Andrew:
You need to study up on the vacuum system generally. There are a few separate pieces to the system (different between 123 and 126) models. If you can figure out which PART of your system is causing your problems, you will fix it more easily.
Nate is right that once any of the small bits start to age out, you'll want to replace all of them. But that only addresses the small bits, and not the valves and longer hoses.
Your car has a vacuum pump that operates:
1) Power brakes;
2) Engine shut-off and transmission modulation;
3) HVAC system;
4) Door Locks (in the 126, the door locks are run by a separate pump).
The vacuum system is color coded, although I don't remember the colors (I THINK door locks are yellow pipes).
If your brakes continue to work, that indicates that:
A) The pump is working;
B) The isolators that keep the brake vacuum protected from vacuum leaks in other sections are working.
So no you need to determine which of the other sections has a leak. YES, this is going to come down to indentifying a leak in the vacuum system.
If you isolate the HVAC and door lock systems, and the problem goes away, then the leak is NOT in the engine shut-off / transmission modulation piping. On the other hand, if you isolate the HVAC and door lock systems, and the problem remains, however intermittently, then you have shown that there is one or more leaks in the engine management piping.
You need to carefully isolate (disconnect) systems until you find which one is the source of the leak (vacuum drain). Then you have many fewer pipes to search through, since each system has its own piping.
The door locks, with their mechanical bladders actuated by vacuum, have constant usage and thus high probabilities of wear and failure. So they are the first to be isolated.
The HVAC is generally more 'necessary' for user comfort than door locks, but unnecessary for actual vehicle operation. So it is the next system to check.
You can isolate the systems in the engine compartment, where the pipes break off from the main vacuum line. Golf T's can be used to plug the line when you disconnect.
Tom
In a message dated 6/23/2013 4:36:25 P.M. Pacific Daylight Time, okldboy@yahoo.com writes:
Thanks, Nate.
The odd bit is that the problem is intermittent. Today the car ran fine including locks, acc, shut off, etc. I am going to replace all the vacuum rubber connectors but wonder if it is not something else - hard to understand why shutting off the climate control would lead to everything working, including the climate control itself when I turned it back on today.
Andrew
Sent from Yahoo! Mail for iPhone |
From: Nate <vwnate1@yahoo.com>;
To: <diesel_mercedes@yahoogroups.com>;
Subject: [diesel_mercedes] Re: Vacuum leaks - 123
Sent: Sun, Jun 23, 2013 7:10:26 PM
Andrew ;
Your comment " tightened up the ignition switch connections " is very telling ~ you _cannot_ tighten up a vacuum leak ~ you *MUST* replace the short bit of rubber hose that was loose .
Then , carefully and methodically go around the entire car and replace every single short hose bit you can find as they get old and don't seal properly , the *only* cure is to rep[lace them all , this takes far more vacuum hose than you think so buy 10' at least .
Then begin replacing all those rubber 'Y' connectors .
Then and not before , can you consider anything else .
-Nate
Andrew wrote :
>
> Hi all
> Apologies if this has been covered. My 82 300D turbo has developed a vacuum leak and I am trying to resolve it. Started to take a second longer to shut off and the locks were slower so I replaced the vacuum shutoff. All went back to normal. Later in the day I changed the oil and filter and it started doing the same thing, so I checked all the connectors around the filter housing. No improvement. Pulled the under dash panel and tightened the ignition switch connections and then all seemed resolved. Now, several weeks later, it is acting up again - slow shut off, locks barely working, reduced flow from dash vents. Brakes and shifting are fine. Odd thing is, last night While driving i turned off the climate control and a few secs later the door locks started working and the engine shut off just fine. I will grab my vacuum tester and start checking the system but the question is whether the shutting off of the acc leads to any clue re the source of the leak. Any thoughts will be appreciated.
>
> Andrew
> 71 250C 62k
> 82 300D 166k
>
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