2nd hand engine supplier

[anonymous-user]

OK I have just removed the other 4 pistons - they all appear to be in good condition - all 3 rings on each one are intact and move freely, the pistons themselves dont have any marks on them anywhere, the tops have some black carbon crustiness and flakes on but no actual physical damage, and all the big end bearings, shells and crank journals are unmarked. The bores #1 to #4 are all slightly golden in colour and still have diagonal cross-hatching clearly visible , bore #5 is shiny silver with no cross-hatching but plenty of vertical wear marks, including the large scrape mentioned before at the rear of the bore.

I've also removed and checked the sump oil pickup, and as far as I can see into it with a torch the filter mesh looks clear and clean and not blocked.

Edited by anonymous-user on Monday 25th July 22:07

[anonymous-user]

Thinking it through - the black crusty carbon flakes on top of the pistons would suggest to me that oil is being burned, which ties in with it using about 1L of oil per 1000miles or so. There was a small amount of oil in the turbo outlet to the inlet manifold, so that would likely be the source of the oil. So I'm thinking that no matter what engine goes back in, it would be sensible to send the turbo to a specialist to have it checked and/or seals replaced / swapped for another one, to hopefully eliminate that oil burning issue. If I rebuild this engine the head will be going to an engineering company to be pressure tested / valves checked etc.. so that should remove any possible valve stem leaks etc...

I am also wondering whether a lump of the carbon crud could have become lodged in the rings on #5 and caused the large scrape marks leading to low compression, bad ignition and thus fuel wash and excessive bore wear.

All just guesswork on my part - does this theory make sense?

[stevieturbo]

JimSuperSix said:

Thinking it through - the black crusty carbon flakes on top of the pistons would suggest to me that oil is being burned, which ties in with it using about 1L of oil per 1000miles or so. There was a small amount of oil in the turbo outlet to the inlet manifold, so that would likely be the source of the oil. So I'm thinking that no matter what engine goes back in, it would be sensible to send the turbo to a specialist to have it checked and/or seals replaced / swapped for another one, to hopefully eliminate that oil burning issue. If I rebuild this engine the head will be going to an engineering company to be pressure tested / valves checked etc.. so that should remove any possible valve stem leaks etc...

I am also wondering whether a lump of the carbon crud could have become lodged in the rings on #5 and caused the large scrape marks leading to low compression, bad ignition and thus fuel wash and excessive bore wear.

All just guesswork on my part - does this theory make sense?

None at all. The large scrape marks are there because the piston has melted/blown into st through lack of fuel or poor/improper tuning or via detonation, or a combo of both.

Oil use could be various things...but most OEM engines with their PCV systems will tend to draw oil in and make a mess of everything. So it could be considered fairly normal and it keeps the hippies happy.
So the oil may or may not be coming from the turbo, and oil leaking past the compressor side of the turbo is rare, more often it's from the turbine side if there is a problem.
But unless breathers etc are blocked then usually the PCV, even if things get oily dont end up using lots of oil. That points more to bore issues. Whether that's engine age/mileage related..or it was never right from day one, who knows.

And piston crowns on any used engine are always dirty, it's normal. It would be more odd if they were very clean.

And ensure there are no hairline cracks or other damage on any of the other pistons. Dirt/carbon can easily hide these.

[anonymous-user]

OK that shoots down my theory

The local garage checked the PCV system and it was working OK.

So assuming I scrap this engine and get a replacement with coils , injectors and fuel rail , is there anything else I can check myself to do with the fueling? And what would cause detonation that is likely to still be in place if I installed that complete new engine?

[stevieturbo]

JimSuperSix said:

OK that shoots down my theory

The local garage checked the PCV system and it was working OK.

So assuming I scrap this engine and get a replacement with coils , injectors and fuel rail , is there anything else I can check myself to do with the fueling? And what would cause detonation that is likely to still be in place if I installed that complete new engine?

And as said before that depends what the actual cause was.

There could be issues with many parts of the fuel system from the ecu control, wiring, fuel pump/filter, injectors, boost control etc etc etc.
It could be related to the fuel itself, but I've never heard of "bad fuel" in the UK so chances of that are slim. Well I've heard claims...never seen it myself. People can make lots of things up to try and explain what they want to believe. Although stranger things have happened so fuel is a remote possibility too.

What will need done is everything rebuilt and someone competent to check everything is installed, running and behaving correctly after the rebuild.

It doesnt need to be a rolling road, but it does need to be with someone competent and able to check fueling, tuning, boost etc etc

Or if you believe it was an injector problem, you could send your existing set off to be tested, noting on them of course which cyl is which prior to sending off.
Not an overly expensive service.

[anonymous-user]

There is a rolling road / tuning place just down the road, I'll probably book the car in there (assuming I can get it working) to see if they can find anything amiss with the ECU / mapping etc...

I've ordered a replacement engine complete with injectors , coils and turbo, so I'll have plenty of spare parts at least.

[anonymous-user]

Looks like I've found the cause of the problem, or rather my engineer next door neighbour did when examining the cylinder head - under all the carbon crud there's an impact mark on the head that lines up perfectly with the misshapen area on piston 5, which looks quite a bit like the end of the outer electrode from a spark plug, and so what I thought was a melted part on the piston was actually where it had hit something in the cylinder and slightly compressed the piston edge and broken the top ring, which then led to blow-by and the scoring etc.. Just bad luck really that the contact occured right on the weaker edge of the piston above the ring groove, a couple of mm further in and it probably would have just left a small dent.

So that's good news, seems to have been a physical breakage rather than a fueling or spark issue etc..

New engine is in and running nicely (so far) , but I broke the auto-box shifter cable end so I have to fix that before I can drive it on the road.

[stevieturbo]

Sparks plugs rarely break ( although they can be broken )

And a missing plug tip is also a sure sign of detonation.

Although find it odd you never mentioned anywhere that a plug tip was missing when you took things apart ? Or is this a newly acquired vehicle with unknown history ?

[anonymous-user]

Yes we've had it for just a few months , spark plugs were all intact when I dismantled the engine so must have been damage that occurred before we bought it

I don't know for sure that its a spark plug tip, but the impact mark on the head is about the right shape - rectangular , neat sharp edges , a few mm long and perhaps 1mm wide. I'll take a photo of it if i get time.