'07 MCS has excessive crankcase vacuum. Spec is 15" of water and at idle mine goes off the scale (over 20). I have replaced the valve cover and the vacuum pump. Original issue was excessive noise from the vacuum pump. The new pump is much quieter, but the vacuum is still too high. Car has 19K miles and only started the noise 2 weeks ago. Since the last oil change 3K ago, it used 2 qts of oil. It has never used any oil before this oil change.

Parts girl at the dealer mentioned something about a checkvalve or something relating to the vacuum reservoir. I spent several hours on minitis.com and could find nothing on this issue. I have read all the bulletins about noise on start-up, etc and do not have a solution.

Help,

Barry

 

When is the last time you changed your air filter?

 

New filter. Fresh oil and filter. Old vacuum pump was full of oil when I took it off. Really poor design. If I rev motor, vacuum drops to about 18", but at idle it is about 20" I say about because the slack tube manomameter I use is for BMW's and the gauge only goes to 12". I can put a mark on the scale at approx 15", but 20" is only a guess.

Barry

 

Man I don't know ... High vacuum would be caused by a bad PCV valve and you've already addressed that with the new valve cover (valve in cover). New vacuum pump is done. New air filter.

Any other ideas anyone? I have a lot of engine experience but I'm obviously missing something

Could the new vacuum pump be too efficient? I would be shocked if that was the case. Bad PCV valve right from the start with a new cover? I sure hope these parts aren't that crappy!

 

Ok so first other than high oil consumption, what are your other symptoms? The vacuum pump has nothing to do with crank case vacuum. It is a mechanical pump that pulls vacuum for the brake system and the wastegate controller system. The vacuum side does not see the crank case. Actually the pump exhausts into the crank case. The oil in the pump is because the pump is oil pressure feed for lubrication and is normal to have oil dump out after removal. The vacuum pump noise you experienced before removal is from the thick steel coupler on the drive side. (loose tolerances and an overall bad design if you ask me) i posted a thread about removing my mechanical vacuum pump and using an electric pump in its place, still working perfectly by the way. The crankcase vacuum all comes from the vacuum that is pulled from the intake manifold between the engine and the butterfly on the intake manifold. Mine 07 runs a intake vacuum of 19-20 Inhg or around -10psi. Since the intake manifold is hooked directly to the rear passenger side of the valve cover I would expect it to be close to the vacuum of the intake manifold. The only thing I could think that would reduce the vacuum is the piston blow by working against vacuum. (creating pressure) At idle piston blow by should be minimal so I would expect the vacuum of the crank case to match the intake manifold. Well these are my opinions take them for what their worth.
Justin

 

ou can try catch can. Thats my next move My MCS has 58K on it and im on 2nd factory replaced motor from carbon build up from the PCV BS. My first one was right around the 23K mile mark so Thats my 2 cents on the issue.

 

I never burn oil in my R53, but when I had to switch to a high detergent motor oil for just ONE oil change I lost about a quart in 5K miles. When switched back from the Castrol to Amsoil I never lose a drop.

Did you happen to change oil brand this time around ?

Are you sure of your original figures for amount of "required" vac ? Reason I ask is that in an R53, those figures are in "normal operating range".

 

Was the parts advisor referring to part no. 6 below....cant say I have ever heard of this part having issues.

 

Elsinorej is correct. The Crankcase itself does not produce any vacuum only blowby gases. Engine "blowby" gases are introduce into the engine when air/fuel gases passes by the engine rings into the crankcase. During idle or deceleration minimum "blowby"is produced and during high acceleration produces maximum "blowby' produced in the crankcase. To mitigate the blowby gases in the crank (which is very bad for the engine) A PVC valve was added to pull a metered amount of blowby gas back into the intake and combustion chamber. During hign aceleration, high blowby gases are produced, the PVC pulls maximum amount of blowby back into the engine. If the blowby volume exceeds the PVC capacity the excess blowby is routed from a second valve cover tube that is connected upstream in the intake, close to the airfilter or the airfilter plumbing on the Mini. Thereby routes all blowby gases are routed back to the engine.
The high vacuum that you are mentioning sounds more like the intake vacuum, which is normally between 15-20 hg on a normally aspirated engine. Where exactly are you measuring this vacuum? If you are measuring at PVC valve (vacuum side) then that is the engine vacuum which is normal.

 

I do not have #6 on this motor and vacuum was measured at the oil filler cap. I modified the cap so that it would connect to the slack tube manomomiter (sp?) that we use on BMW's. I agree that the vacuum pump should have no effect on crankcase vacuum, but somehow it does. Disconnect the vacuum hose going to the brake booster and the vacuum in the crankcase goes to 12 inches of water. Connect it and it goes to 20 or more. The 15" of water was taken from a Mini service bulletin. The engine is quieter with the new pump and oil used has always been Castrol Syntec 5w50 full synthetic.

 

Hello and sorry for thread "resurrection",

i am experiencing the exact same thing. Do we have any updates on this?

Thanks.

 

WOW!!! Now that makes sense! I just put a new vacuum pump on and decided to block off the PCV hose because I think the oil is sucked out the PCV. After starting up, I opened the oil cap and it was like opening a Mountain Dew bottle. Also, I noticed that there is a large concentration of oil mist. So if there is air pressure introduced from the vacuum pump, and the oil mist is floating around, it only has one place to go...through the PCV hose and into the intake. I can see why the oil is not leaking and is being consumed.

ideally, if the vacuum side was sealed, the air would not pump into the crankcase, but even a little leak will pump up the crankcase.

Also, if you disconnect the vacuum hose, it would definitely cause the crankcase pressure to change even though the vacuum side is not directly tied in to the crankcase.