dang! vacuum problem-a/c related, help needed!

[RG5384]

Well i get to troubleshoot yet another pesky vacuum problem. This time related to my a/c system. The defrost vent simply will not shut off. I have turned the system to max blower and min temp, and it still stays on the defrost vent. Sure, some air comes out the normal a/c vents, but not near as much as came out yesterday or earlier today. Also, the car wont shut off quite as quick anymore eiather, it kind of dies out instead of instantly shutting off like it used to. The brakes seem fine however, so my leak can't possibly be all that bad. Any ideas on where to start? the car is a 1983 300SD
thanks
Ryan

[michael rybikowsky]

You have a vacum leak somewhere.To me this is the biggest pain in the arse,to service on these cars.Start under the hood,look at every connection on the vac lines.Feel under them,if you are lucky as I recently was you will find a split coupling.If not it is up under the dash with a miti vac.Good luck Michael Carpe diem

[engatwork]

I would bet that the problem is under the dash. To prove it disconnect the vacuum line going to the air conditioning system and plug the line on the vacuum pump side. This will pretty much take the a/c vacuum system out of the picture. Run the car and if it shuts off ok then the problem is under the dash in the form of a leak. The only way to pinpoint it then is to go through each element and see which one does not hold a vacuum. You probably have a leaking vacuum element.

[RG5384]

thanks, but i have no idea where any of these parts are located. I can only see one pink cylinder thing with the drivers side footwell removed. Where is the rest of the stuff? please don't tell me i have to take the dash off......
thanks
Ryan

[engatwork]

you don't have to take the dash off. Look to the right of the brake booster. You should see the vacuum lines and where they split off and go into the dash. One of those supplies vacuum to the a/c components. That is the one that you want to start homing in on. That pink thing is a vacuum element. Now you have to find which one is leaking. If you pull the glove box out you should see at least one more behind it. Remove the kick panels under the dash and the glove box and start testing them.

[RG5384]

ok thanks, do i really need a miti-vac or can i just get some extra tubing and suck into it, and if it holds it then i'm fine? thanks
Ryan

[psfred]

Ryan:

Start in the engine compartment -- the vacuum systems for shutoff and A/C and locks are separate. If both are working funny, I'd suspect either a leaking line (where they both attach or at the booster) or a dead vaccuum pump.

If the diaphram in the vacuum pump is gone, you will be burning oil big time, as in a huge blue cloud out the back and a droning noise from the engine. The check valves can go bad, too.

On the big hose going to the brake booster there will be one or two (or three?) hard plastic lines attached. One should be brown with a blue stripe -- this goes to the ignition switch. The other will be green or blue (or both, I'm not too familiar with this model). One will run the locks, the other the A/C, usually. Check the rubber sleeves at the ends of the lines -- the hard plastic should be OK. The rubber goes bad, and the lines leak. You don't use all that much vacuum for the brakes.

The plastic T in the line can go bad, too.

Further up toward the passenger compartment there will be a couple blue plastic check valves in the line -- these can crack, and leak.

There are also several vacuum reserviors that look like a bunch of plastic balls stuck together, but I'm pretty sure they aren't your problem.

The vacuum lines are pretty easy to identify once you find them -- check all the connections and I'm sure you will find the problem is a rubber connector. They can be replaced with vacuum line of the appropriate size from the autoparts store.

To check the vacuum pump, pull a line off and check that there is strong vacuum in the main line. If you can't find any leaks and there is little or no vaccum in the line, the pump is bad.

You can check for leaks by sucking on a hose, but a mitivac or equivalent hand vacuum pump is MUCH easier -- some of the vacuum reservoirs are pretty large!

Peter

[RG5384]

ok thanks guys, i'll probably work on it a lil tonight

[RG5384]

well i *temporarily* solved my problem my simply insterting the a/c line into the rubber sleeve with a TON of force. All of the rubber connections seem to be cracking etc, so i think this weekend they will ALL be replaced(or at least the easy acces ones). Afterall, she's 18 years old, so she deserves it!
thanks again
Ryan

[psfred]

Ryan:

Most probably, only the rubber parts in the engine compartment are bad -- most of the rubber connectors on my '72 220D in the interior are still fine!

Peter