All,

I finally got a Mity Vac yesterday, feels like a rite of passage.
Anyway, I got as far as checking the shut-off valve, it kills the engine with just a few pumps.

Now, I am checking lines and connectors, but I'm not sure if I am doing it right:

-I check the lines with the engine off, correct?
-What kind of pressures should I be getting?

Thanks a lot!

If your checking with engine off u should be going like by line and giving it a few pumps and letting it sit a watch for pressure to leak down, if one does leak add new fresh rubber fittings down stream and re check then continue moving up stream.

Much better to just take an hour and a kit and replace all the easy ones coming out of the firewall into the engine bay.

Now when you are getting into the door locks and HVAC systems this is much more of a hassle

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Thanks, my door lock system is completely disconnected so I’m not worrying about that right now.

Today, when I tested the brown line going to the ignition I got something like 16”, then the return line from the ignition was 6”. The shut off valve worked fine.

Just about everything else was leaking. No matter what I plugged into, nothing would hold pressure. Either I’m testing wrong, or I need to replace everything. If everything needs to be replaced, I’m suprised it shuts off at all, it usually takes about 3-4 seconds after the key is turned

Wouldn't surprise me at all if every rubber fitting was leaking.

When the 3 to 4 second shut off thing happened to me I had to replace the rubber thing that's actually connected to the shut of solenoid.

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Got it, that may be what happening then. Most of the fittings slip out without much effort so I doubt they're holding pressure.

I am going to replace all the rubber bits, what size do I need? I'm seeing 3x9mm and 3.5x7.5mm on Pelican.

It should only take _one_ pump with the MityVac to stop the engine .

yes, you need to buy a HUGE roll of silicone vacuum hose, it'll outlast you and the host here has it in at least two colors, it took me a while to find it (searching "vacuum hose" doesn't work) but it's *very* good stuff .

Any vacuum hose you can disconnect without twisting and pulling hard on it, is bad and leaks .

This is a simple if time consuming testing / repair that yields large rewards you'll enjoy .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Then again it could be only one connector that is causing the problem. I think it unlikely that all of them went at the same time. I would look for a connector that is common to a lot of the vac lines. That could be your only problem. I have a '81 300SD and all of the lines and rubber connectors are original except for one behind the ignition switch that I broke futzing with it.

Start at the pump and follow the lines outwards. If you can draw a vacuum, everything is in good shape. if not, follow to the first branch, and plug branches until you find the one that doesn't hold, keep moving forward through the system.

Thanks everyone, I am just going to replace all rubber connectors and Y connectors, then see where it gets me.

Side note, there is a little vacuum port on the top of the valve cover - what does it do? In my case there are 7 holes, but only 3 are being used. It's odd.

It's used to control the EGE valve and to ensure smoother shifts for lazy American drivers .

Unless the rubber connectors are loose, leave it be for now .

In time you may or may not want to disconnect it .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Very interesting. I won't mess with the placement, but the rubber ports do feel a little loose so I wonder if they contribute to my system leak.

They should not feel loose at all.

To re iterate :

ANY vacuum connector that you can remove without twisting and pulling IS BAD AND LEAKING .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

All, I finally got my parts and worked on this today:

Replaced all rubber connectors, went for a spin. It shifts better, so that's cool. But I still have a 3 second delay on shutdown...

-Vaccum pump is putting out 21"
-Shut off valve works without fuss

The only place I am finding a leak is the VCV, but I am told that's supposed to leak...

I'm stumped! Any ideas?

(To be clear, it shifts very nicely. Just the shut-off delay. Also, my door lock system is completely disconnected)

UPDATE: I think I found the/a leak - one of the brake booster plastic nipples isnt holding vaccum. It doesn't appear broken, how can I patch this? The booster line looks fairly new (photo below)

https://imgur.com/a/OjUXRBc

I hate to suggest this but it could be the rubber connector on the ignition switch. There are two and one goes to the shut off valve. You just remove the instrument cluster to get to it. May have a slight leak there.