OK--- Whats with all these vacuum lines???

After doing some research, poking around and reading posts I wanted someone to tell me:

Whats up with all these vaccum lines?

The Germans must be "great plumbers" to have installed such an eloborate system of vacuum lines!

But my main question, for the Techs is: Why? Why use all this vacuum technology, when electrical, makes more sense?

Why? Install a vacuum system, you KNOW will eventually leak?

Why? Does the whole car seem to be tied into a vacuum line?



1983 MB SD300 Diesel

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KyCol

1983 300SD Turbo-Diesel

It's very obvious, you haven't looked under the hood of a Ford lately.
There is really nothing simpler than vacuum.
You can turn things on/off, full blast, gradually, thermostatically controlled, ported vacuum, manifold vacuum, whatever you like.
You can thank the emissions gods for most of it.

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2007 C 230 Sport.

Why install electical solenoids when you KNOW they will evenutally fail?

The fact of the matter is that vacuum systems to control things like HVAC air doors, emission equipment, and many other control functions throughout the vehicle are cheaper and lighter, and OEs don't build cars to last 15+ year without having to replace parts. In fact, all they really care about is that components last through the warranty period under worst case conditions. Believe me, I was an OEM production engineer early in my career, and they all have similar design and durability standards. Every other OEM has equally complex vacuum control systems as Mercedes.

You're probably not old enough to remember vacuum powered windshield wipers on the underpowered cars from the early post-war period. When you stepped on the thottle to accelerate, they stopped working!!!

Despite their complexity, cars are a lot better than 50 years ago - more complex for sure, but better and will last longer, but take increasing maintenance as they age. Same applies to airplanes, ships,... you name it. It always come down to whether it is cheaper in terms or time, expense, and risk of sudden failure and down time to keep fixing the old crock or sell it and buy a new crock.

Duke

Also there is only so much 12 volts can do.

Yep,

Dan alot you said makes sense, make it last past the warrenty.. period...."cheaper" is better? right?

Now, to get sown to brass tacks though , foremost, I'm no mechanic .... so bear with me, but if I decide I may have a small vac leak with my MB in mind, how in the heck do I find it??? I haven't the foggy-est how the lines run nor where to begin? Nor where to start????

Tnx Dan for the reply..






1983 300SD Diesel

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KyCol

1983 300SD Turbo-Diesel

I remember being told that it had to do with power -- early 12V systems just could not run it all unless you made the charging system to large.

Vac power is quite strong for its size and especially weight and it is very simple -- just think -- in the vent system you do not need any limit switches etc.

My problem with mercedes is in some cases they stuck with it too long -- door locks and especially trunk and gas door.

I think I hear motors in my Jag and BMW ACC systems from time to time. I do hate the Benz ACC Vac systems -- But then again the Benz window motors used to go all the time -- so may be we are really lucky they did not go with any more motors.

You need a Mity Vac and a vacuum diagram. It's not as hard to trouble shoot as you might think. The lines are color coded. Get under the hood and check each system. The likely source for are the doors and the actuators in the heat/ac.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

[QUOTE]Originally posted by KYCOL
[B]

how in the heck do I find it???



You need a vacuum diagram, and a change in attitude.

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2007 C 230 Sport.

Like they said Col., you just need a Mity-Vac. A couple of golf tees to use as plugs will help. Vacumm system splits off to feed several systems (brakes, transmission control, EGR, door locks, A/C). Just figure out which system you think you have a problem in and isolate it from system. Use Mity-vac to apply vacumm to that system and see if it will hold vacumm and then start narrowing down that system till you find the leak. Rubber diaphragms in actuators go bad eventually, but really they do last a long time-probably long than an electrical counterpart would. Plus they are usually cheaper to fix. Plastic lines can wear and leak. Underhood lines become brittle from the heat. If you don't want to spring for the good MB CD manual, the Haynes manual for 123 diesels is pretty good o most things. Even the diagrams in the Performance Products catalog for the 123s are pretty usefull. BTW, EGR diaphragms seem to go bad eventually so be sure to test yours. Just hook the mity vac up to the egr directly and see if it will hold vacumm. If it leaks, you can replace it or some times BBs or small ball bearing balls have been known to mysteriously fall into the rubber hose near the EGR. Just relax and take your time working on it. Vacumm systems are simple and just like water systems except you don't get wet! Good luck and let us know what you find.

Bob, you're a master of subtely!

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95 E320 Cabriolet, 159K

appreciate the info guys,

Its not so much an "attitude problem", as it is a "State of confusion"..

Ive never seen so many vac lines in a car before or maybe never looked, definitely never saw things like windows, locks, trunk and tranny etc. controlled by vac, it just seemed like a big challenge to find any leak, for me.

Tnx again,


1983 300SD DIESEL

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KyCol

1983 300SD Turbo-Diesel

For a real mess of vacumm lines, try a late '80s honda with carb. They basically had a pneumatic computer in that car under the hood.
BTW, now that I think about it, you have a 126 chassis, don't you. That may have a vacumm/presure pump under the back seat. Neat pump that provides vacumm to lock and presure to unlock. Still can use the mity-vac to test things. If a line won't hold a vacumm, then there is a leak. Rest of car's vacumm operated systems run off engine vacumm pump.

Ok...I have a 92 190E 2.6. Where can I find a vacume diagram to start checking some of these systems that I have problems with.

My climate control doesnt change the airflow from the dash to the floor. The A/C works great but the heater doesnt work...is that controlled by vacume?

SKI

Yeah, it's on old trick, but I have seen the gas mileage go straight down the toilet on a lot of vehicles with a non-functioning EGR.
It is, after all, an artificial octane enhancer.

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2007 C 230 Sport.

Here I am kinda overwhelmed by the vacuum issue and you tell me to look under the back seat too?? OMG.....LOL

Tnx BOB

1983 300SD Diesel

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KyCol

1983 300SD Turbo-Diesel