[Benjiman]

Hey guys,

I emptied my vacuum side catch can recently, it was less than half full and had been a few months since I last emptied it, all normal for me.

I had to remove it again today to get better access for something else I was doing and thought whilst it was removed I might as well empty it and to my surprise it was completely full!

What could cause this? A quick google suggests it could be PCV/ Sludge build-up/ Turbos/ Piston rings - walls.

I know my turbos need replacing soon as they are rattling, I already adjusted the wastegates arms around a year ago and rattling again, also I noticed some oil around one of the lines on the front turbo recently.
I have suspected my valve stem seals might need replacing as I have noticed some smoke on start up, but not sure if this was due to the turbos.
Also I have started to have to top up oil a few times between oil changes over the last 2 oil changes. Before that I might have had to top up once if that. Oil changes every 5000-7500 miles.
I plan to upgrade my turbos soon, and either whilst I am at it or before, replace my valve cover and gasket. Do the valve stem seals need to be removed in order to check whether they need replacing or not?

Is it more likely that my turbos or valve stem seals have caused this, or a bigger problem like the pistons?
Would a compression test show an issue with the pistons, or would I need a leak down test?
I don't want to upgrade turbos, replace valve cover and gasket and maybe valve stem seals only to find I have a bigger problem.

For reference car runs great, last log I did (only 2nd gear not 3rd) looked fine, although I'm not an expert. I have both low and high side cans, mileage 108000, original turbos. Index 12, up to date maintenance, walnut blasted during my ownership, will be replacing valve cover and gasket soon. MHD Stage 2+ with all supporting mods plus some other upgrades.

Note. One other thing I did at the same time as emptying the catch can the time before last was I upgraded the vacuum hose that runs over the engine to the brake booster, the one that the two cannisters and exhaust valve connect too.
Could a blockage in this, or a even a leak cause my problem?


Thanks for reading.
Kind regards, Benjamin

[BabyJesus87]

Hopefully it's not piston rings goin. What oil do you use?

[Benjiman]

I use 5w-30 Shell Helix Ultra ECT C3, I'm in the UK so the weather never really gets too hot or too cold.

I did two cold compression tests, results;
Cyl1 167/168
Cyl2 165/165
Cyl3 165/169
Cyl4 165/165
Cyl5 165/167
Cyl6 160/160
Which looks ok to me with my limited knowledge.

I checked the vac hose that I upgraded with a manometer and compared it to the original one that I replaced, readings were the same so no leaks there.

I checked vacuum at the oil filler cap, should be -17mbar but I'm only seeing -1.5mbar.

I have noticed a visible leak on the valve cover/gasket, there is oil on the boost solenoid tray.

The catch can filled up 3/4 again over the next 350 miles, I dipped my finger in it and it seemed mostly water. I stupidly poured it into my oil waste container instead of a separate smaller container to see how much oil was on top after settling.

I have done maybe 100 miles since then, I will empty it again tomorrow and this time check water to oil ratio.
I have a theory that the valve cover/gasket is leaking which is probably causing a small boost leak, but more importantly a vacuum leak when not in boost. It is my vac catch can with the issue. It has been winter and was freezing out a lot during the last two times I emptied the catch can, which probably meant there was more moisture in the air than usual. Also my oil usage does not add up with the amount of fluid in the catch can.
I think the leak is causing outside air to be sucked into the valve cover, air that was really moist, and filling the can really fast. Hopefully the leak is also the cause of the low -1.5mbar vacuum and a new valve cover and gasket will fix both issues! I think that at least 90% of the catch can contents is water. If it were piston rings I'd have thought that it would mostly be oil/fuel not water.

I have ordered a new valve cover and gasket, will do valve stem seals whilst I'm there. I got myself an air compressor in order to do the seals, I could do a leak down test now but I think if tomorrow shows that most of the contents is water and not oil then I won't bother.

I will keep the thread updated with how it works out.

[suspect]

Originally Posted by Benjiman

Cyl1 167/168
Cyl2 165/165
Cyl3 165/169
Cyl4 165/165
Cyl5 165/167
Cyl6 160/160

I think those compression test numbers are good.