IanH's 955hp V10 Audi RS6 - Another Car Diary!
Discussion
So got the spring out yesterday
and got my 16mm spark plug socket today and whipped the plug out.It looks OK with no damage, it's just coated in oil stopping it firing -
And the boroscope, despite being producing an absolutely awful pic, doesn't show any obvious signs of damage, just more oil burning, so the oil doesn't look to be coming past the rings so it must be coming coming down through the heads which makes me think Valve Stem Oil Seal but the boroscope pics aren't clear enough to be absolutely sure -
and got my 16mm spark plug socket today and whipped the plug out.It looks OK with no damage, it's just coated in oil stopping it firing -
And the boroscope, despite being producing an absolutely awful pic, doesn't show any obvious signs of damage, just more oil burning, so the oil doesn't look to be coming past the rings so it must be coming coming down through the heads which makes me think Valve Stem Oil Seal but the boroscope pics aren't clear enough to be absolutely sure -
Well a massive fingers crossed there, i would be surprised at Valve stem seals given the age of the engine, regardless of power output above standard.
Definitely worth compression testing that cylinder if you can whilst the plug is out and you have access. Have you looked at any plugs from any other cylinders to see if it is completely isolated to number 1?
Definitely worth compression testing that cylinder if you can whilst the plug is out and you have access. Have you looked at any plugs from any other cylinders to see if it is completely isolated to number 1?
but with the engine doing 108K miles, with 20k+ of that being over 700hp, I'd expect the bores to all look similar but the plugs to all look normal.IanH755 said:
There a V-Max type event I'm looking at sometime in Spring, just need to get this issue sorted first.
Sounds good, yeh sounds like a pretty complex issue with the burnt oil spewing out. My first port of call would be the RS246 forum but I guess you've already been there?That's a heck of a lot of oil on the plug, would be a huge amount to be getting past a valve stem oil seal, down the valve guide and into the cylinder. One would have expected more gradual oil consumption if wear related, which you probably would have noticed as it would have blue smoked from the exhaust more and more.
To suddenly lose one cylinder suggests some sort of catastrophic failure.
As already suggested above, a check of the crankcase breather is a good first step. Was there any oil in the inlet manifold at all? That boroscope picture is hard to tell, but is that a slight scoop out of the edge of the crown at the bottom of pictures 1 and 3? Seems a compression check is a logical next step.
To suddenly lose one cylinder suggests some sort of catastrophic failure.
As already suggested above, a check of the crankcase breather is a good first step. Was there any oil in the inlet manifold at all? That boroscope picture is hard to tell, but is that a slight scoop out of the edge of the crown at the bottom of pictures 1 and 3? Seems a compression check is a logical next step.
larrylamb11 said:
That's a heck of a lot of oil on the plug, would be a huge amount to be getting past a valve stem oil seal, down the valve guide and into the cylinder. One would have expected more gradual oil consumption if wear related, which you probably would have noticed as it would have blue smoked from the exhaust more and more.
To suddenly lose one cylinder suggests some sort of catastrophic failure.
As already suggested above, a check of the crankcase breather is a good first step. Was there any oil in the inlet manifold at all? That boroscope picture is hard to tell, but is that a slight scoop out of the edge of the crown at the bottom of pictures 1 and 3? Seems a compression check is a logical next step.
Intake - No oil in the intake pipes, 1-2 drops in the turbo intake, Oil separator could do with being taken off and checking as there is a little oil in the pipes from it but need a thinner torq bit holder (mine are 3/8, needs 1/4) to do it due to a lack of space.To suddenly lose one cylinder suggests some sort of catastrophic failure.
As already suggested above, a check of the crankcase breather is a good first step. Was there any oil in the inlet manifold at all? That boroscope picture is hard to tell, but is that a slight scoop out of the edge of the crown at the bottom of pictures 1 and 3? Seems a compression check is a logical next step.
Bore Pics - These are taken at 90' steps around the cylinder so the "missing bit" in pic 1 and 3 is actually two bits "missing" from two different places 180' apart.
The reason for losing a cylinder was the oil on the plug. I just need to find out how the oil is getting there. It looks pretty burnt on so I'm wondering how long the oil has been there as the car has always used oil (1L per 1500 miles). Next step would be taking another few plugs out to check their condition and bore inspection followed by a compression test (if I had one handy which I don't) so instead I'm going to clean up the plug, refit it and start the engine then recheck the plug for fresh oil.
Would agree. I know 2-stroke cylinder damage far better, but if that was a chainsaw, I'd be expecting the rings to have transferred to the cylinder wall and a whole load of melting on the side of the piston when it comes out.
Can you compression test that cylinder? Or stick the camera in a different cylinder to compare bore marks?
Will be a bit gutting if that is the case, hope it's not. But I can't see how a valve stem seal would suddenly go.
Can you compression test that cylinder? Or stick the camera in a different cylinder to compare bore marks?
Will be a bit gutting if that is the case, hope it's not. But I can't see how a valve stem seal would suddenly go.
I have seen some tools that enable you to change the stem seal without removing the head - they use compressed air in the combustion chamber to hold the valve shut. But you still have to remove the cam shaft and IIRC the spring has to be relatively weak. Can't see it being practical on an RS^ so if it is that, then you're into a top end rebuild anyway. You could always drop the sump and pull the pistons out whilst you're at it.
Also, IME, the stem seals don't fail catastrophically. they either wear or harden over time leading to a gradual increase in oil being sucked in on over-run and burnt off.
Also, IME, the stem seals don't fail catastrophically. they either wear or harden over time leading to a gradual increase in oil being sucked in on over-run and burnt off.
Edited by Zombie on Friday 30th December 19:30
I'm afraid I think I agree that the piston looks slightly deformed in one place and there definitely seems to be a mark up the bore. I hope not for your sake. Compression/cylinder leakage test required I think. If your crankcase breathing is ok I can't see it just being a valve stem seal.
I hope I'm wrong!
I hope I'm wrong!
Mikeeb said:
I'm afraid I think I agree that the piston looks slightly deformed in one place and there definitely seems to be a mark up the bore. I hope not for your sake. Compression/cylinder leakage test required I think. If your crankcase breathing is ok I can't see it just being a valve stem seal.
I hope I'm wrong!
Would you mind explaining what that means to this engine. I assume it's just a new piston and bits not a completely destroyed engine? What is the worst case here.I hope I'm wrong!
Burwood said:
Would you mind explaining what that means to this engine. I assume it's just a new piston and bits not a completely destroyed engine? What is the worst case here.
It means a destroyed engine block on the V10 RS6 as you can't hone or bore out the cylinder due to the liner fitted, so any cylinder damage means a new block if it's lost compression. I've got a spare block lined up just incase 
IanH755 said:
Burwood said:
Would you mind explaining what that means to this engine. I assume it's just a new piston and bits not a completely destroyed engine? What is the worst case here.
It means a destroyed engine block on the V10 RS6 as you can't hone or bore out the cylinder due to the liner fitted, so any cylinder damage means a new block if it's lost compression. I've got a spare block lined up just incase This would probably be more expensive than using a stock block though. And pointless if the stock unit can take the beating.
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