Where to find oversize pistons?

I am in the process to remove the enfine from the van and I need some oversize pistons and rings for a OM642.

Is there a supplier for the piston if I go to the first oversize or do I just install it on the STD piston?

Thanks

No oversize pistons available I am afraid.
You need to buy a block and matched pistons; better still buy an exchange engine at $10,600 exchange..
Fit and forget its under the hood for the next 100,000 miles.
Dennis`

I'm pretty sure that the engine has some sort of fancy coating on the cylinder walls- the cylinders are not sleeved.

In short, the engine is not rebuildable.

Confirm a coating like Nicasil or Alusil.
Basically a series of silicon alloy rods arranged in the cylinder on production and electrically charged in the block. This in turn makes them melt a uniform manner & fuse to the cylinder bore.
Dennis

OK, so why Mahle / Clevite sell oversize rings then? It is the same fabrication system as the 2.7l?

It may not be cost effective with Sprinters but many engine rebuilders build up and grind cranks and cam. Same goes for cyclinder reconditioning.

http://www.powersealusa.com/prices/

http://www.langcourt.com/page26.html

This hash been hashed and rehashed ......engine rebuild is a lost art for many reasons, parts costs , labor cost, crate engines, factory short and long blocks and aftermarket in factory rebuilding.

Parts pricing is the real issue with other manufactures ......example head rebuilding with variable twin cams, 3 or 4 valve per cyclinder, difficult valve guide service, valve seat work.....make the factory head assembly a bargain.

The idea of in-shop engine rebuilding has kind of become a victim of modern materials technology and design. In these days with electroplated bores, advanced piston alloys, CAD design simulations, etc., it's become common for engines to live to a very long service life (perhaps their entire practical life) with no disassembly. In that environment it just isn't very cost effective to maintain a parts supply chain, machining techniques, training, etc. for in-the-field rebuilds because there just isn't as much business as there used to be. If the need for internal engine work exists at all a fully remanufactured engine is the way to go. This does leave someone the occasional low-miles failure in the lurch, but that situation just isn't common enough these days to support a cost-effective repair option.

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lindenengineering said:

Confirm a coating like Nicasil or Alusil.
Basically a series of silicon alloy rods arranged in the cylinder on production and electrically charged in the block. This in turn makes them melt a uniform manner & fuse to the cylinder bore.
Dennis

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That's how they do that! Never had a clue

Bobmirko said:

OK, so why Mahle / Clevite sell oversize rings then? It is the same fabrication system as the 2.7l?

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So it might be but you are not comparing eggs to eggs.
The 2.7 litre engine is old style iron block design, the later V6 is newer generation of alum/alloy block construction.
For reasons of cost introduction, thermal and load stress considerations (amongst other reasons) the alum block design can have much more uniform construction which in turn leads to potentially longer engine life.

By virtue of the design a thin yet very durable coating can be applied to the cylinder bores by electronic flash fusion techniques which has excellent heat carrying capabilities.
This thin coating is about 0.010" thick or (0,025mm). Any attempts to bore it out to a new hole size would redoubtably mean breaking though the coating to the relatively rough parent block or leaving the section so thin that it would simply strip off in service with catastrophic results.

So some pundits might say well make up some cylinder liners and press those in!
OK!
To get the same heat propagation through the new liners as the fused original what would be the interference requirement need to be?

From my experience & engineering dictum it would need to be in the order of 0,004" or 0,01mm.
To get that level of interference "fit" on an alum block there would need to be a lot of heating of the structure to allow a scuff free install and even then using an industrial lube medium like Castrol Illoform would not entirely ensure a uniform fit. Even the activity of heating the block and pressing in of liners would no doubt cause block structure deformation and cracking risks.
That in turn would lead to high block scrappage on repair or high risks of in service engine failure.

I find it frankly hard to reason with this old fashioned lingering idea that today's engines can be reconstructed.
Many if not all cannot, and the trend has been around for a long time now. BMW have the distinction of introducing it (fused cylinder coatings) in their 7 series 4.4 litre V8 in the mid 90's, and its been commonplace with Asian manufacturers for about the same time if not longer.
MB has just caught up with the rat pack with the OM647.

Really those owners who buy this stuff in the "gah gah" moments at the point of purchase rarely ask what are the cost implications of ownership and service maintenance costs.
Need I state it is incumbent upon all buyers of vehicles (the 906 included) to know the service costs and ask yourself whether you can afford to own the rig and repair it when it goes 'bang" !
It called risk management!
Cheers Dennis

I have always been under the impression that the diesel engines common to Sprinter and Saloon models be uncoated bores. There are several engine remanufacturers offering normal and line reboring of these older blocks especially the EU 2.2 4cyl version, as well as bore 'hones' that if coated would destroy the surface. These will mate with, for example Mahle Oversize Alloy piston and ring sets. However Dennis is pretty much correct of later stuff, namely the V6 Blutetec (circa 2014) that now uses a steel piston for higher tolerance bore clearances with what MB call Nanosilde coating on the liner. Together these work to improve manufacturing/running tolerances and reading between the lines maybe even be paving the way to higher maximum cylinder pressures. As I understand it, this technology will be rolled out in later generations of engine as time progresses.

