617 piston damage - PeachParts Mercedes-Benz Forum

mach0415 · #1 02-23-2011, 08:50 PM

So I posted some info on another SD that I bought. It had a dead cylinder 3. Thanks to all who posted info on getting the TC guide rail pin out. I removed the head today and found in pristine shape. This engine has no timing chain stretch-maybe 1 degree. I found the #3 piston broken at the top and you can see about 1 inch of the upper compression ring land circumference exposed, but the ring piece is gone. The bore is smeared with aluminum in spots. It is hard to tell if there are scratches at this point. I will pull the piston next to see the full extent of the damage. So, what causes this kind of damage? Also, is there anyone who has had good luck replacing only the affected piston after cleaning up the bore? An engine builder friend of mine told me he takes muriatic acid to remove the aluminum smear. What are your suggestions. Pics to come.

layback40 · #2 02-23-2011, 08:56 PM

Hey Mark,
konstan did a rebuild not that long ago, he had one bad piston. He honed the bore & used a second hand piston. He has a couple of very long threads about his project. Worth a read.
Good Luck !!!

leathermang · #3 02-23-2011, 09:01 PM

MB pistons are measured... then the New sleeve you installed in the block is bored TO FIT that piston...
IF done according to the FSM you can be in good shape going forward..
as long as you determine what caused your problem in the first place so it does not repeat...

mach0415 · #4 02-23-2011, 09:01 PM

Thanks. I am going to see what he talks about. I honestly think I can get away with it, based on what I see so far. DO you have a link to the reference? Also, is this a symptom of ether use? or Was there just a weak spot somewhere?

leathermang · #5 02-23-2011, 09:05 PM

You need to be looking for a Factory Shop Manual for your engine....

mach0415 · #6 02-23-2011, 09:16 PM

Thanks. I am debating doing a swap with a good used engine, b/c I am not in a position to drop $3,000 on rebuilding an engine to go into a $1,800 car.

vstech · #7 02-23-2011, 10:01 PM

Quote:

Originally Posted by mach0415

So I posted some info on another SD that I bought. It had a dead cylinder 3. Thanks to all who posted info on getting the TC guide rail pin out. I removed the head today and found in pristine shape. This engine has no timing chain stretch-maybe 1 degree. I found the #3 piston broken at the top and you can see about 1 inch of the upper compression ring land circumference exposed, but the ring piece is gone. The bore is smeared with aluminum in spots. It is hard to tell if there are scratches at this point. I will pull the piston next to see the full extent of the damage. So, what causes this kind of damage? Also, is there anyone who has had good luck replacing only the affected piston after cleaning up the bore? An engine builder friend of mine told me he takes muriatic acid to remove the aluminum smear. What are your suggestions. Pics to come.

ether?

layback40 · #8 02-23-2011, 10:06 PM

Mark,
If you search for threads by konstan, you will find them. Maybe worth a PM to him, he can give you the lowdown on how the car is now going. He did complete set of rings & bearings.
If that bore would clean up & you could get some one on here to sell you a good piston, maybe you could get it going very cheap. Probably would be better replacing all rings & bearing shells.

leathermang · #9 02-23-2011, 10:20 PM

Quote:

Originally Posted by layback40

Mark,
If you search for threads by konstan, you will find them. Maybe worth a PM to him, he can give you the lowdown on how the car is now going. He did complete set of rings & bearings.
If that bore would clean up & you could get some one on here to sell you a good piston, maybe you could get it going very cheap. Probably would be better replacing all rings & bearing shells.

MB Factory Shop Manual does not suggest that a bore can be ' cleaned up' .. and since it is easy to pull the sleeve and put a new one in...that should be the recommended procedure... the chances a used bore can be cleaned up to the extent that it would pass the MB specs for installing a new or used piston are very very slight... perhaps bordering on fantasy....

vstech · #10 02-23-2011, 10:28 PM

that depends on the damage done. if the original hone marks are intact, my FSM states cleaning and installing a new piston can be done.

leathermang · #11 02-23-2011, 10:58 PM

Quote:

Originally Posted by vstech

that depends on the damage done. if the original hone marks are intact, my FSM states cleaning and installing a new piston can be done.

I was playing the odds given the description of something wiped off the piston onto the wall of the bore.....
Once you are torn down that far... I suspect installing new sleeve would eliminate a lot of labor and questions...

DeliveryValve · #12 02-24-2011, 12:23 AM

Quote:

Originally Posted by leathermang

MB Factory Shop Manual does not suggest that a bore can be ' cleaned up' .. and since it is easy to pull the sleeve and put a new one in...that should be the recommended procedure... the chances a used bore can be cleaned up to the extent that it would pass the MB specs for installing a new or used piston are very very slight... perhaps bordering on fantasy....

I wouldn't call it bordering on fantasy. It is totally possible if conditions are right. If you originally have a group 0 piston and a start with a bore size of 90.898 with no severe scoring, a clean up hone can take off as much as .030mm and be still within spec of a used/new group 2 piston.

.

layback40 · #13 02-24-2011, 12:43 AM

I know of a member on here with a cleaned up bore & a second hand fitted piston. If you want a reco motor then go with new, if you want a motor that runs with out a huge expense go with what I suggested. Or just fit a second hand motor.

leathermang · #14 02-24-2011, 01:23 AM

Quote:

Originally Posted by layback40

I know of a member on here with a cleaned up bore & a second hand fitted piston. If you want a reco motor then go with new, if you want a motor that runs with out a huge expense go with what I suggested. Or just fit a second hand motor.

Most people do not have the measuring devices for proper determination of whether the bore is ' go or no go' with regards to ' clean up' ...
New sleeve is cheap and you have a trusted place to start.. which can be done with patience and a three blade honing tool....since you would not be trying to correct anything except the bore diameter... but the other factors in a used bore would probably require a four blade boring stones tool...and the idea of it being bored true to the centerline of the crank.... back to that ' very unlikely' situation...

layback40 · #15 02-24-2011, 03:20 AM

I do agree with you leathermang.
It is always best to put things proper & right. If it was one of my machines that I make a living from I would be doing a rebuild.
Mark appears to want to get the car going reliably for as little $$ as possible. He doesnt appear to be wanting to do a full restoration or rebuild. That is why I have suggested that he may be lucky & get by with a hone / second hand piston / rings. He may be able to do that for under $200 in parts if he only rings that cylinder.
Heck its number 3, I suspect you could do it with out removing the motor from the car.
There is always a risk associated with that. He probably should inspect all 5 pistons out of the motor. I cant recall if he did a compression / leak down test. If the motor goes back together & runs ok, its a win !!