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Tdi Bore Wear


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Hi folks.

My Tdi runs well, but has suffered excessive oil consumption ever since I hooked it out of a Discovery.  The head had recently been rebuilt, but I was suspicious, so removed it and found seizure damage in the no.1 bore.  So the block was bored +20thou and new pistons and rings fitted.  

It has always started and run perfectly except using about a pint of oil every 500 miles or so, and seems to produce a little blue smoke at idle or on overrun, but not when working.  Two rebuilds of the turbo (due to the first being by a ripoff company, but the later being perfect by Turbo Technics) and another head skim, pressure check and valve and guide check after the composite head gasket leaked has not changed the oil consumption, so it seems to be in the block.

Now, here's the kicker.  The rebore left the damaged part of no.1 with no scoring at all, but it looks a little polished on that spot with very weak honing compared to the rest.  I'm not sure it isn't a tiny bit oval.  I had sent photos to several other renowned LR engine specialists and they reckoned it should be OK, but given the head and turbo reworking, it's my prime suspect.

Do you reckon that pulling the piston and using one of the rings with a torch on one side would work to reveal any ovality in the suspect area?  If it does, it is acceptable to have just the one cylinder rebored to +40, rather than all four, and if not, is a liner bored to +20 to reuse the current pistons and only face the cost of the work on one cylinder cheaper than reboring all and buying new pistons and rings?  If diesel hasn't been made prohibitive by the time I come home, I'll need to do this.

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Before ripping it open again, it could be your rings haven't yet bedded properly. There are many opinions on the best way to run in; mine is use a mineral or running in oil and don't be gentle, but do ease off the power occasionally, but doubtless there are others. You could try Millers Glaze Bust (Product code 5408) if you think the bores have glazed.

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It has done about 40k, so the engine is as bedded in as it'll get.  Glazing is possible, though, especially as I started using vegoil before 1000 miles was up.  I did use running in oil for 500 and then 1000 miles, and I did give it a bit of a run on the commute to try to prevent any glazing.  The vegoil bit wasn't protracted and it was only done with the engine hot and the fuel running through a heat exchanger (multi tank system), but you never know.  I also don't know how accurate the boring was.  But that smooth patch makes me suspicious.  I will try the deglazer.

As for the most cost effective repair, is the one +40 piston and the thee others at +20 enough of a mass difference to make it lumpy, or is it acceptable?  And is a single liner and bore out to +20 to retain the existing pistons going to be cheaper than boring all out to +40 and a full set of pistons?

 

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My 200tdi was rebuilt about 13000 miles since rebore and new pistons.... It gets 1 oil top up between oil changes at 6000 miles.. It takes about 3/4 of a litre to get back to the max mark.

Is your engine breathing when it runs? 

Bores and pistons should be the same size. New liners in a block and same piston about the same price as rebore and new pistons according to my local engine specialist.

If the bore has cleaned up to remove the damage then it's round... When the engine was put back together, we're the ring gaps staggered? And when the stem seals were replaced, where the seated fully home and not damaged. I rebuild a cylinder head for a friend and found a stem seal.had come adrift.

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If you want to check the bore using a piston ring, then you really need to use a new one to check for ovality. General bore wear can be determined by fitting the old ring placed squarely 1/3 of the way down the bore and measuring ring gap. With a new re-bore matched to the pistons should ensure all are the same. Things that could affect that are really small ends or other problems - diesel wash/injector problems, etc, but I would expect piston crown evidence to show that.

 

 

Les

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13 hours ago, vulcan bomber said:

My 200tdi was rebuilt about 13000 miles since rebore and new pistons.... It gets 1 oil top up between oil changes at 6000 miles.. It takes about 3/4 of a litre to get back to the max mark.

Is your engine breathing when it runs? 

Bores and pistons should be the same size. New liners in a block and same piston about the same price as rebore and new pistons according to my local engine specialist.

If the bore has cleaned up to remove the damage then it's round... When the engine was put back together, we're the ring gaps staggered? And when the stem seals were replaced, where the seated fully home and not damaged. I rebuild a cylinder head for a friend and found a stem seal.had come adrift.

It's using more than that - 1/5l for anywhere between 500-1000 miles depending on use, but consumption is worst when the engine is working lightly and least when working hard.  It is breathing a fair bit; I have the breather running into the Tee on the inlet to the 19J filter housing and I use a K&N to prevent the filter clogging or getting so wet that it collapses. A paper filter would need replacing every service (I use 5000 mile intervals).  It burns a little oil and this is most visible at low revs and on over-run, tying in with what I said about consumption when working easily or slogging.

I was careful to set each ring gap 120 degrees apart.  The valve stemn seals were an early suspect and were replaced once before the head rebuild and again during the head rebuild (it was pressure checked too).

I'll take a look through my archives for a photo of the polished spot (I sent it at the time to the reputed specialists, not the local shop who did the machining for me, for an opinion that they gave as not ideal, but satisfactory).  I recall it having extremely light, fine honing marks suggesting the honing stones had just kissed the surface on the way past, which made me suspect the shallowest of hollows.

