Ultimate OM642 build (2009 R320L CDI, 7G-Tronic)

[LostKiwi]

I'm sure reboring isn't a option on the 642 Engines
As they are not conventional liners.

They are steel liners cast into the block at manufacture. There are listings for +0.5mm pistons so it looks like a single rebore is permitted.
I know there can be issues with Nikasil or Alusil blocks where the pistons run direct in the aluminium.

 

[ajlsl600]

exmerctech........https://www.hemmings.com/magazine/hcc/2010/08/Engine-Lubrication/3638821.html

 

[ajlsl600]

They are steel liners cast into the block at manufacture. There are listings for +0.5mm pistons so it looks like a single rebore is permitted.
I know there can be issues with Nikasil or Alusil blocks where the pistons run direct in the aluminium.

lk.
dats same as a lot of bike engines barrels block used to be scrap when damaged ,there is a re plating recovery system now. for this block i have no idea, speak to local crank block engineers, or bike guys.

 

[ajlsl600]

Hers about the best image I can find showing it:
View attachment 40083
On the inner side of the bearing cap face you can just make out a drilling (left circle) and on the upper side a casting boss. The boss directs pressurised oil to the piston skirt and gudgeon pin.

Cooper S engines (without the offset caps) didn't have this as far as I can recall.

lk. see yr point ,thats an oldish rod ? not sure how that design would fare on worn engine when you would want all avail pressure around bearings but a DESIGNED leak it certainly is.

 

[LostKiwi]

lk. see yr point ,thats an oldish rod ? not sure how that design would fare on worn engine when you would want all avail pressure around bearings but a DESIGNED leak it certainly is.

Any oil spray to the underside of the piston or piston bores is a designed leak - its just the point where the leak occurs is different.

 

[Ge2tis]

Update time...
Sorry fellas for lack of updates, the flywheel locking tools took ages to come and when it came one of them didn't fit so luckily I had the other one on order and that one sorted everything...basically the one in the red box is not suitable for OM642

The other one is from the link below should anyone ever need it, though pricey it's definitely worth it:
https://www.xxl-automotive.de/Spezi...wenden-wie-Mercedes-112589034000::161414.html

So, after removing the pulley bolt, parts started to come again. My only concern was the discoloration of the main bearing journals however the engineer told me upon inspection that it is due to steel bearings sitting there for a long time and there is nothing to worry about...BTW the bearings were intact and haven't been spun..though they also caught some of the debris from the failed big end and were on the way of self-destruction...
The crankshaft on the other hand had passed its serviceable limits and was declared junk...
The heads however were left with an engineer. It should be thoroughly cleaned, valves reseated, new stem seals put in...basically overhauled...
I also managed to source a second hand crankshaft that is currently at CNC machinist being checked for warping and any other distortions...fingers crossed it comes back OK...
That's about it for now...
Keep tuned in...it's getting more and more interesting every day..

 

[Ge2tis]

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[Ge2tis]

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[Ge2tis]

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[Ge2tis]

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[Ge2tis]

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[Ge2tis]

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[Ge2tis]

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[KeithJG]

Hers about the best image I can find showing it:
View attachment 40083
On the inner side of the bearing cap face you can just make out a drilling (left circle) and on the upper side a casting boss. The boss directs pressurised oil to the piston skirt and gudgeon pin.

Cooper S engines (without the offset caps) didn't have this as far as I can recall.

Yes, you are correct the S model did not have this facility or type of oil squirter as the lesser A Series 848 and mini cooper models as it was based on the MG or Metro 1300 engine.

Of course these type of conrods were ok as the oil pressure on the A Series was a wacking 60psi compared with most Ford`s and i believe the OM642 engine of 40psi

Looking at all the images i would say you are on track at that mileage for a full recon.

Bores wear at the same rate as crankshaft bearings and as you have another crank i would seriously go for new pistons and that said rebore otherwise a few miles down the line more problems.

Don`t forget to wash and blow out ALL oils ways and holes to get rid of debris this includes the head`s oilways also.

What are you doing about the cams??

Don`t forget also the crankshaft shims for end play?

I think you will find that in the picture arrowed are the oil squirters differing from the Volvo 5 cylinder in which there was a separate oil gallery in the block on turbo models to enable this function.

 

[Wighty]

Welcome back ( I was worried you had been locked in the shed as you'd gone quiet ) . Glad it's all coming together .

 

[Ge2tis]

Yes, you are correct the S model did not have this facility or type of oil squirter as the lesser A Series 848 and mini cooper models as it was based on the MG or Metro 1300 engine.

Of course these type of conrods were ok as the oil pressure on the A Series was a wacking 60psi compared with most Ford`s and i believe the OM642 engine of 40psi

Looking at all the images i would say you are on track at that mileage for a full recon.

Bores wear at the same rate as crankshaft bearings and as you have another crank i would seriously go for new pistons and that said rebore otherwise a few miles down the line more problems.

