2016 G550 32k miles.
Dealer says pressure should be negative 5-8 millibar.
current pressure is -40 millibar (this is ultimately less than 1PSI).
they claim this has caused the rear main seal to be sucked inward and to leak....is this possible? I can't imagine such a small amount of vacuum would cause a seal like that to leak?

 

So ask them there is no other place the engine could leak in air to satisfy the vacuum?
Like and open intake or exhaust valve?
PCV?
Dipstick?
Oil Fill cap?
Front crank seal?

As famed horn loaded speaker designer Mr Paul Klipsch said years ago to wild claims =
BS!

 

Can negative 40 millibar even make a seal leak? Seems like such a small amount of pressure.

 

Depends on seal, material seal is sealing, lubricated or not and with what?

But I doubt it

Hell I doubt they have a gage that accurate to record vacuum at -40mBar
Wonder what the tolerance is?
ASk them what the seal manufacture specs for vacuum are?
(yeah My guess is they do not say as they tend to worry about pressure.)
Ask them was that a GAGE vacuum or absolute?

All sounds like something someone creative came up with to either get your $$$$ or send you down the road.

Why cant they just say they have no freaking idea why main seal leaked it just happens sometimes.

 

So they are saying -40 in crankcase....caused by faulty oil seperators...left and right. They claim both failed at 32k miles. Apparently spec is -8 max in crankcase. Rear main seal is Apparently being sucked inward because of the -40 millibar vacuum. Doesn't add up to me.

 

The dealer is full of baloney. Don't take the bait and ask about whether vacuum is part of the equation. They have offered you a red herring; don't accept it.

 

Dealer is claiming it is this excess vacuum generated by the faulty oil seperators (Left and Right) that is causing the rear main seal to be suctioned inward.