20 replies to this topic

[coopdog]

background info: have a turbo mini which is leaking oil out the turbo, thinking it may be excess crank pressure

 

i got it running and at about 1500-2000rpm to check the blowby,
i didnt get it completly up to temp had it halfway up to temp and the oil pressure was 60 psi, i checked how much crank pressure there was by taking the rocker cap off and held my hand over it and it was like someone was blowing on my hand decently hard.

im guessing it shouldnt be like that?

 

[sledgehammer]

what pressure is the max boost pressure ? waste gate working ok ?

 

what cc , how many miles since rebuild ?

 

suck thru or blow thru

 

what vents are there & are they known to be clear

 

is it burning oil / leaking from any where else

 

where is it leaking from in the turbo area - the drain pipe

 

wild guess - rings - vent blocked - or wastegate sticking or restricted oil drain from turbo causing oil build up

 

but only a guess

 

older turbos do have slightly higher blow by due to higher pressure in the cylinder

Edited by sledgehammer, 20 December 2014 - 07:03 PM.

[coopdog]

what pressure is the max boost pressure ? waste gate working ok ?

 

what cc , how many miles since rebuild ?

 

suck thru or blow thru

 

what vents are there & are they known to be clear

 

is it burning oil / leaking from any where else

 

where is it leaking from in the turbo area - the drain pipe

 

wild guess - rings - vent blocked - or wastegate sticking or restricted oil drain from turbo causing oil build up

 

but only a guess

 

older turbos do have slightly higher blow by due to higher pressure in the cylinder

 

 

the blow by is constant even off boost.

 

its turbo....... there is only one type :L

 

havent driven it enough to check boost psi.

 

but it only has the one breather and thats on the tappet chest.

when i rebuilt it and had it on the rolling road NA it had the same problem with blow by, and that burnt no oil or had any other problems and that put out 64bhp, its weird.

 

 

and its leaking out of the turbo seals itself

[lsto]

What sort of miles has it done since you rebuilt it? I guess you checked the breathers aren't blocked, what have you got the tappet breather venting to?As for the turbo leaking does the engine spend a lot of time idling or does it do it under load and driving normally?

[timmy850]

what pressure is the max boost pressure ? waste gate working ok ?
 
what cc , how many miles since rebuild ?
 
suck thru or blow thru
 
what vents are there & are they known to be clear
 
is it burning oil / leaking from any where else
 
where is it leaking from in the turbo area - the drain pipe
 
wild guess - rings - vent blocked - or wastegate sticking or restricted oil drain from turbo causing oil build up
 
but only a guess
 
older turbos do have slightly higher blow by due to higher pressure in the cylinder

 
 
the blow by is constant even off boost.
 
its turbo....... there is only one type :L
 
havent driven it enough to check boost psi.
 
but it only has the one breather and thats on the tappet chest.

when i rebuilt it and had it on the rolling road NA it had the same problem with blow by, and that burnt no oil or had any other problems and that put out 64bhp, its weird.
 
 
and its leaking out of the turbo seals itself

There isn't just one type of turbo intake type when using a carburettor to fuel an engine...

"There are two types of choices in a carburetor turbo setup: Suck-through or Blow through. The Suck-through (or draw through) setup involves mounting the carburetor before the turbo inlet (usually in front of the impeller mouth). This means that both fuel and air are drawn into the turbo already mixed and then blown into the inlet manifold. This is by far the simplest way to set up a turbo, as the carburetor doesnt need to be especially modified and tuning is quite easy. The main disadvantages are that you cant use any intercooling with such a setup, as it is dangerous to run air/fuel mixture through an intercooler core. The reason for this is that fuel can condense inside the intercooler core and stay there if you then have an engine backfire the intercooler can explode. As a result water injection is about the only option for cooling the charge air with this setup. This also corresponds to a blow-off valve because instead of just venting pressurised air, it would be releasing a fuel/air mixture which is very dangerous. The Blow-through arrangement, logically enough, means the carburetor is mounted after the turbo compressor, so the turbo only draws in air and then blows it through the carburettor, which adds the fuel. To use a carburetor this way it has to be specially modified so that the jets will still add the right amount of fuel. This means specially sealing the carburetor and pressurizing the fuel bowls to match the turbo boost. The good thing is than an intercooler and also a blow-off valve can be used with such a setup."

[sledgehammer]

the blow by is constant even off boost.

 

its turbo....... there is only one type :L    ????

 

havent driven it enough to check boost psi.

 

but it only has the one breather and thats on the tappet chest.

when i rebuilt it and had it on the rolling road NA it had the same problem with blow by, and that burnt no oil or had any other problems and that put out 64bhp, its weird.

 

and its leaking out of the turbo seals itself

 

most mini's are blow thru turbo's like the metro - some homebrew ones are suck thru (rarer - but usually more room behind engine)

 

is it a 998cc - tappet chest vent - or a cooper engine (usuall 1275's don't have tappet covers)

 

sounds like the turbo seals are fubar

[coopdog]

 

the blow by is constant even off boost.

 

its turbo....... there is only one type :L    ????

 

havent driven it enough to check boost psi.

 

but it only has the one breather and thats on the tappet chest.

when i rebuilt it and had it on the rolling road NA it had the same problem with blow by, and that burnt no oil or had any other problems and that put out 64bhp, its weird.