Don`t forget to wash and blow out ALL oils ways and holes to get rid of debris this includes the head`s oilways also.

What are you doing about the cams??

Don`t forget also the crankshaft shims for end play?

I think you will find that in the picture arrowed are the oil squirters differing from the Volvo 5 cylinder in which there was a separate oil gallery in the block on turbo models to enable this function.

View attachment 40363

Thanks for the input..
I plan on keeping the same pistons but put new rings and rebore the cylinders to make a good seal..as for camshafts..plan is to keep them as well however if I could get a set fairly cheap and in better nick than mine, then why not...
I think cleaning will be the most crucial bit in all the build...so no steps will be skipped. The squirters and the mains all get the oil feed from the balance shaft gallery as it acts as a junction to direct the oil where it's needed...basically it goes like: oil pump, oil filter, oil cooler, down to balance shaft and everywhere else...

 

[LostKiwi]

Thanks for the input..
I plan on keeping the same pistons but put new rings and rebore the cylinders to make a good seal..as for camshafts..plan is to keep them as well however if I could get a set fairly cheap and in better nick than mine, then why not...
I think cleaning will be the most crucial bit in all the build...so no steps will be skipped. The squirters and the mains all get the oil feed from the balance shaft gallery as it acts as a junction to direct the oil where it's needed...basically it goes like: oil pump, oil filter, oil cooler, down to balance shaft and everywhere else...

You can't rebore the cylinders and keep the same pistons as reboring will make the clearance to teh piston skirt increase and it will hence need oversize pistons.
You may be able to hone the cylinders depending what the cylinder material is (if its AluSil or NikaSil its not straightforward). If its AluSil I wouldn't be inclined to bother.

 

[Ge2tis]

You can't rebore the cylinders and keep the same pistons as reboring will make the clearance to teh piston skirt increase and it will hence need oversize pistons.
You may be able to hone the cylinders depending what the cylinder material is (if its AluSil or NikaSil its not straightforward). If its AluSil I wouldn't be inclined to bother.

Live and learn...thanks LostKiwi...I thought putting oversized rings would have solved it...but probably not..

 

[LostKiwi]

Live and learn...thanks LostKiwi...I thought putting oversized rings would have solved it...but probably not..

No. Definitely not.
Its important when fitting new pistons to measure the clearance between the skirt thrust faces and the bore. In general it needs to be 1 thousandths of an inch per inch of bore for cast pistons and up to double that for forged pistons. So if your engine has a 2.6" bore the piston clearance needs to be a minimum of 0.0026" but less than 0.005". As pistons (and rings) come in increments of 0.010" (typically) then if you bore the cylinder and refit the original piston it will wobble as it goes up and down the bore and on the combustion stroke the thrust face will 'slap' against the bore (this is what piston slap is). Excessive slap can lead to piston failure and breakage of the skirt which can in turn lead to rod failure as the piston gets forced out the side of the block.
Oversize rings are made for the oversize pistons. Simply fitting oversize rings to an existing piston in a bore which is too big for it will cause the rings to move a lot in the groove in the piston as the piston wobbles. This will lead to premature ring groove wear and piston failure (irrespective the piston slap issues already mentioned) and very poor gas sealing (hence low compression).

All the clearances in an engine must be observed and checked in order to prevent premature failures or excessive noise. If you have never built an engine I would strongly recommend you get an engine builder to do it or at least get someone who has done it before and knows what they are doing to show you how.

 

[Ge2tis]

No. Definitely not.
Its important when fitting new pistons to measure the clearance between the skirt thrust faces and the bore. In general it needs to be 1 thousandths of an inch per inch of bore for cast pistons and up to double that for forged pistons. So if your engine has a 2.6" bore the piston clearance needs to be a minimum of 0.0026" but less than 0.005". As pistons (and rings) come in increments of 0.010" (typically) then if you bore the cylinder and refit the original piston it will wobble as it goes up and down the bore and on the combustion stroke the thrust face will 'slap' against the bore (this is what piston slap is). Excessive slap can lead to piston failure and breakage of the skirt which can in turn lead to rod failure as the piston gets forced out the side of the block.
Oversize rings are made for the oversize pistons. Simply fitting oversize rings to an existing piston in a bore which is too big for it will cause the rings to move a lot in the groove in the piston as the piston wobbles. This will lead to premature ring groove wear and piston failure (irrespective the piston slap issues already mentioned) and very poor gas sealing (hence low compression).

All the clearances in an engine must be observed and checked in order to prevent premature failures or excessive noise. If you have never built an engine I would strongly recommend you get an engine builder to do it or at least get someone who has done it before and knows what they are doing to show you how.

Thanks again...this is a perfect example why these forums are so great...) I will try to find someone with the knowledge who could guide through the build but I want to do it myself...selfish, I know, and risky, but I want to start somewhere...to benefit in the long run.. so basically anyone with any kind of input is more than welcome and highly appreciated..