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  #1  
Old 07-07-2019, 03:33 PM
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Join Date: Jul 2019
Location: Birmingham
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Vacuum Leak Assistance

Alright one issue that is on my short list to tackle on the new (to me) 300D is finding all the vacuum leaks. All the typical issues apply, car wont shut off, door locks don't work, shockingly the windows work! Im currently having to shut the car off with a vacuum pump I have plumbed into the ignition switch hose

Im looking for some guidance on where to start? I know from having to fix the ignition key first thing when I bought the car that those lines are not the issue, I tested the vacuum created when turning the key off its only pulling about 5 PSI on my pump gauge. I assume that the leaks in other places are decreasing that pressure?

Can anyone answer which likes these are that are capped by PO? The yellow hard line broken on my driver door matches the unplugged valve in engine bay so is that the door lock vacuum line?
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1983 300D 255K
2014 ML-350 Bluetec
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  #2  
Old 07-09-2019, 11:26 PM
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Location: New Jersey
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The fellow thing with two connections on it is a check valve for the locking system - two connections is because one goes to the vac reservoir, the other to the main lock control in the front driver door.

It looks like the 4-way connector is plugged up. At that point I’d just go get some 4mm (3.5 preferably) hose and just connect the green, which is for the hvac.

Looks like you’re missing a brown one in the loop off the four way fitting that’s plugged up. The brown one goes to the ignition switch, which when manipulated shuts the car off.

Get the right brown lines hooked up to the ignition and the vac system in the right manner, and go from there. If you have hvac and shut off, it’s not right, but you’re functional.

Check the shut off valve as well. I know you said you’re shutting off with a pump, but does that valve hold vac? Is it supposed to?

The key is to systematically go through issues and repair them
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Current Diesels:
1981 240D (73K)
1982 300CD (162k)
1991 350SD (113k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)
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  #3  
Old 07-12-2019, 07:19 PM
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Join Date: Jul 2019
Location: Birmingham
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Quote:
Originally Posted by JHZR2 View Post
The fellow thing with two connections on it is a check valve for the locking system - two connections is because one goes to the vac reservoir, the other to the main lock control in the front driver door.

It looks like the 4-way connector is plugged up. At that point I’d just go get some 4mm (3.5 preferably) hose and just connect the green, which is for the hvac.

Looks like you’re missing a brown one in the loop off the four way fitting that’s plugged up. The brown one goes to the ignition switch, which when manipulated shuts the car off.

Get the right brown lines hooked up to the ignition and the vac system in the right manner, and go from there. If you have hvac and shut off, it’s not right, but you’re functional.

Check the shut off valve as well. I know you said you’re shutting off with a pump, but does that valve hold vac? Is it supposed to?

The key is to systematically go through issues and repair them
Thank you for the assistance! I’m going to order replacement for that 4 way and start by hooking everything back up and go from there. Yes all my ignition lines and vacuum shut off valve hold vacuum.
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1983 300D 255K
2014 ML-350 Bluetec
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  #4  
Old 07-12-2019, 08:13 PM
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Join Date: Jan 2002
Location: New Jersey
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I’d hold off on putting a new 4-way into service.

Get some 4mm tubing from the auto parts store. Anyplace has it. 5/32” tube should state 4mm. Find a store or use amazon and get a 2-pack of 5/32” tees as well for $2.19.

Use your new 4mm line to test just the brown shutdown circuit. Does it hold or leak? If it’s good, then you can connect just that to the main hard line and be set. But then also test the other consumers. If one or two are OK, use the tees.

After all is fixed to your satisfaction, get some 3.5mm tube from here, and the correct Y/4-way and put it all back.
__________________
Current Diesels:
1981 240D (73K)
1982 300CD (162k)
1991 350SD (113k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)
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