BMW M5 piston ring failure one cylinder possible costs
Discussion
Was diagnosed by BMW main dealer cylinder 7 piston ring failure and no compression in cylinder 7, others seems fine. I know it's major task but in this case it's only 28000 miles so it's not that all engine worn out. Car was ECU tuned to 680bhp. I'm just thinking what parts most likely need to replace only piston ring or something else. Car is not much driven after this maybe 10 miles. I know if it was wear and tear it would be huge job and many parts need replacing. But this car is low mileage and I think other pistons and cylinders are fine. Of course tomorrow I go to mechanic independent specialist but today got offer to sell but for very low price just thinking if this could be few thousand job like 2-3 thousands or any case 10000+ job...?
I would struggle to believe a dealer would be capable of such a diagnosis. But it is possible.
And given the fact it is not standard....it's not quite "piston ring failure", more likely piston rings damaged through detonation by poor tuning and/or fuel, or some other similar causation. Not simply component failure.
And it is unlikely that if they have came to a conclusion of piston ring damage, then very likely there is also piston damage, possible bore damage, and perhaps more.
Some of which is easy to get a good idea of with a borescope, so would presume they have already done this and advised ? But some piston damage may not be visible from above, and does require them removed and thoroughly inspected.
And "no compression" would rarely be a piston or ring issue. Usually "no compression" is a valve related problem. So either they've tested poorly, the wording of the description of the test result is poor....or a piston is completely and utterly f
ked. But then that would lead to a little more of a diagnosis than "piston ring failure"
Until the engine is apart you wont know. It's gona be expensive though.
And given the fact it is not standard....it's not quite "piston ring failure", more likely piston rings damaged through detonation by poor tuning and/or fuel, or some other similar causation. Not simply component failure.
And it is unlikely that if they have came to a conclusion of piston ring damage, then very likely there is also piston damage, possible bore damage, and perhaps more.
Some of which is easy to get a good idea of with a borescope, so would presume they have already done this and advised ? But some piston damage may not be visible from above, and does require them removed and thoroughly inspected.
And "no compression" would rarely be a piston or ring issue. Usually "no compression" is a valve related problem. So either they've tested poorly, the wording of the description of the test result is poor....or a piston is completely and utterly f
ked. But then that would lead to a little more of a diagnosis than "piston ring failure"Until the engine is apart you wont know. It's gona be expensive though.
Edited by stevieturbo on Sunday 10th March 14:25
I see smoke coming from oil cap so yes seems really piston ring failed 
"6. Broken Piston Ring: If a particular cylinder piston ring breaks it will allow cylinder compression to leak outward into the crankcase. To check for this condition remove the oil fill cap when the engine is running and you will see a distinctive pulse of smoke forced outward from the inside of the engine. A compression test will be able to pinpoint which cylinder has malfunctioned and needs repair. "
I hope that no need to replace other components only one piston etc. Which shouldnt be super crazy expensive like close to 10K
(that is quote for full engine rebuild changing everything) if it's 2-3K fine. Because I bought car ~10K cheaper then market rate.
"6. Broken Piston Ring: If a particular cylinder piston ring breaks it will allow cylinder compression to leak outward into the crankcase. To check for this condition remove the oil fill cap when the engine is running and you will see a distinctive pulse of smoke forced outward from the inside of the engine. A compression test will be able to pinpoint which cylinder has malfunctioned and needs repair. "
I hope that no need to replace other components only one piston etc. Which shouldnt be super crazy expensive like close to 10K
(that is quote for full engine rebuild changing everything) if it's 2-3K fine. Because I bought car ~10K cheaper then market rate.
rikardo_82 said:
I see smoke coming from oil cap so yes seems really piston ring failed
"6. Broken Piston Ring: If a particular cylinder piston ring breaks it will allow cylinder compression to leak outward into the crankcase. To check for this condition remove the oil fill cap when the engine is running and you will see a distinctive pulse of smoke forced outward from the inside of the engine. A compression test will be able to pinpoint which cylinder has malfunctioned and needs repair. "
I hope that no need to replace other components only one piston etc. Which shouldnt be super crazy expensive like close to 10K
(that is quote for full engine rebuild changing everything) if it's 2-3K fine. Because I bought car ~10K cheaper then market rate.
it costs as much in time and labour to strip an engine to pull one piston as it does 8 or 10.."6. Broken Piston Ring: If a particular cylinder piston ring breaks it will allow cylinder compression to leak outward into the crankcase. To check for this condition remove the oil fill cap when the engine is running and you will see a distinctive pulse of smoke forced outward from the inside of the engine. A compression test will be able to pinpoint which cylinder has malfunctioned and needs repair. "
I hope that no need to replace other components only one piston etc. Which shouldnt be super crazy expensive like close to 10K
(that is quote for full engine rebuild changing everything) if it's 2-3K fine. Because I bought car ~10K cheaper then market rate.
For a car like that, needing such work.....2-3k is living in noddy land. If you're doing the labour itself, then 2-3k maybe realistic in parts alone. ( not including any machining work that may be needed )
hmm for what parts 2-3K? If problem in one cylinder??? then if all engine was broke parts would be 3X8=24K ????
Yes I agree labour is same to strip and open engine but it may need change components only for one cylinder not for all engine so still overall less job compared for full engine rebuilt if it was worn out after 200K miles. Plus need to buy parts only for one cylinder not all engine.
