I was told by several good people that you have to resleeve a block and replace the psitons with oversize pistons once you pull the pistons because the block bores wear in an oval fashion. It makes no sense just to pop new piston rings on there. Is this true? I am rebuilding a Diesel with Mercedes shop forum help right now.

On my 240D I didnt resleeve and I used Deves rings ant a year later it blew oil like crazy. On my Volvo diesel rebuild I lost no oil.

resleeve yes new pistons not necessarily.depends on original piston condition.any good rebuilder would be able to measure and advise.dont recommend the old "berlin rebuild" that being rings only.i did this on an old volvo(vw) diesel.it worked well but the engine was noisy.

Berlin rebuild.
Who cares if'd be noisy, these cars are noisy anyway.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

"was told by several good people that you have to resleeve a block and replace the pistons with oversize pistons "

The economic value to a system where you can resleeve the block is that if you have well made pistons... then you go back to original sleeve size and reuse the pistons...

This is particularly important with the Turbo Mercedes because the pistons are so expensive.

The sleeves are only about $35 dollars Each... pistons for a 5 cyl can run $1000...

So new sleeves bored to match your piston, and new rings (even special one from Deves to compensate for ring land wear ) is the sweet point for doing it right and at reasonable cost.

I thought about this before I jumped and went new pistons (stock, not oversize) and new sleeves. The sleeves need to be precision bored and honed. I pressed the sleeves out and in myself with a tool I made, and cut down the tops of the sleeves to match the block deck. If your pistons are OK, you are in luck, but mine weren't. Deves makes a special set with overwidth top rings, but my ring lands were too worn on the second groove also. The last I talked to them I suggested that they consider making a set with 2 wider ring sizes as there would be a market for it. I got my set of Mahle pistons and rings from Rusty for $675 but the prices on those have gone up a LOT since then. Carrameow, I know you can do it, but that motor is a lot of work. Good, used engines take less time.......

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

If the cylinders mic out within spec, replacing the rings would be acceptable. The likelihood of that being the case on one of these engines is probably wishful thinking.

Secondly, if cylinders do indeed need attention, you don't HAVE to replace the liners, you can bore the liners to an oversize just as you would with any engine then use oversize pistons.

The other option would be to resleeve which must be done by a machine shop. They replace the sleeves, cut the top with a boring bar and then finish to size if necessary, then reuse the original pistons. This is my least favorite approach. Although it is typically the least expensive, you are reusing the second most highly stressed part in the engine, the piston.

My $0.02,