Oil catch can

[rodpaslow]

I have viewed several on here and on line - I have 1 question.  Why do almost all have a breather to the valve cover or block?  Most show a breather feeding the engine(from intake or separate little filter) and the oil catch can is separate allowing the blow by and other thought pcv an being pulled by vacuum back into the intake.  Does a diesel need that breather?  My current setup on my older car goes from the puck to the provent or catch can back into the intake.  Am I missing a breather that should be somewhere in the valve cover?  I'm planning o adding one to my TDI, but I'm not sure how to do it properly?

[RunninWild]

Its to tell exactly what your asking. Yes the system does need to vent the blowby gasses and oil vapour. If not it would create excessive pressures inside your block and blow out your seals.

The hose on top of the valve cover functions similarly to a pcv valve although I don't think it is considered one. It has the same job to vent blowby and crankcase vapours back into the intake. The system with 2 hoses I believe is a more current design feeding the block and intake. I believe the 2 hose system has an oil separator draining the oil back to the block while letting the blowby vent into the intake. On the older 1 hose system you could install a inline catch can if your worried about oil getting into your intake. There is also a small inline heater meant to help keep the oil as a vapour so it doesn't liquify if I remember correctly.

[RunninWild]

But the vent is necessary correct you wouldn't want to plug the hole and seal the system? You could technically put a small filter on the valve cover and be fine, but the filter would probably get clogged with oil over time. A catch can with a filter wouldn't be a bad idea.

[rodpaslow]

I plan on adding one to my ahu/1z tdi.  It has a single outlet currently-  hoses/lines from block and valve cover to intake(factory one).  So if a vented catch can is added that would allow for blow by to be removed and provide no resistance to air moving back into the block should it need to, correct?

[RunninWild]

No I don't think you would have any problems going that route.

[rodpaslow]

The older car I have blew the inlet line (-10°c or so) and reved upwards of it's limit till i could put the car in gear and kill it.  I hope that the fuel was somehow getting into the intake adding the extra revs and not a run-away.  Can this hurt anything?

 I couldn't test it because something happened to my starter and all it does now is turn, won't engage.

Thanks

[RunninWild]

A run away can blow the engine but if it didn't blow and you killed it with the clutch I don't see why it would have caused any damage. Unless enough fuel got in to hydroloc a cylinder.

[rodpaslow]

I'll report when it's fixed.  hoping to fix the starter, bought a new one just encase I can't.  Starter had a hard life so far, I had a 3 notch head gasket and I pulled the head mid summer and found it needed a 1 notch.  Starts much better in cold (-10 to -15 no problems cold).  Will report back to see if it's back to normal..