to buy new pistons and bearings or not

[johnk]

Looking for some direction on this decision

My 280sl is completely apart and in the reassembly stage with only 82,000 miles on it. While the pistons and bearings seem to have a lot of wear left, the rings probably have only 20,000 miles left on them. A member who's knowledge we all respect mentioned that while I could just hone the cylinders and replace the rings, a lot of members had problems with jsut replacing the rings. Another member that I highly respect replaced just the rings on his and hasn't had any problems after 10,000 miles or so.

So I took my block to a reputable machine shop and thought I would just rely on his recomendation after he measure everything. Well that was back in June and he is finally gettign to it, and I am a bit concerned he may say just replace the rings just to reduce his back log quicker.

The incremental cost of new pistons and bearings is about $2,300 plus machining. Currently Budsbenz is the only place I can find 1st repair pistons ($1,800) other than the $137 Mehle pistons that seem to pop up everywhere. I could go with just the rings now, but even if they work perfectly I or my son will end up needing to overhaul the engine in fifteen years or so and who knows what the availability or cost will be then.

Anywas I appreciate any insight or past experience wiht the similar issue.

Thanks gents
John

[stickandrudderman]

A good machine shop should be able to provide you with hard data as to the wear on the cylinders and that data alone determines whether a rebore is required or not.
If not then new rings and a hone will be fine but have you actually got a set of rings to fit?

[Benz Dr.]

All good questions but you also need to measure your pistons and see how well new rings will fit into the grooves. Any excess play in this area and you will need new pistons.

[Shvegel]

Deves Rings.  They will make up a set to your thickness, bore, etc. 

[Benz Dr.]

Getting new rings isn't a problem. If the grooves are worn then you do have a problem. New rings won't fix that.

[johnk]

Dan
Which grooves are you taking about? The cross hatching in the cylinders?

[Benz Dr.]

No. The ones on the pistons where the rings are fitted.

[johnk]

Gotcha makes sense

Thanks dan

[SEB]

I am the first day here as a junior member. So I do know the habits, navigation etc. so sorry. I am also not an Engineer or Technician, but old Mercedes are my hobby and passion since years. And may be I can give you a suggestion. Few years ago I rebuild in my W111 Coupe the engine like above described with new pistons, rings etc ( it was expensive), but now I have rebuild an engine in other way, where are implemented bushes.  If I used the correct English word. Not every body can make this. If you can implement the bushes- In this case you can use the old pistons, new rings and in the future you change only the bushes and rings and do not degrade the engine.
So only a suggestion. May be is possible in your case?

[DaveB]

Hi Sebastian,
'Bushes' is correct but 'sleeves' or 'liners' are more common terms.

[MikeSimon]

I am sure Sebastian is talking about "sleeving" the block - which is quite a job on a SL motor.
I think the whole issue is pretty straightforward. If the bores are OK and within the service limits, just use new rings. If not, an overbore and new pistons are in order.
I don't know, though, why an engine will need new rings at 100,000. Maybe "preventive maintenance" is the key word here.
I would definitely not touch the crank and put new bearings in it, if there isn't a problem.

[johnk]

Thanks gents. Seems like the general recommendation is to just replace the rings if everything measures up.  I think that is what I will do if the engine shop finds everything else in line.

[SEB]

Hi John,
many thanks for this explanation. As you can imagine I am not yet so familiar with such words in English.

What I wonted to suggest is, that few years ago when I made my W111 Coupe it was told to me, that the sleeving is not possible in such engine. But now I have an other shop near Berlin, who has this know-how and tools.  I am convinced  to this solution. Especially in case, when you do not get the necessary pistons on the market, not mentioning the incredible prices for the pistons. And how is the experience with the sleeving of  M180 Engines family in the US?

[Benz Dr.]

I wouldn't be so inclined to sleeve a good block. One damaged cylinder I might do, but not all six unless I couldn't find anything else. I would bore to maximum oversize if needed and then look for another block if I had to after that point. I'm not so sure you can sleeve a 280 block.

[MikeSimon]

The late 280s, M130-983s are probably impossible to sleeve due to the cooling slots between the cylinders. There is hardly any material left.
look at the upper part in the picture. Although this is an oversize bore, there is very little wall.

[johnk]

Ok so my decision has been made for me. The machine shop finally called back and explained why the cylinders didn't have much of a lip yet the rings were worn. Someone has already been "in there" as he said and the cylinder walls are at different sizes. He got .33 max wear so I am going with 1st repair pistons.

Are the Mehle pistons ok? They seem to be all that is available when you can find them.

He didn't measure the crank yet but said he can get the bearings cheaper than I can.

John

[Cees Klumper]

If you mean Mahle then AFAIK these are perfectly fine for our cars and might have even been original equipment, alongside I think Kolbenschmidt. Just saw in Europe they cost around €140 each for the 280SL.

[johnk]

If you mean Mahle then AFAIK these are perfectly fine for our cars and might have even been original equipment, alongside I think Kolbenschmidt. Just saw in Europe they cost around €140 each for the 280SL.

Thanks Cees. Where did you see these for that price in Europe? The SLS shop is 229 pounds each which probably translates to close the the $300 US that Buds wants by the time you get them here.

Thanks
John

[Cees Klumper]

I googled 'Mahle kolben' and found sites that sell them in Germany:

https://m.autodoc.de/autoteile/kolben-10629/mf-mahle-original

They list Mercedes Pagode and then by type (230, 250, 280).

In your original post you were referring to $137 pistons from Mehle, these are actually Mahle pistons. Autohaus
Az carries them. That price includes rings and wrist pin it seems

[johnk]

Thanks Cees and you are right. I should have noted the autohous pistons in my last post. When I first started this process I didn't know who Mahle was and I was suspicious of them as their pistons seemed so cheap and available. What I found out since them is they were one of the OEM suppliers, but all of the affordable pistons offered are 2nd repair. They must have an adequate supply of that size.

I will follow you link to see if they have 1st repairs available.

Thanks for your help with this.
John