Impreza turbo leak down diagnosis help please...

[dern]

Last week I started my my99 uk turbo wagon and blue smoke came out the exhaust. I read up on the possible causes and all of the turbo diagnosis web pages suggested that the air filter becoming blocked could pull oily vapour through the breather hoses so I swapped the k&n for a paper filter just to check that and got rid of all the blue smoke. I posted on this subject last week by the way and someone also suggested that a blocked air filter could do this.

Anyway today I decided to do a leak down test just to make sure the engine was good. I pulled all the spark plugs and they're all lovely and light brown except for number 2 cylinder which is oily. I did a compression test first and all the cylinders produced 150psi except number two which produced less than 50psi. I then did a leak down test and all the cylinders came up with 15% which I think it ok except for number 2 which produced 95% leak down which is obviously not. I get no bubbles out of the coolant and no air noises coming from the air intake or the exhaust. Sticking a rubber hose down the oil filler and the other end to my ear and I can hear air moving in the block. This suggests that I'm getting excessive blow by in that cylinder so I'm guessing either bore wear or piston rings.

I'm getting no unusual noises at all and no oil smoke out the back and the engine runs fine and pulls well. I do have a slightly lumpy idle though.

On the basis of this can anyone confirm my diagnosis of rings or bore wear or is there anything else I can do to test the engine. Also what could my next move be.

My engine has done 84k miles.

Apologies for cross posting this to jap.

Thanks,

Mark

[parody]

Defiantly sounds bore or ring related. I'd hazard a guess at rings as its come on suddenly, usually with bore wear all cylinders wear at similar rates so I would have expected generally low compression on all cylinders rather than just one cylinder being down.

Sounds like its time to open her up and have a look!

[dern]

parody said:

Defiantly sounds bore or ring related. I'd hazard a guess at rings as its come on suddenly, usually with bore wear all cylinders wear at similar rates so I would have expected generally low compression on all cylinders rather than just one cylinder being down.

Sounds like its time to open her up and have a look!

I think you're right. At least it'll cost me nothing but time to take the motor out and if it is rings I might get lucky and just be able to overbore and replace the rings.

[parody]

dern said:

parody said:

Defiantly sounds bore or ring related. I'd hazard a guess at rings as its come on suddenly, usually with bore wear all cylinders wear at similar rates so I would have expected generally low compression on all cylinders rather than just one cylinder being down.

Sounds like its time to open her up and have a look!

I think you're right. At least it'll cost me nothing but time to take the motor out and if it is rings I might get lucky and just be able to overbore and replace the rings.

I've had to do rings twice on a Mini before and they did no damage to the bores, so you might get lucky. I replaced them, got the bores honed and all was well.

Good luck with striping it down.

[stevieturbo]

You have melted a piston.

[dern]

stevieturbo said:

You have melted a piston.

I was talking to API this morning and that was their belief too caused by a failure of the maf. I'm taking the engine out today and have ordered a replacement from them. The difference between the replacement and the parts to fix mine weren't that great and although I'd have ended up with a 'newer' engine I haven't done an engine rebuild before and this isn't the time to learn.

[stevieturbo]

Dont forget to sort the problem that led to the damage in the first place. Dont just take for granted it was a faulty airflow meter ( although on a 99/00 car, its a 99.9% certainty is is the problem. )

[GavinPearson]

stevieturbo said:

Dont forget to sort the problem that led to the damage in the first place. Dont just take for granted it was a faulty airflow meter ( although on a 99/00 car, its a 99.9% certainty is is the problem. )

I couldn't agree more.

If one of the sensors goes down on a vehicle generally the ECU infers a value to keep the engine running, and it may well have not had other reliable signals from other sensors to infer a correct value.