Turbo cause loss of oil pressure??

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bzrse7en
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Turbo cause loss of oil pressure??

Post by bzrse7en » Sun Nov 20, 2016 11:58 am

Hi
What are the chances a stuffed journal bearing turbo can cause a large oil pressure drop, but not smoke out the exhaust?

I am having oil pressure issues (it has dropped to zero when running) but only when it has been given an absolute boot full to red line a few times after about an hours drive, so turbo is getting extra hot.
Gauge prob isn't totally accurate, but engine develops a top end rattle when it's down to about 10psi, so it isn't the gauge.
Cold pressure is excellent, 30 psi idle, 70 psi 3000 rpm
Hot oil pressure (1/2hr running) about 20 - 60 Coolant temp 85-95c
It will idle all day with 15 psi and with temps up to 110c.

It did it a couple of weeks ago, so changed filter and oil (synth 10-40), but no real change.

If you have seen my build diary, I took the sump off before installing the engine and the oil pickup was pretty much blocked with $hit, so engine has been starved of oil in it's life. The bearings were all good however, and the engine doesn't knock / rattle. I wonder if that problem has killed the turbo, but just starting to show now as all the sludge has been flushed out of it.

Any thoughts?

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7ish
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Re: Turbo cause loss of oil pressure??

Post by 7ish » Sun Nov 20, 2016 2:58 pm

Have you got a flow restrictor in the turbo oil feed?
7ish

bzrse7en
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Re: Turbo cause loss of oil pressure??

Post by bzrse7en » Sun Nov 20, 2016 4:59 pm

7ish wrote:Have you got a flow restrictor in the turbo oil feed?
No, however the plumbing is OEM, so doubt that is the issue.

Maybe it isn't the turbo at all, here is where I'm at:
1.8T do have oil pressure probs because of the extended service intervals, a small oil pick up and cam chain tensioner bits getting sucked into pump pick up.
It has only done 450 miles since I cleaned it all out.
The oil pump had bugger all wear, so went back in.
I could have left the pump bolts loose, but unlikely
The pump could have a damaged drive gear or have a slipping press fit gear, but no known probs. on the net
There could be a bit of gasket sealer blocking a gallery on the filter housing - maybe, but that would effect it all the time.
I put in a windage tray, that could hold the oil up as it returns to the sump.
However, the windage tray comes from a TDi VW engine from same family, so unlikely.
Gauge could be wrong when it gets hot, maybe but engine rattles when pressure is low.

The only other mod I have made involves the PCV valve plumbing and I have read this can effect oil pressure but not much info and I am not yet convinced.
This mod, which is pretty common on vw audi forums involves removing some of the crappy plastic plumbing which fails (which I didn't get with the engine anyway). The crankcase is vented to the air cleaner thru a PCV valve, which is the venting when in a boost state, the bits removed are a check valve and plumbing into the inlet mani when the engine in a vacuum state. I'm going to vent to atmo and give it a try.

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7ish
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Re: Turbo cause loss of oil pressure??

Post by 7ish » Mon Nov 21, 2016 3:50 pm

It's unlikely that the turbo bearing would be able to leak that much oil without spilling into the exhaust as the shaft play would damage the seals.. Can you feel any play on the turbine wheel/ compressor shaft?
7ish

bzrse7en
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Re: Turbo cause loss of oil pressure??

Post by bzrse7en » Mon Nov 21, 2016 4:58 pm

7ish wrote:It's unlikely that the turbo bearing would be able to leak that much oil without spilling into the exhaust as the shaft play would damage the seals.. Can you feel any play on the turbine wheel/ compressor shaft?
There is (was the last time I checked) a bit of end float, but not much. It didn't strike me as stuffed.

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feckn7
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Re: Turbo cause loss of oil pressure??

Post by feckn7 » Mon Nov 21, 2016 6:09 pm

lots of info on Audi 1.8t oil pressure issues here http://www.audizine.com/forum/showthrea ... ooting-DIY

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nz_climber
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Re: Turbo cause loss of oil pressure??

Post by nz_climber » Mon Nov 21, 2016 6:42 pm

Sounds to me like the pressure side of the system seems to be working but the supply side is failing under heavy load. Here are some ideas on what I think could be causing is. I can't remember if you changed the sump or pick up at all so some might not be an issue.

Part Blocked Oil Pick Up
Oil Pick Up in the wrong place (to close/to far from sump) (if not original pickup and sump)
Not enough baffling in the sump (causing the pick up to suck air under acceleration as all the oil heads backwards)

or the oil is not returning to the sump quick enough with some causes being
- Too much crankcase pressure / blowby causing oil to hang up and not return to the sump
- Windage tray blocks drains from head etc
- Oil returning to sump is too frothy
- Not enough Oil in the system

Anyway that is just some general ideas I had, but I have no idea about the engine type in question, but that link above seems to have some good information. Good luck finding the issue soon before it turns serious!

bzrse7en
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Re: Turbo cause loss of oil pressure??

Post by bzrse7en » Mon Nov 21, 2016 8:48 pm

I might have found it, maybe
The PCV valve sounded like it has a shuttle valve sort of thing in it as it rattled. Turns out that rattle was a large and solid piece of carbon, about 16mm in diameter which had to be broken up to get it out. The Valve has 19mm hoses but necks down to an 8mm hole, so could easily get blocked in the right circumstances.
With the theory that too much crankcase pressure will inhibit the oil flowing back from the head and turbo.
The oil drain back from the head is clear.

bzrse7en
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Re: Turbo cause loss of oil pressure??

Post by bzrse7en » Mon Nov 21, 2016 8:50 pm

feckn7 wrote:lots of info on Audi 1.8t oil pressure issues here http://www.audizine.com/forum/showthrea ... ooting-DIY
Yea, seen all that, engine had all those problems but was cleaned out ages ago.

bzrse7en
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Re: Turbo cause loss of oil pressure??

Post by bzrse7en » Sat Nov 26, 2016 9:04 pm

Well, checked just about everything on the outside of the engine, no smoking gun.
PCV system is now as clean as a whistle. Pressure Gauge is not faulty. The head return galleries are clear - there are 5, so unlikely to be blocked anyway.
This morning cold oil pressure wasn't as high as normal and it was moving up and down 10 psi, like the pressure relief valve is floating. I took off the oil filter housing, blew compressed air into the galleries and back thru the pump. Re started it and pressure went up to 80 psi, normally it has been about 70. I figured I had fixed it. However once warm and with some spirited driving (not aggressive) the pressure dropped off. You can see it drop slowly straight after giving it the boot when hot. Pressure dropped to 10 at idle and 25psi at 3000rpm. Letting it stop and cool for 5 mins and the pressure comes up another 5 psi, but drops back soon after. on hot start up, the gauge overshoots, then drops back.
A mate kept saying it could be the pressure relief valve and I dismissed this (only because it is hard to get to), seems he might be right.

Here are the photos of the windage tray and baffle, I cannot see any issues with them... maybe I'll open up the holes below the big ends.
Image
Image

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