75 300D Vacuum problem - wet vac?! Video - Page 2 - PeachParts Mercedes-Benz Forum

kerry · #16 09-05-2011, 01:44 PM

I would not hook up the green and yellow vacuum lines until you get the slow shut off problem figured out. You'll be introducing lots of additional vacuum pods and connections into the system which will make it hard to diagnose your slow shut off. Did you measure the vacuum at the main line yet or let the engine run for a while and try to shut it off?

tomscat1 · #17 09-05-2011, 02:05 PM

Kerry,
What does that white piece in the J line look like to you? I dont have anything like that on my car, which is basically identical to Mark's.

Point taken on the other vacuum lines. It does appear that he does have the ignition shutoff valve lines correctly routed. I am curious to see how everything works now. I suspect that we are not out of the woods on this just yet.

1975300D · #18 09-05-2011, 02:21 PM

Hi Guys,

Okay I hooked it up. Now, I don't have a proper size piece of hose to go to the WW lines, so they don't work properly yet, but I was able to get washer fluid to shoot out of the hood nozzles. So, yes, somehow that set up works!

Thanks Tom, that problem was really bothering me!

I did try idling the car for about 10 minutes to see if that made any difference, but it did not. It still took 3.5 seconds to shut off.

My concern is that I will not be able to access the vacuum line connection points to test them with a gauge without taking my car apart piece by piece. Aren't many of them hidden under the dash and inside the doors? I know my automatic door locks don't work.

Mark

kerry · #19 09-05-2011, 02:35 PM

Quote:

Originally Posted by 1975300D

Hi Guys,

Okay I hooked it up. Now, I don't have a proper size piece of hose to go to the WW lines, so they don't work properly yet, but I was able to get washer fluid to shoot out of the hood nozzles. So, yes, somehow that set up works!

Thanks Tom, that problem was really bothering me!

I did try idling the car for about 10 minutes to see if that made any difference, but it did not. It still took 3.5 seconds to shut off.

My concern is that I will not be able to access the vacuum line connection points to test them with a gauge without taking my car apart piece by piece. Aren't many of them hidden under the dash and inside the doors? I know my automatic door locks don't work.

Mark

You need to check it system by system and not individual component by individual component, hence the green/yellow distinction. You can pull a vacuum on the green system and then a vacuum on the yellow system and isolate the problems to one of those two systems. HOWEVER, you have a problem which is in neither of those systems if you have shut off problems with them disconnected.

1975300D · #20 09-05-2011, 02:55 PM

Kerry, I notice that there are black, yellow and white vac lines going into the doors. The brown lines go to the shut off valve, and the green I have no idea. That might be climate control stuff.

But there must be some central reservoir right, places where these various systems draw their vacuum. If the leak is at these junctions, and these junction points are buried inside panels, I will have to take apart the car.

It would be nice if these junction points were made accessible, but they are not.

However, the shut off system should be very simple. It goes from the main line through the firewall to the switch. And from the switch back through the firewall to the fuel shut off valve. The only connections are at the switch - which are tight - and at the fuel shut off valve - which are also tight.

tomscat1 · #21 09-05-2011, 03:09 PM

W115 vacuum system diagram

w115 1976 300d vacuum diagram help

Here are a couple of links re: w115 vacuum. They may not be of much help.... However they do refer to the vacuum diagram sticky in this forum, and also to the gas engine counterparts of the w115. You never know, you may find something useful in any of those.... And it is a place to start.

If you haven't already, you may want to invest in a MityVac, or similar item. Harbor Freight sells a cheaper version.

What are you using as a reference manual? You should have something.

http://mercedesdieselrebuildingdiederich.blogspot.com/2011/05/service-manuals-for-mercedes-w115-300d.html

A pack of golf tees may also come in handy for isolating the lines. Kerry is absolutely correct: the key is to check the vacuum lines systematically, not scattershot.

I am told that the door lock failure is often due to deteriorated diaphragms in the individual doors. It may be one or more. Isolating each one in turn may lead to the culprit (s). I haven't done this procedure, but I think others in here may have.

Glad to hear the WW system seems to have been sorted out.

Damn the torpedoes! Full steam ahead!

kerry · #22 09-05-2011, 03:24 PM

You're getting way ahead of yourself. First you need to measure the vacuum at the main line, and if that is adequate, measure the vacuum going to the shut off valve with the engine running and key in the off position. Report back the results.

1975300D · #23 09-05-2011, 04:11 PM

Quote:

measure the vacuum going to the shut off valve with the engine running and key in the off position

The problem is that there is only 3.5 seconds of that. lol. Not enough time to take a measurement.

1975300D · #24 09-05-2011, 04:26 PM

Quote:

HOWEVER, you have a problem which is in neither of those systems if you have shut off problems with them disconnected.

That's the problem. How do I locate where those systems start and end? I have yellow lines going into the engine bay, I have them going into the doors and I can't see where they meet.

kerry · #25 09-05-2011, 04:29 PM

Quote:

Originally Posted by 1975300D

The problem is that there is only 3.5 seconds of that. lol. Not enough time to take a measurement.

Unhook the line from the shut off valve with the engine running. Put a Mity Vac or vacuum gauge on the line and turn the key off. The engine will continue running and you will get a vacuum reading.

kerry · #26 09-05-2011, 04:30 PM

Quote:

Originally Posted by 1975300D

That's the problem. How do I locate where those systems start and end? I have yellow lines going into the engine bay, I have them going into the doors and I can't see where they meet.

I don't believe you have any yellow vacuum line going into the engine bay. You have yellow vacuum lines exiting the engine bay. That's why I said don't hook them up.

kerry · #27 09-05-2011, 04:31 PM

Quote:

Originally Posted by 1975300D

That's the problem. How do I locate where those systems start and end? I have yellow lines going into the engine bay, I have them going into the doors and I can't see where they meet.

All the systems start from the main vacuum line going from the pump to the brake booster.

1975300D · #28 09-05-2011, 04:36 PM

Quote:

You have yellow vacuum lines exiting the engine bay.

If you look at the video I posted, you can see there are two vacuum lines coming from under the fender and joining up and going into the main line. One is yellow and one is green. They also route back into the firewall again before that point.

1975300D · #29 09-05-2011, 04:38 PM

Quote:

All the systems start from the main vacuum line going from the pump to the brake booster.

Right, they start there, but where do they end? I can see vacuum lines inside the dash, under the kick plate running by the steering wheel shaft, I can see them going into the doors. Don't I have to test where they end to check for vacuum?

kerry · #30 09-05-2011, 05:19 PM

Quote:

Originally Posted by 1975300D

Right, they start there, but where do they end? I can see vacuum lines inside the dash, under the kick plate running by the steering wheel shaft, I can see them going into the doors. Don't I have to test where they end to check for vacuum?

No you test where they begin. You put the Mity Vac into the line where they begin and pull a vacuum. If it holds the system is fine. If it leaks, you move downstream to the next test poing.