pcv test, cheap catch can?

[karl210]

Im chasing a boost leak, i can hear hissing while on boost and theres an intermittent power loss. I upgraded the dv to the revision d item the other day and it pulls much better at high rpm than before but now and again its still not 100% I did the test while you let the car idle and pull the dipstick out and it idled rough untill i put it back in, suggesting my pcv is fine. I decided to remove the pcv valve block thingy and blow through the hole from the inlet manifold. If i progressively blew through it, it wouldnt fully seal but if i suddenly blew in slamming the valve shut it would hold the pressure about 95%
So does this mean my pcv valve is on its way out and explain the intermittent boost leak?
Ive got a catch can and done the pcv delete on my 1.8t. Is there any reason i cant either use this or at least use it to test if my pcv is bad?
I was thinking of taking the pipe off where the red and green arrows are and blocking the manifold with a bit of silicon hose and a bolt which i have. and then basically attaching that pipe to my catch can and venting to atmosphere? would there be any problems with that?
Or if there is will that be ok for a test run to check if thats my problem? i cant justify the ridiculous price to install a catch can on these engines when it cost my 1.8t £35 including can and hoses. Any help would be great, cheers

[GrayMK5GTI]

Venting to atmosphere will smell and fail an MOT. 

Catch cans are a waste of time on the TFSI as you will always get oil in the inlet manifold. Your best just buying the latest part no PCV and leaving it at that 

[karl210]

Everybody said about the smell when i did it to my 1.8t but i didnt notice anything, i just ran the pipe underneath the gearbox. I would change it back anyway but after reading this it looks like the best way isnt to vent atall.

Think ive found my answer. Any comments? After reading a comment at the bottom its best to plug both sides orelse it will leak in unmetered air after the maf.
http://deviantspeed.com/the-ultimate-20t-pcv-fix

[bacillus]

Catch cans are a waste of time on the TFSI as you will always get oil in the inlet manifold.

Interesting but the purpose of a catch can on this platform is to minimise the amount of volatile oil vapours that can potentially go on to cause deposits on the intake valves. No one would suggest that it totally eliminates oil vapours from getting into the inlet tract.   

[karl210]

that too but the main reason i want to do it is to eliminate it as a boost/vac leak. If i could blow through it then i wonder what 12psi of boost is doing. If i have time before work tommorow and the weather holds up i will see if i can do it and report back

[Unicorn]

Hi Karl,

yes, you can do as you say.  The PCV valve only operates during idle/low load but it's common for it to leak under boost.  Blocking off at the manifold will prevent any boost leaks.  Catch can and atmosphere won't smell much because very little breathing is done from this port.  Most of the breathing is done from the crankcase and sent back into the airbox.  If you also sent this into the catch tank then you would get the smell.

Rick

[karl210]

Thanks Rick, ive just sent an e-mail to your company regarding the price of a stage 1 remap 

[GrayMK5GTI]

Catch cans are a waste of time on the TFSI as you will always get oil in the inlet manifold.

Interesting but the purpose of a catch can on this platform is to minimise the amount of volatile oil vapours that can potentially go on to cause deposits on the intake valves. No one would suggest that it totally eliminates oil vapours from getting into the inlet tract.  

VRSAlex cleaned his inlet valves then fitted a forge catch can, within a few thousand miles the valves were covered in carbon again. Turbo engines will always get oil etc through the inlet system through the turbo so there is no way to prevent it happening. A catch can may very slightly minimise the amount, but I still don't think it justifies the outlay. Especially at £300+ for the forge one  

Also a few forum members (James being one of them) reported that the car didn't run right with a catch can. They swapped back to a PCV and all was sweet again.

I've put a lot of thought into this when I had my GTI and decided not to bother in the end. VW designed the car to run with the PCV system so it can't be all bad. . .

[karl210]

ok so this morning before work i had 20 mins spare so thought i would pop the pcv pipe off to check the diameter so i can dig some tube out or order some the correct size. Bloody hard to get off arent they so i was tugging pretty hard......    and the bloody thing snapped off!! ohhh Fu** so i had to block it there and then, luckily i had the perfect thing to hand!
Car seems to drive fine, no idling or strange running issues atall but because of the snow ive not been able to properly drive it to see the results. I logged my car only the other day so if the snow is gone tommorow or friday i will do another log and we can compare 

[Unicorn]

It'll run fine blocked off, it just means that it isn't drawing in fumes under vacuum.  If you do a lot of start stop then it's a good idea to change your oil more often.

Rick

[karl210]

yeah, i only travel 4 miles to work so it doesnt get a proper run through the week but at weekends i travel so its not too bad and I gave it a service the other day. Right after logging tonight it seems it hasnt made a blind bit of difference! but at least its sorted for peace and mind. I will definitely be booking my car in with you Rick within the next few weeks.