Piston/Bore Wear

As part of my complete restoration/modification for overlanding, I stripped the engine completely today and cleaned up the pistons for inspection.

All was well until I looked at piston #4. You can see that it has been rubbing against the bore, which is consistent with some marks inside there too.

FYI, the big ends shells are worn too, with copper showing through the bearing surface. These will of course be replaced.

The engine was, according to the seller, running fine before removal; I have little reason to doubt him as I have dealt with him a couple of times and have had no issues. That said, the pedigree is unknown.

I'd like to seek some feedback on what may have caused this issue, and what steps are recommended to address this. Would re-honing sort this, or am I looking at a re-bore and oversized pistons? If the latter, I'm guessing that all four pistons/bores would need doing.

Photos to follow in a mo.

any pics ,any cylinder measurements , bearings down to the copper is common on many tdis due to age and mileage also lack of oil changes, id expect any tdi i stripped to find bearings showing copper

I'm trying to upload photos at the moment, but the site isn't letting me; it's saying that the files are too large when they're only 3mb!

Where there's a will, there's a way! The grooves look much deeper in the photos than in the flesh:

id say its been hot ,block might need flushing with core plugs removed using a pressure washer and a rebore with new pistons

Thanks - you were the man I had in mind when I saw the piston! The core plugs are already out and it looks like the rear one has been replaced before.

Would oversized pistons be required following a rebore, or just slightly larger rings? Or does it depend on measurements?

yes youd need over size pistons which come with rings , the cylinders are bored to the piston size minus clearance and minus 2 thou-ish to hone to final size,if its a standard cylinder now then plus 20 if any marks dont feel deep, once bored you need to gap the rings of each piston to the cylinder its going to be fitted to

Thanks James - I've touched base with a local (and reputable) engineering firm to get the ball rolling; I'll likely get them to de-coke the head, remove and refit the valves, as well as re-bore, re-hone, and fitting of new pistons/rings. I may drop the conrods over too as a couple of the bushes are showing some copper.

@jamesmartin - is re-lining #4 and replacing #4 piston a sensible option? Seems that this should be considerably cheaper than full re-bore, hone, 4x new pistons etc...

its possible, rebore and 4 new pistons is preferred choice ,what difference in price have you been given as reboring 4 isnt likely much dearer than linering one

Thanks. I haven't got prices yet, but thought it worthwhile to check with an expert to see if it's an option or not.

The block has been inspected; he reckons we may be able to remove the (exceptionally shallow) scores by honing alone. If not, then all four will need boring and honing etc.

The block needs boring and honing...ah well.

Best get myself a set of +20 pistons...

Best idea, donit right first time and you will have a better engine at the end of it

I should have a load of parts from Turner Engineering arriving today

Sting Ray said:

I should have a load of parts from Turner Engineering arriving today

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That's where I bought my gear from for my engine refurb. Very helpful people. Did you get the KolbenSchmidt pistons? Actually, they may not sell another make?

Al2O3 said:

That's where I bought my gear from for my engine refurb. Very helpful people. Did you get the KolbenSchmidt pistons? Actually, they may not sell another make?

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Yes, I got those pistons; I think they sell aftermarket ones as well, but like you, I'm keen to stick to LR parts where the quality is vital. When I accidentally ordered too much, they phoned me up to let me know of my mistake, amended the order, and refunded the money straight away - excellent service.

Your thread taught me a lot by the way, so thanks for that. Unfortunately I neglected to note which thrust washers go where. I've ordered a DTI (never used one), so will hopefully be able to measure crank end float and add the right washers to the correct part of the crank. Did you fit new ones?

Sting Ray said:

Yes, I got those pistons; I think they sell aftermarket ones as well, but like you, I'm keen to stick to LR parts where the quality is vital. When I accidentally ordered too much, they phoned me up to let me know of my mistake, amended the order, and refunded the money straight away - excellent service.

Your thread taught me a lot by the way, so thanks for that. Unfortunately I neglected to note which thrust washers go where. I've ordered a DTI (never used one), so will hopefully be able to measure crank end float and add the right washers to the correct part of the crank. Did you fit new ones?

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Morning Sting Ray.
Yeah, Frida Turner is very efficient and helpful.
Are there not slots for the thrust washers to go in, so it's easy to know where they live? I'll have to go back and look at the pictures. I used RTC2825, which I think is standard size, no idea why I decided that now! Did you buy a dial test indicator or a dial indicator? @neilly will be watching to make sure you are using the correct terminology

Sting Ray said:

Yes, I got those pistons; I think they sell aftermarket ones as well, but like you, I'm keen to stick to LR parts where the quality is vital. When I accidentally ordered too much, they phoned me up to let me know of my mistake, amended the order, and refunded the money straight away - excellent service.

Your thread taught me a lot by the way, so thanks for that. Unfortunately I neglected to note which thrust washers go where. I've ordered a DTI (never used one), so will hopefully be able to measure crank end float and add the right washers to the correct part of the crank. Did you fit new ones?

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thrust washers fit on no3 main bearing in slots in the block copper or white metal side faces the crank

jamesmartin said:

thrust washers fit on no3 main bearing in slots in the block copper or white metal side faces the crank

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That's what I was trying to say