Turbo oil return question?

[Andy from the block]

The oil seal on the exhaust side of the my turbo recently began
leaking oil into the exhaust and consequently made the car to smokey
to drive (even at idle). (This diagnosis was given by the mechanic
at A Automotive, Glenfield)

He said he could replace the seal but there would not be much point
because a few months later it would leak again because of the way
the oil return was plumbed into the sump.

He thinks the oil return is plumbed to low which does not allow the oil
to flow back properly as there is oil on the other side of the return???


Here is a (crappy) picture I took and does this oil return look like its plumbed at the correct height to you guys?
I have been told it is by a mate, and he recomended I just get the seal replaced and don't worry bout what the mechanic said.

I just want to get some opinions on this before I tell the mechanic what to
do tomorow. Also, would this oil return level be ok under all driving conditions, ie: under heavy braking, downhill etc would the oil surge forward?

any feedback apprecriated.
cheers
PS: if pic doesnt work, copy and paste the address into the browser (right click, properties) thanx QikStarlie

[Ae92typeX]

Cant see the pic sorry, but the 4ages Ive seen done have them plumbed to the top part of the sump. To low and it can be an issue, but yea, pic not working for me atm

[QikStarlie]

copy and paste the link intor your browser and it works.

that elbow you have on there isnt too great, would be better if the return pipe was on a angle down to the sump, not straght down then flat. almost looks like it goes up hill to the sump in the pic, witch is bad.

[Andy from the block]

thanx for the feedback QikStarlie, yeah I think the camera might not be
perfectly level with the ground, but can't remember if it was tilting forward
or backward when I took the shot.
I got the following info from http://www.turbomustangs.com/turbotech/ ... ringsystem

Oil drain
The lubricating oil flows into the turbocharger at a pressure of approximately 4 bar. As the oil drains off at low pressure, the oil drain pipe diameter must be much larger than the oil inlet pipe. The oil flow through the bearing should, whenever possible, be vertical from top to bottom. The oil drain pipe should be returned into the crankcase above the engine oil level. Any obstruction in the oil drain pipe will result in back pressure in the bearing system. The oil then passes through the sealing rings into the compressor and the turbine.

Does the diameter of the oil return look ok to you guys?
Do you think the oil return pressure from an average turbo setup would be enough to overcome that possible slight incline in the oil return?

[jondee86]

Kind of interesting topic Here is something I found:-

The seals within the turbo are not meant to hold back a bearing housing that has become full of oil. They are designed to sling the oil mist and spray within the bearing housing away from the point where the shaft comes out each end. If the bearing housing becomes full of oil it will ooze out past even brand new seal rings.

The oil should freely drain out of the bearing housing as quickly as the engine supplies it. This is why the drain tube is so much larger than the supply tube. Gravity is the only force moving the oil out of the turbocharger. Any slight restriction in the oil drain tube, even a small silicone dingle berry, can slightly impede the draining of the oil and cause oil to back up into the bearing housing.

The crankcase vents are the second largest cause of oil loss from a good condition turbocharger. The seals in the turbocharger were designed with expectation that the pressure inside the compressor and turbine housing will always be greater than the pressure in the bearing housing. If this is ever not the case then oil will come out past the seals. A restricted crankcase vent will cause this to happen.

If the amount of ring blowby exceeds the ability of the crank vents to release the pressure positive pressure will build within the crankcase. This pressure within the crankcase can exceed the pressure inside the compressor and turbine housings under some operating conditions resulting in oil being driven pass the seals by the improperly biased pressure gradient across the seal rings.

Which explains why it is not a good idea to have the return below the
oil level in the sump. Also, if your return pipe loops down then up again
before entering the sump, the oil will form a "seal" in the pipe. This will
have the same effect as plumbing into the sump below the oil level.

Cheers...... jondee86

[evil_si]

from memory i used 3/4 hose for the drain, a fair bit bigger than the 5/8 hose alot of engine manufacturers use.
and the drain was plumbed in to as high as possible in the sump,

as i said on the phone, when i dynoed the car i had a clear hose on the drain, and i watched it to make sure there was no 'build up' of oil in the drain line,
under normal engine operation, the oil level in the sump would be under 3/4 if not 1/2, if it remained fill the oil pump certainly isnt doing its job.

from experience with working on heavy equipiment, if the drain line is restricted enough from the start, the turbo oil seals will blow pretty much straight away,

[Andy from the block]

as i said on the phone, when i dynoed the car i had a clear hose on the drain, and i watched it to make sure there was no 'build up' of oil in the drain line,
under normal engine operation, the oil level in the sump would be under 3/4 if not 1/2, if it remained fill the oil pump certainly isnt doing its job.
from experience with working on heavy equipiment, if the drain line is restricted enough from the start, the turbo oil seals will blow pretty much straight away,

Ok, I will pass that onto the garage that has the car and see what they say.
You said you watched it through a clear hose, but this was on a dyno?
Do you think if the car experienced heavy braking/cornering maybe
combined with a steep downhill angle that the line could be momentarily
blocked? What you said makes sense to me anyway, and Ive heard from
Bazda that the way the oil return is plumbed should be fine. Just wanted
to double check to make sure the new seal wouldnt have problems later
down the line. Cheers to everyone thats given me a hand with this issue.

[evil_si]

no i dont think heavy braking cornering etc will make that much difference, the sump also has a baffle inside it,

and it is a large 3/4 drain line,

the car was being pushed hard on the dyno, so if there was a problem it should have shown itself then.

a new seal on its own would be just a quick fix, it should be re bushed and balanced as well since it is being stripped.

[Andy from the block]

If the turbo has no shaft play, should it also be re bushed and balanced?

[evil_si]

personally yes, or balanced at the very least.

[1598cc]

remember oil return is done on gravity, so needs a downward slope into the sump otherwise itll bank up.