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Discussion Starter · #1 ·
Well, I looked over the dieselgiant page for help regarding my issues with vacuum. Luckily i have 2 123's, so i can compare results.

My '82 seems to keep a strong vacuum ovrenight (the locks); however, I went to test each of the lines going through the firewall and i noticed soemthing.. well.. funny.

Everything held an "okay" vacuum (much better than my '81, that is), except for the black hose. In fact it seemed to be loose.. I pulled it straight out of the firewall becasue it wasn't connected on the other end at all. It goes back about maybe 24-30 inches under the driver's side dashboard and then there's nothing.

Is it normally a junction or is it black straight back to the vacuum reservoir? (as i understand it, the black one is supposed to go to the vacuum reservoir).

Also, I found some connectors and hoses which need replacing. Can i just use some kragen hose or do i have to search out the finest german hose available? I'm asking for opinion here. Also, the same goes for 3 and 4 way connectors: should I find some original german made rubber or can i find generic kragen parts here? In either event, where should i go to get these if not kragen (and i know we all love kragen).

Thanks for any help!

My '81 has leaks all over- won't hold anything.. i have no clue where to start besides just replacing everything.
 

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Not sure about the black hose. Do you have a gasser? If it's a 3rd Series, it should have that economy gauge, which is connected directly to a crossing in the enginedepartment without a valve, but that hose is light grey. If its a Euro version, it could be the connection for the heights adjustment of the headlights - but the hoses are supposed be be purple. There is no direct line to the reservoir, I think it's just connected somewhere to the central locking in the back.

You can take the hoses and connectors you like, but they are not very expensive at Mercedes.

A hint about the vacuum elements: if you have the late version (the black ones), there's a good chance, that thap cap on top is stuck. There's a Bosch-part, which fits perfectly. The Number is: BO 3 340 522 025, looks like this:

 

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Discussion Starter · #4 ·
really? That's odd. well.. it makes sense though, seeing that my '82 isn't showing any vacuum problems.
 

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Discussion Starter · #5 · (Edited)
Ok so I did a complete once-over on my vacuum system on my '81 non turbo manual transmission. Its about as simple as a lawn mower..

anyways I found major leaks in odd places- like the vacuum "junction" connector on top of the engine valve cover. I used epoxy to fix it.. It could be prettier but it works great. Also broke off one of the ports on the thermo vacuum switch.

How exactly does that switch work, what does it do, and what's the "end result" difference in the california and non-california switches?

I epoxy'ed that thing back on too. it seems to be holding just fine. As I had assumed, the door locks are a huge leak. I capped off the junction to the door lock tubes.

One thing that I didn't figure out was the HVAC system tube: i used my vacuum pump and it seems to hold a vacuum; however, when i tested the system by connecting the vacuum gague, REPLACING the hvac, the system reads like 20 (ft hg?). When I use the vacuum gague to replace any other system on that 4-way junction, the system reads 5 (ft Hg). Also, the car won't shut off properly when the HVAC is connected, but when blocked off, it does.. so something is obviously wrong with the HVAC-- but why would it hold a vacuum?

Finally, my '82 has that black hose previously discussed -- open, vented under dash. My '81 has the black hose under the dash, but it has a metal pellet blocking it off. I'm not sure which is the proper setup. I assume that it is the former. Should I remove it?

EDIT: i thought for a minute and figured out why the HVAC would act different when the car is off and on. Answer: because i had the heater on at the time (duh). anyways i need to do more by way of testing the HVAC. i really don't want to. I live in a temperate climate- dont' need it.
 

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1980 300D
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vac problems

check out the fittings and integrity of the dreaded heater servo. Lots of opportunity to lose vacuum internally and in the myriad of connections...
 

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1992 300D, 1999 E320 turbodiesel
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As a 300TD newbie, the vacuum hoses are a mystery to me. Kind of reminds me of the hydraulic systems in the Citroens. Sometimes electricity is a better solution.

Anyway, in changing the oil, I did unplug some hoses (despite being forewarned). Now, despite getting the hoses back as best I could, the car won't turn off without the engine kill switch being pushed. Is there resource that I can SEE that will tell me where the various hoses near the oil filter should go? Just a simple picture would be great.

Thanks for your help.
 
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