I have an oil leak from the sump on my Mk3 2.5 V6.  I have been told by the garage that this isn't simply a matter of replacing the sump gasket.  They have told me that they have done a compression test, and I have a broken ring on number five piston (obviously lower compression) and that this is pressurising the sump and causing a leak.  I know a fair bit about car mechanics, but I have NEVER heard this before and I feel I am about to be lined up to be ripped off!  Before I take the car back to the garage do you guys have any advice??

Many thanks!

I'd take it somewhere else and ask them to check it, second opinion kind of thing. I've never heard of this before. 

39 minutes ago, cpjvej2014 said:

I'd take it somewhere else and ask them to check it, second opinion kind of thing. I've never heard of this before. 

Thanks mate.   I feel that blocked breathers (not uncommon) is the issue here. A broken piston ring is extremely unlikely as this would result in (i) MoT failure on emissions - the car has just passed its MoT last week with perfect emissions (ii) Rough running - the car runs sweet as a nut (iii) Loss of power - there's no loss of power (iv) Burning oil - the car does not burn oil.

Basically someone is trying to rip me off; they said they had completed a compression test on the car, then when I asked them to service my other Mondeo, which is again a 2.5 V6 (exactly the same engine) they asked me to find out how to remove the spark plugs "...as it looks complicated"!! Mm....then how did you do the compression test on my other V6 Mondy??

There are also other jobs they have said they have done which they clearly haven't. What makes this worse?....this person has been a "friend" for almost twenty years.

17 minutes ago, The Archaeologist said:

  I feel that blocked breathers (not uncommon) is the issue here. A broken piston ring is extremely unlikely as this would result in (i) MoT failure on emissions - the car has just passed its MoT last week with perfect emissions (ii) Rough running - the car runs sweet as a nut (iii) Loss of power - there's no loss of power (iv) Burning oil - the car does not burn oil.
 

I  tend to feel that you are spot on. I can't see how you could break a piston ring without having some impact on oil consumption although that might be disguised if you have another cause of oil consumption.

Also if this does happen you blow air/oil mist through the crankcase but if the breathers are working it doesn't really pressurise anything.

Check that the sump plug isn't the source of the leak; I have seen this and it is not nice.

Quote

...and I have a broken ring on number five piston (obviously lower compression)...

And how would they now the difference between this and say low compression caused by a chipped valve?
 

Im needing to replace the sump gasket on my mk3...thats it...you would know if it was a broken ring...dont think it would sound too good...ive not heard of this line before...i know
ST mk3 petrols are driven hard, and sump gaskets are replaced and no more misting..they have two cats..if they are okay and breathers too then...
I have the one cat on my 3.0 v6..that is fine..also had ALL vacums and hard to get at breather replaced 1500 miles back..little bit of mist been like that since before..and after..is miniscule so not too worried, but will get done at fords when time allows...
Try another garage fella....

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