Thread: Brake Servo Vacuum Pipe Connection on Plenum

I believe the black connector is the sucker for the positive crankcase ventilation system hence my comment that I thought there is a valve in it to stop oil getting in and getting into the brake booster port next to it, so stopping oil getting into the brake system from the crankcase vent system. If you ever pull the plenum off you will see how much oil and crude is in there.

Just so happens I have two of these plenums lying around so undid one of the black plastic connectors - it does not have a valve in it but it does have a restrictor about half way in - the restrictor has a hole about 3mm in diameter so catches any oil which flows back into the engine.

So the correct part will be needed as I doubt from a hardware store or Pirtek will have the restrictor in it.

Garry

I’m pretty sure there is a restrictor on the other end, at the rocker cover. Will check tomorrow as my whole engine is in bits.

This is what you are talking about

Inseret.jpg
Yes it goes in the pipe at the rocker end but in the black plastic connector that screws into the plenum, on the two I have here, there is a restrictor inside the plastic connector - it looks as it is a simple blocking plate with about a 2 - 3 mm hole in it to allow the vacuum to suck in any oil mist that gets past the thingy in the pic above but capture any oil which then flows back into the rocker cover.

Have you actually unscrewed your broken connector barb out of your plenum to see what you have or do not have in yours?

Garry

Originally Posted by biggin

There are two fittings together, one a push-in tube fitting at the front and a plastic barb fitting behind.

Like this

101

I assume you broke the black one (the one in the pic has a restrictor about half way down it) - my understanding is that the black one is the crankcase sucker and the red one is where your brake booster pipe pushes in.

Originally Posted by 101RRS

....

I assume you broke the black one (the one in the pic has a restrictor about half way down it) - my understanding is that the black one is the crankcase sucker and the red one is where your brake booster pipe pushes in.

Ah!.
My red one is installed on my 2 D2s, but I definitely don't have the barbed one.
And I must have removed the blank/end plug thingie off the small nipple down low.

Originally Posted by 101RRS

This is what you are talking about

Inseret.jpg
Yes it goes in the pipe at the rocker end but in the black plastic connector that screws into the plenum, on the two I have here, there is a restrictor inside the plastic connector - it looks as it is a simple blocking plate with about a 2 - 3 mm hole in it to allow the vacuum to suck in any oil mist that gets past the thingy in the pic above but capture any oil which then flows back into the rocker cover.

Have you actually unscrewed your broken connector barb out of your plenum to see what you have or do not have in yours?

Garry

Thanks Gary, yes that’s what I’m talking about.
And no, I haven’t unscrewed the broken bits. Will do that later today.
Whatever I find, I should be able to modify a standard fitting.

The issue is that as you can see in my pic the crankcase sucker is right next to the red brake booster port - any oil that gets sucked into the plenum (and both of mine when removed were full of it) can then work its way into the brake booster - however I did read somewhere that the designers took this into account and the booster is higher than the port so any oil that gets into the booster pipe can work its way back into the engine when shut down.

From the comments on here some of the black barb connectors do not have a restrictor in them but both of mine too - the inside diameter of the connector is about 10mm and if you look inside with it held up to the light you will see it blocked except for a smaller hole of about 3mm.

Take yours out, have a look and see - if it has a restrictor get the same, if not, likewise get what you have. If yours does not have a restrictor then any suitable connector will do - I have replaced the red one for the brakes with a simple brass connector as this red push pull things are a pain and mine was not sealing on the pipe when it was pushed in.

Good luck

Garry

Busy setting this up today and removing bell housing bolts. One to go. Will have a look soon. Stopped for a beer