It's CRITICAL... how you set your transmission's vacuum system on your diesel MBZ... - Page 24 - PeachParts Mercedes-Benz Forum

hangit · #**346** 12-24-2007, 08:47 PM

Sam;

Please post some pics with the details of how and where you mounted the needle valves. Kudos to TheGear for thinking of this.

Could you also post some pics and details of how you installed the in line vacuum filters?

Merry Christmas.

John

jkoebel · #**347** 12-24-2007, 10:31 PM

Quote:

Originally Posted by Brian Carlton

Get rid of all the lines to and from the black box on the valve cover. Two of them go into separate "T's" on the driver's side of the engine. Just take out the T's and connect the remaining ends with a section of vacuum hose. Many times, the source of poor shifting is due to excessive leaks via the 3/2 valves inside the black box.

That's an answer I've been looking for, for a while. Remove T's that go to valve cover...connect left and right sides together.

I think one of the "T" connectors is on the IP though, I guess I can just plug the end of it up instead of trying to remove.

It'll work on my '83 with EGR, yeah?

Brian Carlton · #**348** 12-24-2007, 10:35 PM

Quote:

Originally Posted by jkoebel

That's an answer I've been looking for, for a while. Remove T's that go to valve cover...connect left and right sides together.

I think one of the "T" connectors is on the IP though, I guess I can just plug the end of it up instead of trying to remove.

You're not looking for that answer.......because it's not meant for you.

The vacuum system for the 616 is different than the 617 and, typically, you cannot remove the transmission control lines from the valve cover 3-2 switches.

jkoebel · #**349** 12-24-2007, 10:41 PM

Quote:

Originally Posted by Brian Carlton

You're not looking for that answer.......because it's not meant for you.

The vacuum system for the 616 is different than the 617 and, typically, you cannot remove the transmission control lines from the valve cover 3-2 switches.

D'oh

I'll just BB the EGR and keep at it then.

Brian Carlton · #**350** 12-24-2007, 10:52 PM

Quote:

Originally Posted by jkoebel

D'oh

I'll just BB the EGR and keep at it then.

Your 616 can be replumbed slightly to eliminate two of the lines to the plug.........the EGR controls. But, you cannot eliminate all the lines in most 616 configurations.

jkoebel · #**351** 12-25-2007, 07:33 PM

I plugged the EGR line.

Hooked a Mityvac in on a T going to the transmission line. From a cold start, slow build to 10 mmHg then steady while driving at constant speed, pressing the accelerator yielded a rapid drop to 0 (almost instantly) and then it'd build back up fairly quickly

VCV held 14 mmHg with almost no drop with the engine off; moving the rack caused instant drop to 0.

Shifts are still too early and very mushy. I am thinking the problem might lie in all the complicated stuff on top of the valve cover, maybe the lever up there is worn down in some way, its leaking internally, etc.

Brian Carlton · #**352** 12-25-2007, 07:35 PM

Quote:

Originally Posted by jkoebel

I plugged the EGR line.

Hooked a Mityvac in on a T going to the transmission line. From a cold start, slow build to 10 mmHg then steady while driving at constant speed, pressing the accelerator yielded a rapid drop to 0 (almost instantly) and then it'd build back up fairly quickly

VCV held 14 mmHg with almost no drop with the engine off; moving the rack caused instant drop to 0.

Shifts are still too early and very mushy. I am thinking the problem might lie in all the complicated stuff on top of the valve cover, maybe the lever up there is worn down in some way, its leaking internally, etc.

Disconnect the vacuum line from the transmission (you can do it under the hood). Plug the open line on the supply side. Leave the trans line open.

Take it for a drive and see what it does with no vacuum.

Report back.

jkoebel · #**353** 12-25-2007, 10:13 PM

Will do when its light again.

siral3x · #**354** 12-25-2007, 10:52 PM

Quote:

Originally Posted by Brian Carlton

You're not looking for that answer.......because it's not meant for you.

The vacuum system for the 616 is different than the 617 and, typically, you cannot remove the transmission control lines from the valve cover 3-2 switches.

