Daf
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| posted on 28/3/16 at 08:23 PM |
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Marks on cylinder bore
Evening all, my engine was low on compression on cylinder no 2 - circa 80psi compared to 150 on the other 3. After taking the head off there's
no obvious signs of damage to the head or gasket but I have noticed these marks on the cylinder wall of the offending cylinder:
Has anyone seen marks like this before? The history of the engine is unknown to me - and the car isn't on the road yet so it's not a
failure that's occured during my ownership. Any thoughts on this would be much appreciated.
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madteg
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| posted on 28/3/16 at 08:30 PM |
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Only a guess but i would say. Engine has been left for a number of years and piston ring have corroded, that is why you can see ring marks. Possibley
water in the cylinder or plugs left out.
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Daf
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| posted on 28/3/16 at 08:41 PM |
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quote:
Originally posted by madteg
Only a guess but i would say. Engine has been left for a number of years and piston ring have corroded, that is why you can see ring marks. Possibley
water in the cylinder or plugs left out.
So quite likely the casue of low compression then if I have a corroded piston rings?
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mark chandler
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| posted on 28/3/16 at 08:47 PM |
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If you cannot feel any ridges then rough the bore with some wet and dry following the honing marks on all cylinders then fit a new set of rings.
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perksy
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| posted on 28/3/16 at 09:16 PM |
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As above Its been standing or possibly started up and then turned off without getting up to full working temperature
Try and see if you can catch the marks with your nail or not, Hopefully it will be the latter...
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Daf
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| posted on 29/3/16 at 07:10 AM |
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quote:
Originally posted by perksy
As above Its been standing or possibly started up and then turned off without getting up to full working temperature
Try and see if you can catch the marks with your nail or not, Hopefully it will be the latter...
Nope can't feel them which is good news, is it worth me re-honing the bore?
Any recommendations an piston rings for the zetec blacktop engine?
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britishtrident
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| posted on 29/3/16 at 12:13 PM |
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It is probably a stuck ring the pitting is due to moisture ingress via the inlet or exhaust.
But a drop to 80psi from 150 is huge for a piston ring problem alone. I would also check the valves
It would have been nice to do both dry & wet cylinde leak-down tests before stipping as this can usually give better clues as to what to look
for.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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Daf
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| posted on 29/3/16 at 12:19 PM |
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quote:
Originally posted by britishtrident
It is probably a stuck ring the pitting is due to moisture ingress via the inlet or exhaust.
But a drop to 80psi from 150 is huge for a piston ring problem alone. I would also check the valves
It would have been nice to do both dry & wet cylinde leak-down tests before stipping as this can usually give better clues as to what to look
for.
To be honest when I saw 80PSI I was expecting to find an obvious issue when I took the head off - however other than those marks on the bore
there's nothing sinister looking at all.
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britishtrident
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| posted on 29/3/16 at 12:20 PM |
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quote:
Originally posted by Daf
quote:
Originally posted by perksy
As above Its been standing or possibly started up and then turned off without getting up to full working temperature
Try and see if you can catch the marks with your nail or not, Hopefully it will be the latter...
Nope can't feel them which is good news, is it worth me re-honing the bore?
Any recommendations an piston rings for the zetec blacktop engine?
Just roughening the bore surface with a fairly coarse abrasive should be enough ( ie "glaze bust" as the orignal cross hatch hone pattern
is still clearly visible.
The surface texture just needs to be rough enough to retain an oil film as the rings pas over it.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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britishtrident
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| posted on 29/3/16 at 12:26 PM |
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quote:
Originally posted by Daf
quote:
Originally posted by britishtrident
It is probably a stuck ring the pitting is due to moisture ingress via the inlet or exhaust.
But a drop to 80psi from 150 is huge for a piston ring problem alone. I would also check the valves
It would have been nice to do both dry & wet cylinde leak-down tests before stipping as this can usually give better clues as to what to look
for.
To be honest when I saw 80PSI I was expecting to find an obvious issue when I took the head off - however other than those marks on the bore
there's nothing sinister looking at all.
You can test the valve sealing easy enough there are a couple of ways of doing it using kerosene. The way I use is with the head lying on its edge to
fill the port with kerosene and direct a jet of compressed air round into the combustion chamber round the periphery of the valve and look for tiny
bubbles in the port. The more conventional way is just fill the combustion chamber with kerosene and loo for leaks.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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