7 replies to this topic

[cthomas443]

I have a mk4 astra sri turbo that put check oil level on mfd, before topping it up the dump valve was covered in oil (dump valve is bypassed), the boost pipe had oil all the way up to the top hat, none of the breathers are blocked and theres a very light smear of oil in the intake pipe leading from the cdti air box to the turbo as you'd expect. I've heard valve stem seals are common weak point on z20let, how can i check its not them (compression test?) before i buy a new turbo. What readings should i get with good seals?

[Nev]

I'd try posting that again in English and then maybe we could have a go at diagnosing you problem. BTW, I doubt very much you have a 'dump valve' installed, if you did your car have one it would barely idle. Perhaps you mean a bypass valve?

[cthomas443]

Really, It has a baileys dump valve on the hard boost pipe going up along side the engine to the top hat, when i say bypassed i mean its had the small pipe removed so it dont get that chav whootish noise. That pipe has oil inside leading me to think the turbo seals have gone but wanted to check if theres a way of checking if its the valve stem seals first as i've heard these are a weak point on the z20let. The cars done 120k if that helps.

Edited by cthomas443, 16 July 2012 - 08:50 PM.

[Nev]

Does your Bailey valve have a 1" pipe leading into it and a 1" pipe feeding back into the inlet tract? The only oily thing "up-stream" of your dump/bypass valve is the turbo, so it is very likely to be the turbo seals. If it were your stem seals that were leaking, they'd leak into the bores or at worst leak vapour back into the inlet plenum, so the problem is almost certainly your turbo IMO (at a guess). Luckily in an Astra the turbo is nice and easy to get to at the front of the engine bay

Edited by Nev, 16 July 2012 - 09:16 PM.

[starlight]

If the oil is in intake tracts before the cylinder head, it is far more likely to be the turbo oil seals. There will be some oil from crank case breathing in the intake system. Oil from valve stem seals will go straight down the valve and sucked into the combustion chamber.

[SteveA]

Keep in mind that a small amount of oil in the pipe is not unusual as the rocker breather vents into the inlet right before the turbo. I've certainly seen oil at the exit of the intercooler but only a small amount.

[JohnTurbo]

Lol, Nev its certainly not great to have an atmospheric bov on a car with a maf as you get a split second of super rich after a dump. Actually the vx isnt very dependant on the maf anyway. At most youd notice a slight unsteadyness between gears. It would idle all day! Ive had 2 cars with atmospheric bovs with mafs for my sins. Turbo shaft seals for the oil Id agree is likely.

[Nev]

BTW, I doubt very much you have a 'dump valve' installed, if you did your car have one it would barely idle. Perhaps you mean a bypass valve?

God that statement was completely wrong! I was thinking about a leak from the pipework post MAF for some reason. Appologies.