Yes I agree labour is same to strip and open engine but it may need change components only for one cylinder not for all engine so still overall less job compared for full engine rebuilt if it was worn out after 200K miles. Plus need to buy parts only for one cylinder not all engine.
rikardo_82 said:
Hm you think one piston could cause all engine failure? Because as I understand compression in other cylinders is fine also no knocking noise etc just rough engine sure I put tomorrow in garage and they will check maybe tuesday. Just stressed now about costs
So you've went from one piston/ring failure ( a guess....not a proper diagnosis )...to "all engine failure" ?Which is it ? And you have no notion what state the rest of the engine is in...and nor will they until it is all stripped. But you can be sure if one is damaged, then there is a high likelihood of other damage.
rikardo_82 said:
hmm for what parts 2-3K? If problem in one cylinder??? then if all engine was broke parts would be 3X8=24K ????
Yes I agree labour is same to strip and open engine but it may need change components only for one cylinder not for all engine so still overall less job compared for full engine rebuilt if it was worn out after 200K miles. Plus need to buy parts only for one cylinder not all engine.
Dont be an idiot.Yes I agree labour is same to strip and open engine but it may need change components only for one cylinder not for all engine so still overall less job compared for full engine rebuilt if it was worn out after 200K miles. Plus need to buy parts only for one cylinder not all engine.
If your engine has suffered ring damage then it'll very likely have scored the cylinder, so it'll either need honing or more likely boring / new sleeve (I cannot remember if the s63 has sleeves or not). If it needs boring then you're in for 8 new pistons and sleeves in my opinion you don't want one over sized piston. If there is any damage to the rod then you will need a new rod and you will need to fit new rod bearings.
If the block just needs honing then it'll be an engine out job to hone the block. Then you need a new set of rings, possible piston, new rod bearings and possible rod if damaged.
In either scenario the engine HAS to come out. You cannot just fit new rings and hope for the best. The block must be bored otherwise you're going to risk more damage / have a badly running engine.
If you think that you can do this for £3k then you are in lah lah land.
If the block just needs honing then it'll be an engine out job to hone the block. Then you need a new set of rings, possible piston, new rod bearings and possible rod if damaged.
In either scenario the engine HAS to come out. You cannot just fit new rings and hope for the best. The block must be bored otherwise you're going to risk more damage / have a badly running engine.
If you think that you can do this for £3k then you are in lah lah land.
The actual diagnosis for your engine based on what you have said so far is "loss of compression on one cylinder" and not piston ring failure. Yes the piston rings may well be broken but it's vanishingly unlikely thewy just did that one their own. More likely is the piston ring lands broke due to detonation which broke the rings and caused them to stop sealing. Broken rings flying up and down in a broken piston do not bode well for the cylinder bore. If there has indeed been detonation then this will very likely have damaged the cylinder head too.
In short you have no idea what sort of repair may be needed, or even if one is still possible, or what it might cost. A main dealer is the worst possible place to go to for such work anyway. You'd be better off with a race engine specialist.
In short you have no idea what sort of repair may be needed, or even if one is still possible, or what it might cost. A main dealer is the worst possible place to go to for such work anyway. You'd be better off with a race engine specialist.
yes I wouldn't go also to main dealer I bought car and seller did diagnostic. I will tomorrow call BMW specialists who knows M cars
BMW dealer charged 400 pounds for this "diagnostic" so I guess they worked around 2H max on car. As far as I read myself all day it is possible to pinpoint problem pressurizing cylinder and and watching where air escapes.
BMW dealer charged 400 pounds for this "diagnostic" so I guess they worked around 2H max on car. As far as I read myself all day it is possible to pinpoint problem pressurizing cylinder and and watching where air escapes.
Agree a main dealer is the last pla e to take it, when was the last time a main dealer stripped an engine?
Also I don't know how they can confidentially say its a piston ring failure from lack of compression. If it has no compression it's more likely to be a valve not seating for some reason but it's a basic test that tells you little more than you have an issue.
Its highly unlikely you will have lost significant compression for just a ring, if it's failed that badly it would have done the bore which is strip the engine down to the block and re-plate or sleeve then hone like others have said.
Probably cheaper to get a second hand engine and be happy with 550bhp.......
Either way I'd imagine its the far side of £10k, lucky to repair that for less.
Also I don't know how they can confidentially say its a piston ring failure from lack of compression. If it has no compression it's more likely to be a valve not seating for some reason but it's a basic test that tells you little more than you have an issue.
Its highly unlikely you will have lost significant compression for just a ring, if it's failed that badly it would have done the bore which is strip the engine down to the block and re-plate or sleeve then hone like others have said.
Probably cheaper to get a second hand engine and be happy with 550bhp.......
Either way I'd imagine its the far side of £10k, lucky to repair that for less.
rikardo_82 said:
yes I wouldn't go also to main dealer I bought car and seller did diagnostic. I will tomorrow call BMW specialists who knows M cars
BMW dealer charged 400 pounds for this "diagnostic" so I guess they worked around 2H max on car. As far as I read myself all day it is possible to pinpoint problem pressurizing cylinder and and watching where air escapes.
You have already been given a diagnosis that tells you the engine needs to come apart.BMW dealer charged 400 pounds for this "diagnostic" so I guess they worked around 2H max on car. As far as I read myself all day it is possible to pinpoint problem pressurizing cylinder and and watching where air escapes.
And how do you think you are going to "watch" where air escapes...inside the engine.
When you dont need to anyway, because your compression test with "no compression" as you put it....has told you all you need to know at this time. Which is the engine needs to come apart.
As incompetent as most main dealers are, that text is pretty specific and I would hope even they couldnt get that basic test wrong.
There really isnt anything else you need to read online or other, so as to try and mislead yourself a different direction or some route that might end up costing even more.
Of course you also seem to be implying, you knowingly bought this car cheap, and it was the seller who gave you this report ? And with such damage you cannot properly test drive this vehicle.....
You may hope the engine is the only problem here.
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