307D vacuum system - PeachParts Mercedes-Benz Forum

horsebox · #1 07-11-2007, 03:44 AM

Still haven't managed to get a manual to help me through this, so maybe someone here can help again!

Could the pressure build up in the rocker box be caused by the vacuum pump? where does all the air that it sucks go? someone mentioned broken diapragms?
And are there any online engine diagrams?

I'm a bit worried about the engine running on oil mist which seems to come from the rocker box breather, and there is quite a bit of pressure build up when it's hot.

Shes starts well and runs smooth and quiet and doesn't use any oil so seems like a sound motor.

Thanks for your help, if any one needs help with a Laverda motor I can help there!

kerry · #2 07-12-2007, 08:51 PM

Most people on this board don't know much about the vans. I'm pretty sure you only have one vacuum component on that engine, the shut off valve. The vacuum pump is on the front of the engine. There are two styles, one of which has a clear plastic line running from the pump to the intake manifold or air filter. If the diaphragm fails, this line can send oil into the intake.
I doubt if a failed pump diaphragm would add much pressure to the crankcase. How much pressure are we talking about? If you remove the oil fill cap, how much blowby is coming out?
I've never heard of a 616 running of the oil mist from blowby, not that it's not impossible. On the other hand, oil being pumped into the intake from a failed vacuum pump diaphragm is not unheard of.
The later 617 engines had an oil separator which allowed the oil to drain out of the blowby and back into the pan. Perhaps installing some kind of separator in your system would solve the problem. Run the hose from the valve cover (rocker box) into the top of some kind of container (soda bottle, coffee can etc). Run another hose from the top of the container over to the intake. The oil should accumulate in the container by dropping to the bottom and the gases continue thru the hose.