 

and its leaking out of the turbo seals itself

 

most mini's are blow thru turbo's like the metro - some homebrew ones are suck thru (rarer - but usually more room behind engine)

 

is it a 998cc - tappet chest vent - or a cooper engine (usuall 1275's don't have tappet covers)

 

sounds like the turbo seals are fubar

 

 

 

nah its no the turbo seals, been rebuilt once and checked another time, turbo is fine.

all ive asked is about the crankcase pressure nothing else.....

yeah and its a 988cc, the only breather i have is the tappet cover (thread topic states 998 ;) )

Edited by coopdog, 20 December 2014 - 08:57 PM.

[coopdog]

What sort of miles has it done since you rebuilt it? I guess you checked the breathers aren't blocked, what have you got the tappet breather venting to?As for the turbo leaking does the engine spend a lot of time idling or does it do it under load and driving normally?

 

a couple of thousand since the rebuild,

took it off the road to add the turbo, ive driven it down the lane and back and got it on boost twice. thats it, it wasnt leaking got it on boost and it smoked loads coming off boost and then started leaking.

it leaks all the time, atm its spent most of its time idling.

only does it though when the engine is up to temp

 

Edited by coopdog, 20 December 2014 - 08:56 PM.

[sledgehammer]

Didn't see the 998 bit , Doh

 

IMHO I can't see blow-by causing the oil leak , on a turbo oil seal , they should be able to hold quite a few PSI

 

where have you fitted the breather pipe ? - before the turbo or after ?

 

or the drain is restricted in some way

 

does it still leak if you vent the fumes to air - so no blow-by pressure ?

Edited by sledgehammer, 20 December 2014 - 09:16 PM.

[lsto]

We have a few vehicles at work, all beit turbo diesels, and over the years on a couple of vehicles I have seen it where the turbo leaked oil when idling for a long period of time, but under normal use it clears and is fine. Smokes a bit while it brns off the excessive oil but once its in use no problems at all. I remember this because on one vehicle the turbo was replaced to try and cure the fault but the same thing happened when it idled for a long period of time with the new turbo.

If it does not burn oil as you say I'd be tempted to take it for a long run and just see what happens during use.

As for the crankcase pressure, check your breather is clear, maybe try a compression test wet and dry just to see if there is a fault with the rings. Again if its not burning oil I wouldn't worry unless the results are excessive then maybe a hone would help. Could even be a damaged ring but I would expect smoke.

[coopdog]

Didn't see the 998 bit , Doh
 
IMHO I can't see blow-by causing the oil leak , on a turbo oil seal , they should be able to hold quite a few PSI
 
where have you fitted the breather pipe ? - before the turbo or after ?
 
or the drain is restricted in some way
 
does it still leak if you vent the fumes to air - so no blow-by pressure ?

It's venting to air just to see if I Can reduce the pressure, but like I said I have just the breather and it isn't blocked,

The way I'm looking at it, the excess crankcase pressure is stopping the oil drain properly into the block because pressure is pushing it's way back up the oil drain stopping the flow, so the the turbo is just filling up and oil is pushing it's way past the seals :/

[coopdog]

We have a few vehicles at work, all beit turbo diesels, and over the years on a couple of vehicles I have seen it where the turbo leaked oil when idling for a long period of time, but under normal use it clears and is fine. Smokes a bit while it brns off the excessive oil but once its in use no problems at all. I remember this because on one vehicle the turbo was replaced to try and cure the fault but the same thing happened when it idled for a long period of time with the new turbo.

If it does not burn oil as you say I'd be tempted to take it for a long run and just see what happens during use.

As for the crankcase pressure, check your breather is clear, maybe try a compression test wet and dry just to see if there is a fault with the rings. Again if its not burning oil I wouldn't worry unless the results are excessive then maybe a hone would help. Could even be a damaged ring but I would expect smoke.

Yeah it is weird, no burning oil at all until the turbo kicks in and starts leaking.

Like I said it was the same when it NA and when I was at the rr he said that the valves were leaking and that's what the excess pressure is, so I had the valves lapped during this build and it's the same,

And it was putting out 64bhp NA so the excess pressure couldn't of been anything bad if it was putting out those kinds of figures haha

[coopdog]

More background info!!
.

What first happend was I got it up to temp via idling took it for a tiny drive left it in first and slowly accelerated until it started boosting, I let off and had a load of compressor surge and with that a load of smoke out of the exhaust and engine bay, drove a little but more and got it on boost one more time and it did the same pulled over and it was smoking a bit, looked underneath and it was leaking a bit got it back to the garage and took the turbo off and sent it back to the company who rebuilt it to check the oil seals and everything is spot on, put it all back together and it only leaked when it got up to temp and that's where we are now

[lsto]

I see where your coming from then. Also if you have a lot of blow by from the rings then under boost it would only make the problem worse. I can't see it being a problem with the valves, if they had that excessive leakage you'd at least be burning oil on start up.
If I was in your position I'd try a compression test wet and dry just to eliminate the rings or bore wear

[BritishRacingGreen]

What about going back to NA to see if that cures it? If it's still doing it then you can rule out the turbo, as that'll just be making it look worse not causing the problem.

The excess crankcase pressure sounds to me like the rings haven't bedded in correctly? Especially as you say the engine has spent most of it's time idling - how did you run it I'm after it was rebuilt?

Finally if your turbo is still leaking then it can only be a few things - to much oil pressure, too much oil flow, restrictive oil drain path, damage or incorrectly installed seals, worn bearings or shaft or a cracked/damaged casting.