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9 hours ago, Les Henson said:

If you want to check the bore using a piston ring, then you really need to use a new one to check for ovality. General bore wear can be determined by fitting the old ring placed squarely 1/3 of the way down the bore and measuring ring gap. With a new re-bore matched to the pistons should ensure all are the same. Things that could affect that are really small ends or other problems - diesel wash/injector problems, etc, but I would expect piston crown evidence to show that.

 

 

Les

The pump and injectors were reconditioned while the block was being done, and they have always seemed good.  I get instant starts, even when we had the -17 degrees spell, without using the glow plugs, so I think the fuel system is doing its thing.  The new bore dimensions, pistons and rings should all be matched; the engineering shop that did the boring provided the pistons - they insisted on having them to measure them for the boring.  I don't hear any slap or knocking, but Tdis aren't that quiet, so perhaps the boring was a little to big and the ring gaps are excessive?  I'm trying to run through every potential cause and rule them out - I think it's not the head or turbo, so it has to be in the bottom end, and that must mean bores, pistons or rings.  I'll see if I also have a picture of the ring gap.

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I think if you are going to all the effort of stripping & reboring, rather than doing  just one cylinder then I'd go for the full set of +40 and be done.with it  What if they were all to blame for whatever reason? You don't want to have to do it twice. I know it is more cost, but if it's done right you know it'll be OK for a long time. 

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  • 2 weeks later...

It has been consistent ever since I installed the engine, which was after the rebore.  It has always been run on the mineral 10W40 since finishing the running in.  The head rebuild and two replacement turbos (one was a bodge by a company in Reading) made no difference, hence my belief it's the block area causing the problem.

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It's your call Nick - but you said right back at the start that it runs well.

Using oil isn't going to kill it - if it gets worse then do something about it.  If it was me and I lived in sandy placmy s and was earning a big wad, I'd but a spare donk, ship it to my workshop and do a Boydie. Build a new one. Stage 2 head, balanced crank and pistons - the full banana. Then ship it home ready for retirment and fitting

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Ha!  I wish I could do that!  The shipping would cost as much as just getting a short engine from one of the top UK re-manufacturers, and rebuilding an engine in an open sided garage with all this dust isn't going to do it any favours, otherwise I'd be working on the RR out here!  Besides, I need to save all the money I can between now and coming home for rebuilding the RRC and perhaps that ZF before fitting it to the 109, but more importantly and costly than both of those together will be my kids' university costs.  Trust me, we're not living the high life, we're having to be reasonably frugal!  

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Nick

You fly planes - just get an extra box chucked on the baggage hold next time you're over here. As for the garage - the engine and stand will fit in your sitting room!

Let the kids learn about debt management early in life

As for the High Life - you know Streaky and Tim and they live the highest life; so sit in their shadows

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I'm no expert. But have you tried it on 15w40 oil? Mind I spose when it's warm it will make no difference. 

My 300tdi isn't the best engine,  it's noisy and down on power. However,  it doesn't use a drop of oil between services either. Just thought it's worth a mention 

 

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Mine both use oil, but I've never been able to get the oil filters to stop leaking.  I always use quality filters, I always clean the faces, I always oil the O ring.  I've tried really tight, I've tried barely tight, I've done the old quarter turn...always they leak.  Got a constant streak down the side and a drip hanging off the bottom, and being placed where they are that means right onto the front prop too.....luckily I have FWH, otherwise it'd be all over everything....

 

Sure it's not something as simple as that Nick?

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Mine does leak a bit from there too, enough to make it wet but not enough for the prop to fling it about.  Certainly not enough to reflect the level drop.  In normal use, I only needed to top up every fortnight.  That's not a big deal, but it is a slight nuisance and it'd be good to trust it more.  Given the cost of a rebore and new pistons and rings versus the oil consumption, I'll just leave it unless it gets markedly worse.  Disappointing, though.  I might have a go at honing, though, just in case the bores glazed during the running in period and have never cleared since - that could explain the vertical lines from the not very hard coke in the photos I put up (they were post rebore).

Quickly looking at the Turner site for piston prices, I saw the cooling jets.  I reused the original jets, but one or two were slightly bent and I realigned them.  Now, I don't imagine they're especially accurate as new, but if my realignments weren't quite good enough, would this be a likely candidate?  I'd imagine they'd need to be well off to cause a problem, squirting at the cylinder wall.  Maybe a bit of dirt inside one or more of them is aerosolising the oil spray and misting the walls?

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On 30/09/2016 at 7:06 PM, ejparrott said:

Mine both use oil, but I've never been able to get the oil filters to stop leaking.  I always use quality filters, I always clean the faces, I always oil the O ring.  I've tried really tight, I've tried barely tight, I've done the old quarter turn...always they leak.  Got a constant streak down the side and a drip hanging off the bottom, and being placed where they are that means right onto the front prop too.....luckily I have FWH, otherwise it'd be all over everything....

 

Sure it's not something as simple as that Nick?

Have you replaced the o-rings in the cooler pipes and the oil thermostat ?

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