300 Tdi valve sealing (or not)?

[markyc]

Ladies and Gents,
Engine running, oil filler cap off, hand over filler hole and I can feel pressure building up. Is this normal? I'd guess not and go one further and guess that the valve stem seals are not doing their job. But I could be wrong; it's been known to happen before!

Ta,

Marky

[bee utey]

Valve stem seals aren't fitted to keep pressure in. They keep oil from pouring down the valves. I would look for clogged breathers first.

[RR P38]

More likely it is blow by. Some is normal.
This is just air escaping past the piston rings as the little explosion happens on the other side of them.
Yes i agree you could well have some blocked breathers.
Clear them as soon as you can and you might notice that the engine doesnt loose so much oil on the ground.

[rover-56]

I think the brake vac pump blows into the crankcase? try checking the breather cyclone and hoses.
Terry