Catch can mysteries

[Czechmate]

Hi all,

Ive had a Mann Hummel provent 200 on my 2007 yd25 d40 for around 7-8 years.
It has as always worked as it should, i was draining out around 50ml of oil every month or two.

Then one day around a month ago, the rig started blowing lots of blue smoke out the exhaust that smelled like oil.

I checked the catch can right away and saw it was pretty full, i probly should have drained it a bit earlier.
I thought bugger it, its time to replace the filter anyway, so i bought a new filter and replaced it, along with the oil lines into and out of the catch can, which were pretty mucky.
I also gave the can itself a clean.

So when the new filter arrived, it came with a little leaflet and instructions that explained that due to new emissions laws, the pressure relief valve must now vent internally, instead of releasing through the cap to atmosphere,
The filter itself now has a valve built into the bottom of it, and the original relief valve that was built into the lid of the catch can must be removed and a blanking cap installed.

I did this and thought sweet all done no worries. I also checked some vids from reputable installers on youtube to make sure I was doing everything right.
But ever since this was done, i get some (not a lot but some) blue smoke on idle when the engine is warmed up, and now i get mainly water out of the catch can instead of oil.
Ive checked all the lines, the hose clamps, the filter installation, the catch can cap, everything i can think of, but i still get some blue smoke and mainly water out of the catch can every week or so when i check.

Ive tried taking the filter out of the catch can entirely, and that does stop the blue smoke.
But i dont want to remove the catch can so need to figure this one out.

Any help much appreciated

 

[OldManBeard]

I'd suggest not worrying about the catch can at this stage, as I suspect that is merely displaying a symptom, rather than being the cause of the problem. That water would be my main concern and may be contributing to the colour of the exhaust.

Perhaps you should temporarily eliminate the catch can altogether for now by joining the inlet and outlet houses together or, if you still have it, reinstalling the original hose. See what happens then. If all of a sudden everything is normal again then I was wrong and the catch can is the problem, in which case I'd advise checking yet again that the inlet and outlet hoses are going to the correct ports. I have seen both written instructions and Youtube videos where they get it wrong. Grab the correct instructions from here.

 

[Czechmate]

The thing worked perfectly for close to 8 years, with only the odd filter replacement.
It seems like a big coincidence that when the external over-pressure valve was changed to internal the catching water instead of oil thing happened..

If i pull the filter out, there is no water in the catch can and no smoke blown at all.
But then Im not filtering the PCV so the catch can obviously becomes redundant, the filter needs to stay in.


The weird thing is I havent changed the setup at all except replaced the filter with the new style (internal over-pressure valve) and replaced the hoses.

The videos i viewed were these. Im pretty careful about who i listen to on the internet.






I guess where the water is coming from is the first thing to establish
Im only just starting to go deep on this now im on holidays.

 

[Czechmate]

So i think i found the problem...

The inlet spigot on the catch can (where the hose coming from the valve cover enters the catch can) was crushed and deformed.
Its a genuine mann hummel, but it was 7-8 years old and i must've over tightened the hose clamp too i think.

I guess there was a pretty major leak there, and the suction from the turbo was still pulling air from the outlet of the catch can.
This must have been sucking in damp air from the engine bay around the catch can, causing water in the catch can.

And not sucking from the valve cover anymore so not de-pressurising the engine, hence the occasional blue smoke on idle..

If anyone has any other theories please weigh in

 

[tweak'e]

blockage in the breather causes crankcase overpressure which pushes oil past the turbo turbine seal and into the exhaust.
usually blowby is worse at idle due to piston rings needing combustion pressure to seal properly. hence smoke at idle.
tho often smoke is white but its probably being burnt in the cat, so you get blue/black smoke.