Rings,crank and rod bearings for the 240? - PeachParts Mercedes-Benz Forum

Matt Laube · #1 01-31-2010, 08:38 PM

I have a smoky oil burning 240. My MB trained friend said early 80's had oil control ring problems. I have rebuilt many auto,tractor and motorcycle engines but no MB diesels. Anything to look out for?

Do these engines have sleeves? If not how about out of round bores? BMW small sixes had many #6 bore out of spec....But hey that's a BMW.

I have a great 5 cyl engine that would drop in...but I didn't want to go to the auto trans/make the conversion route and sacrifice my fuel economy.

kerry · #2 01-31-2010, 08:42 PM

The thing to watch out for is your wallet. A used engine would be much cheaper. No oil control ring problems that I've ever heard of.

bmwpowere36m3 · #3 01-31-2010, 10:35 PM

Considering the cost of re-ring, sleeving, and machining you'll easily be at 1k including an engine seal kit (not including pistons, bearings, or crank work). I would just drop in the 5 cylinder motor...

mplafleur · #4 01-31-2010, 11:13 PM

You don't need to resleeve. There are 1st os, 2nd os, and even 3rd os pistons and rings available. I've done 1st oversize on a 240 and it runs great. I did get a good deal on the piston set on eBay. $100 or something like that.

You could probable re-ring it at 1st oversize and get the sleeves bored out to match.

My machining cost less than $100.

Stevo · #5 02-01-2010, 09:40 AM

If you re sleeve you must have the cylinders bored for the new pistons anyway so, if you can get away with it, buy over size pistons and bore to fit. I rebuilt a couple of these engines (and they are still alive) so it doesn't take a "master" mechanic, after all they were designed to be worked on in a tent in the desert

JEBalles · #6 02-01-2010, 09:48 AM

If you rebore it and use oversize pistons, can the block no longer be re-sleeved?

leathermang · #7 02-01-2010, 09:56 AM

I do not know how many of you people have actually honed a bore or rebored a cylinder bore .... whether a newly installed which needs to be fitted to the piston going into it ( the MB method ) or tried to take out out of round and taper from a bore which is not being resleeved...
but I have done some of this and the machinery it takes to do it correctly... and the extreme number of exact measurements which need to be taken while doing it take away all the supposed advantage some think might exist with trying to rebore the old sleeves..
Reboring is very different from Honing to fit the piston to the bore..
different equipment...
The things you will have to do to do the reboring of the old sleeves... is way more than half what it takes to do to newly installed sleeves... which only require honing to fit...
I suggest that before anyone puts any money into one of these decisions that they get the paper copy of the Factory Shop Manual and read it front to back...

Shawn T. W. · #8 02-01-2010, 10:04 AM

Also something to think about . . . is are you sure it is the rings?

The valve guide seals also cause smoky oil consumption . . .

Stevo · #9 02-01-2010, 10:30 AM

Quote:

Originally Posted by leathermang

I do not know how many of you people have actually honed a bore or rebored a cylinder bore .... whether a newly installed which needs to be fitted to the piston going into it ( the MB method ) or tried to take out out of round and taper from a bore which is not being resleeved...
but I have done some of this and the machinery it takes to do it correctly... and the extreme number of exact measurements which need to be taken while doing it take away all the supposed advantage some think might exist with trying to rebore the old sleeves..
Reboring is very different from Honing to fit the piston to the bore..
different equipment...
The things you will have to do to do the reboring of the old sleeves... is way more than half what it takes to do to newly installed sleeves... which only require honing to fit...
I suggest that before anyone puts any money into one of these decisions that they get the paper copy of the Factory Shop Manual and read it front to back...

You are saying that new sleeves only have to be honed to fit new pistons?

leathermang · #10 02-01-2010, 10:46 AM

MB sleeves have to be honed ( according to the FSM ) to fit whatever piston is being put into them.
They come undersize to ' allow' or ' require' that whichever way you want to look at it..

Even if they happen to fit the piston you have scheduled to put into that bore I think you are required to hone with round stones to get the break in finish correct... something you have to stop regular honing slightly short of to keep from going past the correct tolerances...

Steve, I am not sure I read your question correctly.. are you imagining some situation where oversize pistons were in the car and are now worn so they might fit new stock size sleeves ... or some combo like that ?

Stevo · #11 02-01-2010, 01:49 PM

Quote:

Originally Posted by leathermang

MB sleeves have to be honed ( according to the FSM ) to fit whatever piston is being put into them.
They come undersize to ' allow' or ' require' that whichever way you want to look at it..

Even if they happen to fit the piston you have scheduled to put into that bore I think you are required to hone with round stones to get the break in finish correct... something you have to stop regular honing slightly short of to keep from going past the correct tolerances...

Steve, I am not sure I read your question correctly.. are you imagining some situation where oversize pistons were in the car and are now worn so they might fit new stock size sleeves ... or some combo like that ?

The engine (1980)I rebuild for my 79 I had it re sleeved then bored for over sized pistons, figured I wouldn't live long enough to need to rebuild it again

The next one I did I just had it bored for O/S pistons as it was with in spic. I wouldn't "skimp" on pistons for a 616, they are relatively cheap.

bmwpowere36m3 · #12 02-01-2010, 02:26 PM

Quote:

Originally Posted by mplafleur

You don't need to resleeve. There are 1st os, 2nd os, and even 3rd os pistons and rings available. I've done 1st oversize on a 240 and it runs great. I did get a good deal on the piston set on eBay. $100 or something like that.

You could probable re-ring it at 1st oversize and get the sleeves bored out to match.

My machining cost less than $100.

Pistons are the most expensive pieces here, $200+ a piece new. Obviously if you find a used set your taking a chance and saving considerable money. However you do not want to re-ring a piston with O/S rings if the piston isn't O/S. Short of just re-ringing the current pistons (as long as they are good and the cylinder isn't worn or out of round), the next cheapest it reusing your pistons, re-ringing, and sleeving.

leathermang · #13 02-01-2010, 03:25 PM

Deves is the company I was trying to think of...

Deves.com
240 D, OM 616, Diesel 1978- 4 90.90 3.00 2.00 4.00 - - - 1964 B
3.579 1-K 1-SK 1-O

1964 B $119.00

Stevo · #14 02-01-2010, 03:28 PM

So does the sleeve need boring or just honing, when installing new pistons? and what about the slightly different spic size on #1. Not having the new sleeves bored would have save some $.

leathermang · #15 02-01-2010, 03:31 PM

A new sleeve only needs honing....
The different size on number one is very important....
it often causes problems for people doing this work without the FSM to go by...
Each sleeve is supposed to be honed for the EXACT same piston which is going to be inside it... and lots of exact measurements are supposed to be taken first....