After a run, my engine oil dip stick is often pushed up slightly, with the sound of air being sucked/blown past it.
Is this down to crankcase pressure? Too much/too little? Engine is quite oily, but doesn't seem to leak when standing.
Would a cpd help matters, or a replacement breather?
Need I worry about it at all?

Cheers

Rumble

Aidan, I think Max's red Special had that issue and it killed the engine I'm sure I've heard it's due to crankcase pressurizing so you do need one of those CPDs.

Assuming that's the problem, you don't 'need' one of those cpd things, a new breather will do the same thing.

My blue one did this for a bit . I tried another dipstick, and it was then fine for ages. Then it started again (and on the Sweden trip I held it in with a cable tie), but since I changed the rings it's been fine.

I think I've got a spare breather in amongst the junk. It's going to be way over the 5 year life span that Ecas suggest - but then so's the one I've got on.
The choices seem to be: Ignore it, try an old breather, try an inline cpd, try a new pattern part breather, or try one of those fancy new fangled breathers.
I'll have a fiddle on monday and see what I can do.

btw Anyone tried one of those breathers? At the best part of £100, it's not going to be an impulse buy.

Rumble,
have you checked the crankcase vacuum yet?
If you have, did you check it at high rpm as well as at tickover?

It's also worth checking that the rubber seal at the top of the dipstick isn't worn.
I've had to bin some where the little 'fins' which form the seal and help keep it in place had almost disappeared...

ken.

How do you check the crankcase vacuum Ken?

harry,
1.5 metres or so of 3/16"/5mm ID windscreen washer tubing, some insulating tape to wrap round one end of the tubing to make a good seal with the dipstick tube, plus enough LHM to fill about 150mm length of the tubing and you're in business.

Some folk fasten the tubing onto a board in a 'U' shape, but I tie wrap it onto a road pin, which can be stuck into the ground in front of the car.

Here's the physics bit...
< http://images.google.co.uk/imgres?imgur ... s%3Disch:1 >

With the engine running, remove the dipstick and push the wrapped end of the tubing into the dipstick tube.
At tickover, the LHM in the 'engine' side of the tubing should be about 60mm higher than that in the 'free' side and with the engine at high rpm, it should not go past 'level' in the other direction.
The reason for using a water manometer is that the vacuum or pressure being checked is quite low, with 50mm water gauge being only 0.07 psi.
The 'free' leg of the manometer should not be sealed, but must be open to atmosphere, btw.

Fwiw, all of the engines/breather combinations in our cars go 'slightly' positive at high rpm, but since the engines don't leak oil, don't blow their dipsticks out and don't seem to be lacking in performance, I'm leaving things as they are...

ken

Edit: Apologies, originally put 5mm OD tubing, when it should have been 3/16"/5mm ID.
This has an OD of about 8mm, so only a few turns of insulating tape are needed to make a good seal in the dipstick tube.

Thanks for the technical advice ken - but I have a feeling that a worn dipstick may be barking up the right street. must go and check.

I've got a spare breather and a dipstick, so will have a play on monday.

Can't believe people are talking about you and dip stick in the same thread