Anyone ever see this before?

[jjs3rd914]

Anyone ever seen this before, if so what happened?

We are rebuilding a 1972 1.7L. Look at the condition of the removed flywheel main bearing, the one that is suppose to set the crank end play. The new bearing with the trust surface is also shown. What is amazing in the car ran great and there was no noticeable indications of any issues. It almost looks as it someone had machined off the rear flange. The crank end play must have been huge! We did not see any chunks of metal when the case was split. We suspect the machining has been going on for quite some time and the filter was capturing the debris.

It also appears that the #3,#4 main bearing webs in the case were in part of acting as the thrust surface with the crank throws slightly machining the webs.

Another thing we found was the clutch TO bearing was missing both of the curved plastic end spacers. The bearing must have been floating back and forth in the fork. There was no evidence they were ever installed the last time the motor was out as no remnants were found inside the bell housing. We have only driven this car a few hundred miles since purchase. We wonder if the fact these were missing contributed to the disintegration of the main bearing.

Anyone have any thought as to what happened here? It does not look like there is any permanent damage although as expected the flywheel side of the rear bearing race is chewed up a little but the new bearing fits snug. Would someone have purposely machine off the bearing flange? If so what for?

Thanks

Jeff

[seventythree]

What about the shims? How many and what thickness, and what condition?

[jjs3rd914]

More information, there were only two shims found, each .011" thick (.022" total). The shim closest to the crank was rolled to a certain extent inward towards the crank bearing or what was left of it. Again no remnants of the expected third shim were found.

We are at a loss to explain what happened and what to do to prevent from happening again.

Thanks

Jeff

[seventythree]

With one shim missing and the outside lip of the thrust bearing completely gone, how much endplay did you have in the crank?

Also, the dowel pin hole on the old bearing appears to be somewhat elongated (oval shaped). Is that true or just an optical elusion?

I had a problem with the thrust bearing on my 2.0L once, which I believe was the result of inadequate bearing pinch. But the end result was different than what you are seeing here.

[Dave at Pelican Parts]

My guess is that someone decided to replace the flywheel when they replaced the clutch, and never bothered to check the endplay.

My own car ran for several years with ever-increasing endplay. (Back at least 2 POs, in fact, and for a couple of years after I bought it!) I had dropped the engine for unrelated reasons and was trying to figure out why the whole fan/crank/flywheel assembly moved fore-and-aft when I spun it to adjust the valves.

I figured out that there was about 1/8" of end-play. Three shims in place, but the thrust flange on the main bearing was worn down to tinfoil-type thickness. The webs in the case had been worn a little, though probably not even as much as yours appear to have been.

The case needed align-boring (unusual for a 914 crankcase!) and oversize bearings. The latter, BTW, seem to be a little tough to find.

--DD

[jjs3rd914]

Good eye SeventyThree! I checked the old bearing and indeed the retainer pin hole is elongated. So is the case at that point but only very little. I did a stupid thing by not measuring the end play before disassembly, but it had to be close to an 1/8".

Supposedly the motor had been rebuilt around 10K ago so I guess we assumed all was okay. At the last minute we decided to freshen the motor while it is out while doing some longitudinal repair. Good thing, for who knows how much more damage could have been done or how long it would have lasted.

Regarding Dave's comments. He may have nailed it with speculating the replacement of the clutch and flywheel and no one ever checking end play. I keep going back to the fact there were no plastic spacers on the clutch fork centering the TO bearing allowing it to freely float back and forth and what that may have contributed. Put all this together and maybe that is the answer.

Question to Dave? Should I now be concerned about line boring the case. The crank was near perfect and the case looks good except for the unwanted machining of the webs. We just had the crank polished and will put in new standard bearings (which were hard to find). How would I know if it needed it with only normal home measuring equipment? What else should I be concerned with? We are ready to reassemble.

Anyone else have any theories?

Thanks to all.

Jeff

[Dave at Pelican Parts]

I don't know how you'd check with only normal home measuring equipment. In fact, I don't know how align-bore is really checked... I think the Wilson book ("How to Rebuild Your Volkswagen Air-Cooled Engine") has information on how the machine shop does it, but I haven't heard of a shadetree method.

You might want to check with your machinist and see what just that one check will cost.

--DD

[seventythree]

In my opinion, bearing pinch is absolutely critical for bottom end longevity. This could be easily compromised with an improper align bore. So, if you don't need it, don't do it. A qualified machine shop will use a specialty gage to check the case.

The problem is, with proper pinch, why was the thrust bearing sliding back and forth to cause the elongation of the retainer pin hole?

Also, with any shims in place, and properly lubricated, why would the thrust bearing wear the way it did?

I think it is more prudent to investigate and find these answers before putting the bottom end back together. After all, you don't want to be doing this again and again.

Post this over on the Rennlist. There are a couple of individuals there whose input you may appreciate.

[AL MEREDITH]

I just had a similar problem. Bought a 912E (2.0L TY4 engine) which the PO said had been rebuilt 10K ago. Leaking VERY bad from rear seal. Easy fix, pull engine, remove flywheel, and replace seal. The seal was hard, like plastic, and one of the three shims was all beat to hell. Then my son took a screwdriver to the rear bearing and it rotated about 15 Deg. I put that engine on a shelve and built another ( Jake Raby 2056) End play is important. I think the book says .004-.006 I always set a little loose ie: .006. AL

[galto]

End play is a very critical issues, it effects wear of the crank, throw out bearing, clutch tyranny gears, and the most important, the way that the thick/thin film lubrication works. I wouldn't advise for setting it loose. Set it exactly in the middle if you can. The tolerance is in there so the assembler at the factory doesn't waste a whole day looking for just the right shim.

Checking bore on a hole that big is a pain. That's all there is to it. I use one of two methods:
1.) use a large hole guage with a long extension, put it down there, square it up and then remove it to measure what the hole was.
2.) Use the right automated tool that you insert and it has little feeler arms that report back how much they move. (Works kinda like a dial guage, but with the spindle 90 to the readout.

You _could_ set some clay in the bores, torque the case to spec and measure the results... but it's slightly better than guessing.

The quick and dirty method I have used once, with mild success is placing multiple plastiguage around the crank (0 45 180 225) from then assuming the crank was round, and at the given dimension then extrapolating what the round out was. Again, don't think this is very good either.

Unless you want an expensive specialty tool that you probably won't ever use again, take it to a quality machinist and let them check it.

Ask them to torque the case to spec before they check the roundness, I would copy down the specs for them.

[jjs3rd914]

Thanks for all the replies thus far. We did spot check the crank bores the best we could and they seem to be at spec.

Also we have done a preliminary spot check on the end play. We installed 3 shims, 2 x .0126 and 1 x .0094 for a total of about .034 and we still have about .010 of end play and want a target of .003.

The manual says to install only 3 shims. Shims come in .0094, .0118, and .0126, .0134, .0142, and .0150. So it looks like we need to buy some thicker shims. Does this end play measurement seem in the ball park? It seems that we are on the high side and are going to require 2 x .015 and 1 x .0126. We are going to have to get 2 of the .015 shims unless it is permissible to use 4 shims. Any thoughts?

Thanks to all for helping unravel this mystery.

Jeff