As far as I know - could be wrong here - there is no listed O/S shells so if your mains have spun, you need a used or new (crank) part, plus rods to consider the rebuild as viable. This info is how I am lead understand it and the basis on which I have referred others, always prepared to stand down if proved otherwise.


Edit - Dennis remember what a farce the Nicosil coating was on the XJ Petrol 90s Jags. Dissolved by petrol - what an oversight! My goodness thank god we have progressed!
All the best
Steve

Steve
Yes the Nicosyl bores were suited for fuels with low sulfur contents and BMW got their nuts in a wringer with higher sulfur in US fuels which made them corrode/fail etc.
The BMW answer was to use a different wire fusing alloy called Alusil.

Yes today due to tolerances all around it means a new engine for most manufactures when something goes phutt!
At least a good take out cheaper repair remedy !

Its afar cry today from my first rebuild at the shop where apprenticed
At 18 (1965) I had a 1925 Hispano Suiza (Wolseley Viper) engine plonked in front of me with a hole in the block, burnt valves and vital valve train drive parts missing. WTF is this monster!
With welding skills taught, with re-metalling and grinding of valves plus some good old fashioned guidance from an ex RFC retired mechanic (aero engine expert on Spad and Sopwiths) I got all tech info needed to make the valve train parts in college.

Who makes parts now?
Its like cooperage in beech wood practiced by Brits since Roman times--- almost gone! FFS
Just toss it in the trash when done.
Who needs skills I ask?
Merry Christmas & Best Regards
Dennis

My old dad was a pattern maker for an engineering shop, he later moved on to cabinet making! - The story he often told was the development engineer who kept rejecting his casting pattern for being tiny amounts over size. One day having had enough of this, he walked to the engineers office as he always did so that the hardwood component could be measured before use, dutifully standing at the desk while this measuring was carried out. The part was handed back as usual saying 'it was a few thou' over size'. Dad held it at eye level while they both peered at the surface in question. Producing a piece of sandpaper from his overall pocket my dad gave it a quick couple of passes and then puffed the dust into his face! 'There you go!' he said passing it back and exit.....

Merry Christmas from over here.
As always all the best
Steve

For your reading pleasure..........

Slide 26 of 105 mentions cast iron liner in a aluminum block:

http://aie-services-2.net/Sprinter/NV3-Sprinter_Overview_Part_2.pdf

Showkey
That last time I tried a "CUT" on these holes it didn't work.
The liner (if we can call it that) disintegrated and the block was deemed scrap.

I confess I haven't tried since as the cost and parts involved meets the cost of a new/exchange engine.

I prefer quite frankly to install an MB exchange engine and not stand the warranty issues involved for 12 months.

Its all about economic sense and liabilities of product support out of my business.
Cheers Dennis

^^^^^^^^^^^ the Economics rarely make sense. I agree many other manufacture micro finish hone cast Iron cylunder liners and no honing is done even with new rings on an old cylinder. A few manufactures are now reringing in the dealer under warranty for high oil consumption.........to control warranty cost.
Same goes for auto transmission rebuilds...........most warranty repairs are exchange only and the factory remans off site.

If the Sprinter was a higher volume seller .........the aftermarket would likely enter in the rebuild biz. They would then have work at rounds on remans cranks and blocks and economies of scale would make parts cheaper. Like the good old days when the GM rebuild kit was $400.

Hello everyone, just to confirm oversized pistons and bearings are out there. Unfortunately one size over only they are made by kolbinshmit 82.5 for the pistons if I remember correctly. We have rebuilt at least a dozen of these motors with oversize pistons and/or bearings fitted in. Out of all the motors one came back about 6 months later due to oil starvation "owner decided to do the oil change himself knocking noise right after" low/no oil dtc was stored in the ecu. Other then that no problems with oversized pistons.

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Custom MB Sprinters said:

Hello everyone, just to confirm oversized pistons and bearings are out there. Unfortunately one size over only they are made by kolbinshmit 82.5 for the pistons if I remember correctly. We have rebuilt at least a dozen of these motors with oversize pistons and/or bearings fitted in. Out of all the motors one came back about 6 months later due to oil starvation "owner decided to do the oil change himself knocking noise right after" low/no oil dtc was stored in the ecu. Other then that no problems with oversized pistons.

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Where do you bought these pistons?

You have to know someone in Germany and it takes a while to get.

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Yes, Kolbenschmidt makes over size 83.5mm. My cylinders are iron, no silicon carbide, nikasil, bore surface. Also, the brand (ARCO) in Taiwan makes a good piston for these engines. I have a set, but turns out I don't need them, as the cylinders turned out to be in excellent condition.

My engine smoked terribly, and consumed 1qt each 20 miles out the tailpipe, causing the previous owner to scrap the whole van. Using polymer oil additives, it reduced consumption down to 1qt per 80miles. Still way too much.

I believe this engine was re-ringed without honing the cylinders.
So now I am honing them before reinstall of original pistons in original bore.