Major engine damage - advice please - Page 25

jaj · 5th April 2006, 06:00

Gents

The Mercedes process that I described yesterday was from a service manual published in 1992, so it's a "full-mechanical" process, and not a chemical etch.

I have no idea how they produced the M119 engine, but it must have been laborious in those days - luckily, MB was still in the over-engineered/costs-don't-matter phase of it's existence. Only later did they drive the costs down.

Cheers
JJ

StevenZ · 5th April 2006, 06:07

Quote:

Originally Posted by ard

I just want to add a thought-

If it turns out that - when faced with this extensive explanation of honing an ALUSIL cylinder - the dealer agrees they cannot achieve that same finish, what is Mark's financial exposure? I would say that it is the $800 teardown- once the cylinder wall damage was found it should have been "game over".

(It is also not possible to spin a spring loaded hone in a cylinder and ONLY CONTACT THE BURR... it WILL contact the entire wall.)

Just didn't want you to feel 'trapped' by them- they are the experts, they should have known it was unrepairable as soon as the teardown found that- all the effort on other issues (crank, etc, etc) were wasted due to their error.

If you want to take it this way....

A

I think it is clear that the one cylinder is compromised. Is this not what Lscman has been saying? So he has 7 good cylinders and 1 that will be wearing quickly. That cylinder will develop low compression within (10K, 20K, ?) miles. Perhaps by then he can afford a new engine or we will have a rebuilder online. Or he can replace that plug frequently and live with fewer horses until ...

I don't think anyone is claiming that his engine is completely rebuilt. I'm not sure anyone has the ability to completely rebuild his engine right now. His advantage is the warranty. If the compression is low on this cylinder within the warranty period then he can say he wants a new engine - period. If his compression is still good after 2 years, then the repair worked better than we expected.

It appears that we are all going to be there eventually, or perhaps the next M5 will be the E39 M5, version 2 (unlikely). Where are us torque-hungry, manual-shifting sedan drivers to go? I think we have to keep our cars alive for a long time.

Lscman · 5th April 2006, 14:56

I believe ard is correct. A conventional hone can not be used to selectively remove a burr. Few, if any, hones are designed to remove burrs. A burr is generally a surface gouge and it's removed by taking a cylinder to oversize or insalling a sleeve or scrapping the block. I have my doubts whether this cylinder burr is actually deposition from the rod bearing....sounds far-fetched. Hones are designed to remove scuff and/or remove enough material to straighten cylinder walls, even if it's a $50K Sunnen. With good machine and appropriate stones, you can literally grind the cylinder larger and round again for an oversize piston, although machining to a significant oversize is generally done with a boring machine. A shop hone machine is generally limited to upsizing bore diameter in the 0.001" to 0.008" oversize range. Larger oversizes (0.010"+) are generally addressed using boring with finish hone.

As 6spd mentioned, MB used a mechanical polishing procedure. I am not clear about several things:

1) are MB's alusil blocks are of the exact same type as BMW which would facilitate this procedure? Any difference in the aluminum-silicone ratio or silicone characteristics or casting method or pressure or aluminum hardness could impact machining & prep measures.

2) are BMW Tech's in the shop experienced in such a service/repair process?

3) can this procedure be accurately done with the motor in the car?

4) Does the BMW network have the proper tools & training/experience/skill to properly duplicate the MB procedure? Do they even know about the procedure?

5) Is this 15 year old mechanical MB procedure adequate & proper for the high performance S62?

6) Can a "final hone" and "polish" be done while maintaining proper piston clearance? Would an oversize piston be necessary and are they available for S62? Would it be balanced well?

7) can coarse hone steps be skipped to minimize material removal and diameter change? What if skipping to the final hone step on a used cylinder does not evenly rough up the whole cylinder, therefore causing the polish to be inconsistent? Generally speaking, a used cylinder is not straight and significant honing (material removal) is needed to get a consistent finish. In these cases, issue#6 is a NO.

My guess is a couple NO's apply, which makes this fix substandard.

MAH · 5th April 2006, 15:18

First I would like to state that the engine is not on the car. In fact, almost nothing in the engine bay is in the car anymore. I have seen the engine from above and below with the cylinders #7 and #8 removed. The cylinder wall of #8 has a burr attached to it. This is not a gouge, but a piece of metal that is attached to the wall.

I will be speaking with the master mechanic today about the process being used for honing. So far, it appears that the dealer is using the best procedures available. Is this good enough? The explination from the mechanic will help and checking the pressure regularly will also give additional insight.

Mark.

Lscman · 5th April 2006, 15:50

Quote:

Originally Posted by MAH

First I would like to state that the engine is not on the car. In fact, almost nothing in the engine bay is in the car anymore. I have seen the engine from above and below with the cylinders #7 and #8 removed. The cylinder wall of #8 has a burr attached to it. This is not a gouge, but a piece of metal that is attached to the wall.

