1987 190D Turbo vacuum help needed - PeachParts Mercedes-Benz Forum

Turbo190D · #1 09-13-2018, 02:27 PM

Hey guys, I've got a copy of the service manual but I can't seem to find anything about the transmission or vacuum system in it. I took the car to a transmission shop to have the automatic trans rebuilt (it was a mess, but he got it all fixed) but he says now there's no vacuum at the modulator. Without a diagram of how the system works I'm a bit lost as to what is supposed to do what. Is there a diagram for the vacuum system somewhere, or a common part that would fail? The door locks still work and the engine turns off, so something is getting vacuum.

Turbo190D · #2 09-13-2018, 03:18 PM

The guy at the transmission shop is a pretty nice guy, he said that he just decided he'd see if he could figure out what's going on. He checked vacuum at spots between the modulator and the pump until he got all the way back to the pump. He said there's no vacuum there at all. So now the question changes to: Is it possible to repair the vacuum pump, or do I just have to buy a new one?

Clemson88 · #3 09-13-2018, 03:27 PM

This is all I have. I don't know your car but perhaps there's a diagram on the link.

Vacuum Diagrams

Do yourself a favor and learn to search. Many of the senior and more knowledgeable gentlemen here depend on you to help newbies find solutions. You won't be able to help if you can't navigate the paths provided. We all try to give back when we can and I'm glad to help even though at times I may be no help at all.

shertex · #4 09-13-2018, 03:28 PM

I don’t understand… If the vacuum actuated shut off valve is working aren’t you getting vacuum?

Turbo190D · #5 09-13-2018, 03:49 PM

Quote:

Originally Posted by shertex

I don’t understand… If the vacuum actuated shut off valve is working aren’t you getting vacuum?

That's why I'm confused. The shut off has always worked, but I have had problems with no vacuum at things like the heater core water-switch thing (I can't remember what it's called at the moment).

As for searching all I've been able to find is stuff for the 190E and then things like the 300. I use forums regularly so I know how to search. I get that there are people that don't, but I wouldn't post here if I could have found the information myself.

When I pick the car up later I'll see if I can do some testing myself, unfortunately work my work schedule it's likely it'll just be sitting for a while until I have time to fiddle with it.

Even if I do need to swap the pump I would like to have a diagram (why this isn't in the service manual boggles my mind) to assist in tracking down leaks that I'm sure are going to be present.

Mxfrank · #6 09-13-2018, 05:44 PM

I'm only going to leave this up for 24 hours. Download it and keep it somewhere safe:

https://www.coolcatcorp.com/190Restoration/190dservice.pdf

Mxfrank · #7 09-13-2018, 05:48 PM

Before I leave the thread:

The vacuum modulator is connected to the blue vacuum amplifier on the left side of the firewall. The other connections on the amplifier are a vacuum source, a feed to the VCV on the side of the injection pump, and a feed from the boost port on the side of the manifold. Check for a loose connection, especially on the VCV where it's tough to see. The shutoff and the brakes will usually work, even if there are large vacuum leaks elsewhere in the system. That part of the system is fed by a different port on the pump.

Finally, the vacuum leak can be anywhere under the hood. What you want to do is start at the small vacuum port on the pump, and move forward through each branch checking for vacuum.

Diesel911 · #8 09-13-2018, 10:29 PM

If your Vacuum Pump was not working your Power Brakes would also not be working. You would have extremely hard braking.

If the local auto parts store has the free tool rentals you can barrow a vacuum gauge and check for your self.

You always wonder of the Kind Mechanic is actually going to hose you on something else. Better to check what you can yourself.

A friend of mine was told She needed a rebuilt transmission. Once She told them she no Money they lost interest. 5 years later the Transmission was still good but the Car got totaled in an accident.

Turbo190D · #9 09-14-2018, 10:02 AM

Frank, seriously, you are my favorite. Seems like every time I have question you have some life saving advice.

After I got the car home last night from the trans shop (HOLY CRAP what a difference - drives like a dream compared to how it used to) I did a bit of testing. The vacuum pump itself is fine, the thing that he was referring to as the pump I'm pretty sure was actually the shutoff valve. Now that I have this flipping excellent diagram, I'm going to print it off and go through every one of these hoses/connections, highlight them as I verify that they're good.

Thanks again!

vstech · #10 09-15-2018, 05:09 PM

Quote:

Originally Posted by Mxfrank

I'm only going to leave this up for 24 hours. Download it and keep it somewhere safe:

https://www.coolcatcorp.com/190Restoration/190dservice.pdf

Ugh... missed it.

Mxfrank · #11 09-15-2018, 06:19 PM

I've made a large collection of 201 info available for download. It'll only be up for a couple of days, I can't spare the disk space or bandwidth. So take what you need and store it somewhere safe:

https://www.coolcatcorp.com/190Restoration/Download

Dr. Sternschnuppe · #12 09-16-2018, 07:36 AM

Quote:

Originally Posted by Turbo190D

Without a diagram of how the system works I'm a bit lost as to what is supposed to do what. Is there a diagram for the vacuum system somewhere, or a common part that would fail?

See attached pdf file.

Turbo190D · #13 09-17-2018, 09:19 AM

Quote:

Originally Posted by Dr. Sternschnuppe

See attached pdf file.

Oh nice, the image quality on that one is excellent!

So far I know there is a vacuum leak in the EGR system, which I'm planning to just remove completely.

Turbo190D · #14 10-03-2018, 11:34 AM

For anyone else searching for this later, here is the english translation of Dr. S's document:
Fig 07 1/6 Vacuum Line Layout
1. Injection pump
2. Governor
6. Vacuum shut off unit
9. Vacuum reservoir on left front wheel housing behind plastic ???
60 EGR valve
61a Orifice
61b Orifice
62 Filter
62a Filter
65 Vacuum control valve
67 Vacuum pump
72 Vacuum damper
103 Aneroid compensator (ALDA)
123 Vacuum amplifier
137 Turbocharger
138 Intake manifold
140 Brake booster check valve
Y22 Electro-magnetic actuator (idle speed)
Y29 Vacuum amplifier switch-over valve automatic transmission
Y30 Engine overload protection switch-over valve
Y31/1 EGR valve vacuum transducer

a vent line to passenger compartment
b key engine stop
c other consumers
d vacuum modulator valve automatic transmission
e brake booster

Connections on vacuum amplifier and vacuum transducer

PRE Boost pressure from aneroid compensator (ALDA)
TRA To vacuum modulator valve, automatic transmission
VAC Vacuum from vacuum pump
VCV To vacuum control valve
ATM Vent line to passenger compartment
OUT To EGR valve

sw – black
bl – blue
br – brown
gr – grey
vi – purple
rt – red
ws - white

Turbo190D · #15 10-03-2018, 11:39 AM

Also, I finally got around to getting a vacuum testing kit and tested my vacuum pump last night. It's working fine and I confirmed there are no leaks on the brake booster side. The EGR side of things is all disconnected, so I've started replacing bits of rubber hose in the other parts of the vacuum system.

On the lines marked a or "vent line to passenger compartment", an air tight seal is not required here, as it's just a vent and not an actual vacuum, correct?