spend. The pistons look to be in incredible condition given the mileage. It's always a risk/reward judgment call. The piston to bore clearances (at the sizing diameter of the piston) over the skirt coating for new pistons are: - 0.011/ 0.041 mm
Yes, an interference fit at the lower end. Piston pin clearances are also pretty small: 0.002/ 0.013 mm
I don't know what would be considered acceptable "in service" clearances. They're probably listed in the service manual. I do know from experience that when piston pin clearances get up around 19 microns, they start to tick at idle.
AFA the head. I would expect that you'll need new valve guides, seals and valves, with the seats re-cut. Exhaust seats might need replacing. It will be hard to re-cut them if the seats are worn to full valve face width (which is likely to be the case with so many miles). At almost 400,000 miles you're really in uncharted waters, so it's difficult for me to give specific advice without seeing the parts and measurements.
Last edited by Unbreakable Lump; 02-09-2016 at 01:08 PM.
Had company all weekend, but was able to take apart the head this afternoon. Overall it's looking pretty good. Had two valve seals that were leaking a bit. Was able to get the first cleaning in the head, intake valves have a nice seat still, and the exhaust have expected build up. Plan to get them cleaned up this week and see if they are still in spec.
Some cleaning needed on the exhaust valve
Intake valve
All disassembled
First clean up
Last edited by -=gRaY rAvEn=-; 03-21-2016 at 10:15 AM.
Thanks for the detailed cylinder head shots. You've got some major exhaust valve seat recession, especially in 1A and 3A. The seats should be replaced. Intake seats look good.
Yeah, the exhaust side looks a bit recessed, I was not too surprised though. All of the intake side looked good. Everything is at the machine shop now, should have an idea of east needs to be done to everything early next week. Can hardly wait.
You'd think huh..... Don't want their new engines though. It looks like it would have gone a lot longer. The cause for the rebuild was low compression. The oil rings were stuck, possibly caused by my long (20k+) oil change interval. Everything else is looking great. I can't wait to hear what the machine shop finds out.
You'd think huh..... Don't want their new engines though. It looks like it would have gone a lot longer. The cause for the rebuild was low compression. The oil rings were stuck, possibly caused by my long (20k+) oil change interval. Everything else is looking great. I can't wait to hear what the machine shop finds out.
Nik
What oil did you use on your 20,000 miles oil change intervals? I don't see a 2nd gen or 3rd gen for that matter hitting anywhere near 365,000 miles even with 5000 mile oil change intervals.
Dammit!
Appears my head is dead. Every cylinder has a crack between the spark plug and a valve......Said its from chamber temps, not overheating. Anyone have any thoughts on this?
Everything else is looking really good, going to have the cylinders done +20
Nik
Dead Head :(
Last edited by -=gRaY rAvEn=-; 03-21-2016 at 10:17 AM.
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This is the first time I heard of all four cylinders having cracks, running lean perhaps. I have been reading a thread which I'll look up for you later about someone who tested the Tritec engines and made informative statements about chamber temperatures and EGTs, quite an interesting read.
Well, that's a bummer. Not a huge surprise though. Aluminum doesn't have an infinite life when stress cycled. In engineering lingo, the S-N curve doesn't have an asymptote. IOW, put it through enough stress cycles and it will eventually break, even when those stresses are low. It's the same reason that airplanes are only allowed a certain number of landings and flight hours.
It looks like the crack didn't progress into the water jacket which is good (your combustion chamber would have been spotless if it had) and you'd have noticed a loss of coolant.
02-08-2016, 10:53 AM
