turbo oil supply check valve operation

b930 · 05-01-2012, 05:13 AM

Was hoping someone could describe how the simple ball / check valve in the oil supply line to the turbo works? I understand the ball floats and with pressure under it, it lift up against the lower side of the special banjo with slots in it so oil bypasses. Now with the engine off, how does the ball stop oil running to the turbo? does it just sit on the seat with gravity?

If the oil in the tank is at a higher level than the ball, will the head of oil not just push the ball off the lower seat?

Just trying to figure out how it works and what it was designed to do. I know many report of oil continuing to flow through the turbo with the engine off without the ball installed.

fredmeister · fredmeister's Garage

I think it is meant to stop oil from draining out the turbo oil supply pipe and back into the engine case via a siphoning effect.
This way the oil pipe is not bone dry on restart starving the turbo momentarily.
The oil in the sump should have no way of getting back into the case unless it works its way past the oil pump gears and even then I think it would take a while to fill the case back up this way.

Tt surgeon · 05-01-2012, 04:36 PM

where in the oil line is the ball anyway?

Ronnie's.930 · 05-01-2012, 05:03 PM

Quote:

Originally Posted by Tt surgeon

where in the oil line is the ball anyway?

It is in the fitting assembly that also incorporates the low oil pressure idiot light switch.

cole930 · 08:46 AM

The ball is a factory check valve of sorts and as Fred noted
primartly used to prevent siphoning. The ball was a stock item
in all the turbos and it's 9mm in dia. The spring is not a stock
item but is used in instances where excessive oiling is present
in the turbo. The spring is used on top the ball to adjust the
flow to a lesser amount.

Cole

Tt surgeon · 05-01-2012, 05:14 PM

Thanx

b930 · 05-01-2012, 10:06 PM

Ah right, I think I have it now. If is was to stop oil syphoning out of the oil line to prevent dry start ups of the turbo then it all makes sense. I saw some threads saying that without it the oil drip tank would full up on shut and could not work out how it prevented this, but syphoning back makes sense as it seats in the cone on the bottom side, preventing this.

Was the sping under the ball a factory fitment? That would in theory then prevent it from acting as a check valve against syphoning.

xbmwguy · xbmwguy's Garage

no thats not a factory fitment and i think cole meant "spring on TOP of the ball" to apply slight pressure to seal better.

cole930 · 05-02-2012, 08:47 AM

Thanks xbmx !!!!!

I edited my post.

Cole

b930 · 05-02-2012, 03:45 PM

Got it, cheers

sundevil64 · sundevil64's Garage

Anybody have specifics on the spring? I am having excessive oiling.

gavinc69 · gavinc69's Garage

So its like when you put a straw in your drink then put your finger over the end of the straw and lift it out, the liquid in the straw stays in it.
So when the ball bearing sitting in place is like your finger and the oil in the pipe to the turbo stays put like the liquid in the straw!

Alan L · Alan L's Garage

Quote:

Originally Posted by sundevil64

Anybody have specifics on the spring? I am having excessive oiling.

I don't think it is designed to restrict flow to the turbo. It is designed to cut off siphon supply after shutdown. Otherwise you can end up with a puddle of oil on the floor via the turbo. If you have excessive oiling (presuming this means out the back of turbo or in your intake system) more likely an issue with turbo seals. Or your scavenge system has an issue.
Alan