Okay, here is the situation.

My mom recently got a recall on her 2001 BMW M3. To my suprise the recall included new rods, bearings, and rod bolts. That is pretty major for a recall. My brother was the one who took the car in for service and they told him there that he needed to break in the "fresh" motor for 1200 miles.

My understanding of engine break in is that the only thing really needed to be broken in are the piston rings. I didnt think bearings were a break in issue.

NOTE While typing this I realized that if you wanted to change the rods you would most likely have to take out the pistons to get to the wrist pin. New rings were not listed in the report they gave us that detailed what they did.

What do you guys think they did about the rings? Do you think they added new ones or re-used ones that were already in there? (is it even possible to re-use rings?) or do you think its possible to remove the wrist pin without removing the piston?
Just curious

 

it would be stupid to reuse the rings...and they didnt, thats why the break in.
to change the rod, the had to take the pistons out; hone and new rings

 

I believe they did reuse the rings. I don't think they honed the cylinders either. There was most likely a metallurgy issue with the rods, calling for their replacement. Rod bolts are not generally reuseable once they are pressed out, so they were replaced as well. Also the bearings have established a wear pattern with the rod big end and crank journal, so the clearances might not have been perfect if they were reused. I believe the reason for the 1200 mile break-in is to allow the bearings to "wear in" to the crank, greatly reducing the chance for a spun bearing. I work with a retired BMW master mechanic, so I will confirm everything tomorrow.

 

well, that would suck since they would have to make another recall for ''burning oil'' then.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jim Truett &raquo;</TD></TR><TR><TD CLASS="quote"> I work with a retired BMW master mechanic, so I will confirm everything tomorrow.</TD></TR></TABLE>

I would appriciate that a lot

 

I cant see BMW reusing piston rings, but i guess it depends on the dealer.
Im sure they replaced the headgasket too, but thats probably not on the list
of repairs either i would guess. Maybe call them and confirm. Only real way to find out.

 

Wow,i didnt know rod bearings had to be broken in.Or maybe that is just with beemers

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mmuller &raquo;</TD></TR><TR><TD CLASS="quote">well, that would suck since they would have to make another recall for ''burning oil'' then.</TD></TR></TABLE>

Why?

Just because you remove the piston from the bore doesn't mean the rings will not seal when reinstalled. You simply need to remove any carbon buildup or ridge from the upper portion of the cylinder so you don't damage the rings upon disassembly. They move when the engine is running anyway, so indexing them is not an issue. Just put the pistons back in the cylinder they came from.

Recall Update:
After discussing the issue with a BMW master mechanic it seems there are two recalls concerning rod bearings on the M3. Both recalls are currently open, and the most current is required to remedy a problem with the bearings installed in the first recall. I was told the second recall requires replacement of the bearings only. Depending on the vin number and previous updates, you may not require the second update.

The piston rings are not replaced, and the cylinder walls are not honed for this service. They do not have problems with vehicles returning with oil consumption issues.

 

reusing rings could cut longevity of the car, even using putting them is the same cyl.; they could cause the cyl. walls to glaze over and not re-seat properly.
Its something that i thought bmw would address, but guess not
but oh well...