I will be speaking with the master mechanic today about the process being used for honing. So far, it appears that the dealer is using the best procedures available. Is this good enough? The explination from the mechanic will help and checking the pressure regularly will also give additional insight.

Mark.

Thanks for clarity, Mark. Good to hear the block is pulled and being serviced in a customary fashion.

If you've confirmed this is a burr that somehow attached itself to the cylinder wall, this is encouraging. I hope it did not first scrape the wall before becoming attached. If the piston skirt contacted the burr, the piston will likely be scratched & may need replaced. The piston clearances are very tight and do not leave room for burrs.

I am not doubting the efforts of the tech's or shop. I think they have been honest, fair and diligent in this effort & they may possess great skill needed to rejuvenate this marginal engine. In fact, maybe they've refinished alusil cylinders on 6 cyl cars many times with 100% success, I surely don't know! Performing this repair on a V8 is no different, aside from bore diameter and tool part#. My concern is the number of unknowns here and I don't assume things. Well...actually, I assume the worst and take steps to ensure the best (outcome).

BMWNA has put the dealership in a very difficult position & I feel for their situation. BMWNA's finanacial leveraging tactics and strong preference to repair the original hardware instead of replacing the block assembly has obligated technicians to perform complex and somewhat unusual repairs (restoring marginal stuff) where subassemblies are normally replaced (long block). Hopefully their best tech's are enjoying this challenge and putting their heart into it. If so, you might have a winner.

KBK · 5th April 2006, 16:08

Then there is the other side of the coin. Me thinks they are running out of new blocks. Which means their repair estimates based on history and intitial estimates of block lifetime/damage/etc....would/could be wrong. They might possibly be going through engines faster than they thought they would? Not a good thing.

MAH · 5th April 2006, 17:00

Quote:

Originally Posted by Lscman

Thanks for clarity, Mark. Good to hear the block is pulled and being serviced in a customary fashion.

If you've confirmed this is a burr that somehow attached itself to the cylinder wall, this is encouraging. I hope it did not first scrape the wall before becoming attached. If the piston skirt contacted the burr, the piston will likely be scratched & may need replaced. The piston clearances are very tight and do not leave room for burrs.

I am not doubting the efforts of the tech's or shop. I think they have been honest, fair and diligent in this effort & they may possess great skill needed to rejuvenate this marginal engine. In fact, maybe they've refinished alusil cylinders on 6 cyl cars many times with 100% success, I surely don't know! Performing this repair on a V8 is no different, aside from bore diameter and tool part#. My concern is the number of unknowns here and I don't assume things. Well...actually, I assume the worst and take steps to ensure the best (outcome).

BMWNA has put the dealership in a very difficult position & I feel for their situation. BMWNA's finanacial leveraging tactics and strong preference to repair the original hardware instead of replacing the block assembly has obligated technicians to perform complex and somewhat unusual repairs (restoring marginal stuff) where subassemblies are normally replaced (long block). Hopefully their best tech's are enjoying this challenge and putting their heart into it. If so, you might have a winner.

You have many good points here. I will get some more facts as to how this process is to proceed from the mechanic performing the work today and let eveyone know what the details are.

Thanks,

Mark

hudson · 5th April 2006, 22:25

Mark

With all the pessimism going on I continue to be optimistic that a quality repair can and will be done. These are NOT fly by night mechanics. They probably have more technical information then we have, and hopefully they will use it. Plus they're looking at the motor and we are guessing what it looks like (wish we had pictures).

This is my take on the “burr”. It's probably below the oil ring line on a part of the cylinder wall that does not get traveled by the piston rings only the piston skirt. So does it matter? If it were in the travel of the piston rings it would have been scraped off as the motor ran, but it didn't so that tells me that it's in a place on the wall where it really doesn’t matter. So you carefully knock the burr off and assemble the motor. Course I could be wrong.

A picture of the cylinder wall burr or the location would answer a lot of questions.

It's tough to be an armchair mechanic
Joe

DavidS · 5th April 2006, 22:48

Assuming the burr is in a harmless place, why the low compression?

(or is it just a compression measurement problem?
Or a totally unrelated problem?
Or did some other piece of bearing material scratch a cylinder? But there is no word of any scratches, just the one burr. And how can one single burr cause low compression in more than one cylinder?)

David

hudson · 5th April 2006, 23:04

Quote:

Originally Posted by DavidS

Assuming the burr is in a harmless place, why the low compression?

(or is it just a compression measurement problem?
Or a totally unrelated problem?
Or did some other piece of bearing material scratch a cylinder? But there is no word of any scratches, just the one burr. And how can one single burr cause low compression in more than one cylinder?)

David

David,

I believe it's unrelated. A good point about the burr, if it was in the ring travel you would think the cylinder wall would be scratched.

Joe