12v crankcase vacuum pump

[SwissDave]

First post from a long time lurker!😄
Hi all, I have turbocharged an engine that wasn’t originally and am suffering from oil seeping past the front crank oil seal. I suspect this is due to increased crankcase pressure although I have fitted an extra breather to the block and so I would like to fit a vacuum pump to this breather to help the engine generally with increased ring sealing and to hopefully cure my oil leak. The engine is a 1690cc cross flow Renault. Any suggestions welcome, probably want about 15” Mercury vacuum and I’d like a 12v pump for simplicity. Th

[LarJammer]

Firstly you need to rig up a vacuum gauge to the crankcase to see what pressure you actually have. If you are seeing excessive pressure then its common to increase the size of the breather orifice, i have never heard of someone adding a pump to combat it...

[stevieturbo]

SwissDave said:

First post from a long time lurker!??
Hi all, I have turbocharged an engine that wasn’t originally and am suffering from oil seeping past the front crank oil seal. I suspect this is due to increased crankcase pressure although I have fitted an extra breather to the block and so I would like to fit a vacuum pump to this breather to help the engine generally with increased ring sealing and to hopefully cure my oil leak. The engine is a 1690cc cross flow Renault. Any suggestions welcome, probably want about 15” Mercury vacuum and I’d like a 12v pump for simplicity. Th

"Extra breather" is meaningless, the engine needs whatever breathing it needs........"extra" could be as small as a pinhole....or a leak via the seal would be extra lol
So exactly what breathers do you have, where, what size ? Its a small engine so wouldnt need loads unless there is a build problem.

If that is the only place leaking....then more likely is a faulty or damaged seal, or misalignment with seal and pulley or whatever is in there.

And chances of a 12v pump being enough is slim....such vac pumps are usually engine driven and you will need excellent oil/air separators so you dont end up pulling all the oil out of the engine with one.

[SwissDave]

Thanks for the replies. The original breather is a 14mm outlet from the rocker cover plumbed into the air filter.
I have fitted an extra 14mm breather to the side of the block. Both this and the original outlet currently feed to an air oil separator and then to atmosphere.
From the replies I see that I have stumbled into a realm beyond my knowledge, a little further research has thrown up another issue with an electric pump in that it would need to pull a hell of a lot more air at max revs than at say 1000 rpm. I think I’m probably over complicating thinks and that my leak may be down to a simple issue such as an imperfection in the surface of the crankshaft pulley that the oil seal contacts so I will get another one, polish the surface and I think I will try to find a better multi-lipped oil seal. Any ideas where to try for that?

[anonymous-user]

Have you got any Crank Case Breather connected to the inlet anywhere?

Turbo engines need a one way valve adding to stop the positive manifold pressure from pressurising the crankcase!

Most turbo cars have a "make up air" breather from the intake, post filter but pre-compressor to act as the secondary breather under "on boost" conditions, when the primary breather (into the inlet manifold) is blocked by the one way valve) That make up air line often also include a pressure control valve that prevents excessive negative pressure on the crank case during over-run conditions (ie closed throttle at high engine speed)