Brian can you give me a quick run down because reading this whole thread got me confused!
My problem:
1.Car (85 300DT) will shift fine from 1-2 BUT will JERK BADLY from 2-3. Also downsifts from 2-1 with a BIG THUMP HORRID noise.
What should I start checking first? What are the steps here?

Brian Carlton · #**355** 12-25-2007, 11:05 PM

Quote:

Originally Posted by siral3x

Brian can you give me a quick run down because reading this whole thread got me confused!
My problem:
1.Car (85 300DT) will shift fine from 1-2 BUT will JERK BADLY from 2-3. Also downsifts from 2-1 with a BIG THUMP HORRID noise.
What should I start checking first? What are the steps here?

Disconnect the line to the modulator.

Connect the Mityvac. Pump up the Mityvac and see if the modulator holds vacuum.

If it does, then remove the Mityvac and reconnect it with a T into the modulator line so you can read it with the engine running.

Start the engine and read the vacuum at idle going to the modulator.

Report back with results.

jkoebel · #**356** 12-26-2007, 05:47 PM

Quote:

Originally Posted by Brian Carlton

Disconnect the vacuum line from the transmission (you can do it under the hood). Plug the open line on the supply side. Leave the trans line open.

Take it for a drive and see what it does with no vacuum.

Report back.

Hard and late. 1-2 at 15, 2-3 at 30, 3-4 at 60. Just as it was before I found and plugged a vacuum leak before the line that actually goes to the transmission.

So, we've determined that "no vacuum" makes it shift like it used to (****ty as all hell) and "good vacuum" makes it shift WAY too early (1-2 about 1 second after it gets gas, <5 mph, 2-3 at like 20, 3-4 at 35 or so -- and it also "slips" and revs randomly for a second then quiets down again. Never does this in the "no vacuum" condition.)

Have I narrowed it down to the modulator yet, or should I try replacing the crap on my valve cover entirely first? (3/2, levers, internal lines) they look pretty beat up.

Brian Carlton · #**357** 12-26-2007, 08:07 PM

Quote:

Originally Posted by jkoebel

Hard and late. 1-2 at 15, 2-3 at 30, 3-4 at 60. Just as it was before I found and plugged a vacuum leak before the line that actually goes to the transmission.

So, we've determined that "no vacuum" makes it shift like it used to (****ty as all hell) and "good vacuum" makes it shift WAY too early (1-2 about 1 second after it gets gas, <5 mph, 2-3 at like 20, 3-4 at 35 or so -- and it also "slips" and revs randomly for a second then quiets down again. Never does this in the "no vacuum" condition.)

Have I narrowed it down to the modulator yet, or should I try replacing the crap on my valve cover entirely first? (3/2, levers, internal lines) they look pretty beat up.

Very good.

So, we know that we can get the desired results with a vacuum adjustment.

Now, I'm not personally familiar with the 616, but we need to determine if the VCV on the IP is adjustable.

Please look at the VCV and tell me if it has a small domed cover on the forward end (closest to the radiator). The domed cover will be facing the left side of the vehicle (facing you when you're looking in there).

Nothing needs to be done with the modulator and nothing needs to be done with the 3/2 valves............just get that out of your mind completely and don't touch anything else.

siral3x · #**358** 12-26-2007, 08:43 PM

Quote:

Originally Posted by Brian Carlton

Disconnect the line to the modulator.

Connect the Mityvac. Pump up the Mityvac and see if the modulator holds vacuum.

If it does, then remove the Mityvac and reconnect it with a T into the modulator line so you can read it with the engine running.

Start the engine and read the vacuum at idle going to the modulator.

Report back with results.

Is the modulator the white piece on the IP?

Brian Carlton · #**359** 12-26-2007, 09:07 PM

Quote:

Originally Posted by siral3x

Is the modulator the white piece on the IP?

The modulator is on the side of the transmission and regulates the speed of the shifts. The VCV is on the IP and regulates the vacuum level to the modulator.

nothernubie · #**360** 12-26-2007, 11:17 PM

Can someone define "flare" for me - I think that's one of things my tranny's doing. It kicks - really, really bad when cold - from 1st to second and the remaining shifts always seem like it's saying... "I'm shifting now, really, I am shifting now, honest, see I'm shifting" before it finally does a soft slide into gear. Does that have a name?