replacing vacuum element on center vent - PeachParts Mercedes-Benz Forum

erubin · #1 03-28-2003, 07:57 PM

The center vent vacuum element on my 82 300D Turbo leaks. For now I have it plugged off. How do I change it without having to pull the whole dash out? Can it be rebuilt in place?

If you're sure there is no other way to replace it can someone give me an idea of the difficulty (amount of time) and any tricks or headsup doing it via dash removal. Also any parts I should check/change "while I'm there anyway"

Thanks,
Elliot

gsxr · #2 03-28-2003, 10:01 PM

It is basically impossible to repair the pod without removing the dash. Others have done it by cutting a hole in the dash (!!) and then using a dash cover to hide the hole.

The other option is to use a wire or something to force the pod open so you get cold airflow out the center during the summer, and plug the vacuum line. I have done this job 3 times on a 124 chassis but never on a 123. On the 124, the first time it took me 10-12 hours total (replacing ALL the pods while the dash was out), but by the third time I could do it in 4 hours.

HTH,

kerry · #3 03-29-2003, 11:49 PM

Do a search on center vents and you will find tons of information. Some people have changed them in place. I think it is possible. Go to a junkyard and get one to practice on. Mine is wedged open at the moment but someday I may try to repair it in place.

sublettm · #4 03-29-2003, 11:58 PM

I just tackled this project on one of my cars a few weeks ago. It wasn't difficult, just time consuming. It took me about 8 hours start to finish. The bad part about my project was that the pod I thought was bad, turned out to be good, and I still haven't located my problem. I think it is the switch or wahtever it is that the vacuum line runs through directly behind the ACC control panel. If your pod is bad, go ahead and pull your steering wheel, undo all of hte bolts for the dash, pull the instrument cluster, and replace the part. Don't take the easy way out and cut a whole in your dash. I cringe at the thought of doing that.

Mike

lrg · #5 03-30-2003, 12:44 AM

You can change the center pod on a 123 without removing the dash. It's fussy and helps if you have small hands but it can be done because I did it. You'll need to remove the glovebox and the center vents. The whole procedure is laid out in detail in an earlier thread. You should be able to find it in a search.

erubin · #6 04-06-2003, 02:43 PM

LRG,

Well I'm glad you told me that it is to take the center vac element out without pulling the dash. I did it last night. Took about 1 1/2 hours start to finish as I'm a bit deliberate. The hardest part for me was getting the center vents reinstalled. Glad I had extra clips because i lost two when reattaching the element. It definetely beats taking out the dash!

Elliot
1982 300D turbo

kerry · #7 04-06-2003, 03:15 PM

Can you give us a step by step account. Planning to do mine at some point.

gsxr · #8 04-06-2003, 03:17 PM

Elliot, did you remove the entire pod, which (I think) is held in place by those round little clips that slide over the plastic tits on the pod? Or did you just replace the internal diaphragm? I'm tempted to try this myself. Oh, and what tabs did you drop? Sounds like at item I should order several of, in anticipation of losing a few!

BTW - any tips on how to make crow taste better? Maybe salt & pepper...? :p :p

Regards,

lrg · #9 04-07-2003, 12:12 AM

Gsxr, I believe you are 100% correct on the W124, the dash must come out. The 123 has a bit more room. Elliot, I'm guessing you dropped the small round press clips (I think the call them press nuts) that get pushed down on the plastic tabs to hold the pod in place 'cause I dropped a couple too. Gsxr, I had to break the plastic tabs on the old pod to get it out so rebuilding in place is IMHO out of the question. My experience was similar to Elliot's, the hardest part was pushing those #*%#@ press nuts down on the plastic tabs and getting them tight. You'll have your right arm in the glovebox up to the elbow and your left hand jammed in the center vent to hold the pod while your right hand maneuvers some needle nose pliers holding an 1/4" round press nut trying to stick it on the end of a small plastic post while utilizing the Hellen Keller method of alignment. Feels great when you get it done though.

erubin · #10 04-07-2003, 04:50 AM

I did this on a 1982 300D so don't know how it would work on other years or other models. LRG's info was accurate for me so check his model and year.
Removal:
1. Remove glove box. I also removed the glove box light switch which got rid of one of the sharper parts digging into my right forearm.
2. Remove both center vents, this is needed so you can work your left hand into the openings. This is where you must have a hand that is small enough to fit into this opening. My hands happen to be between average and slightly less broad than average for someone who is 5' 10". You will need to remove the rubber duct that attaches to the two center vents. This rubber piece was in fine condition on my car. maybe it will be degraded on other's and need to be replaced although I doubt a slight tear would cause much of an A/C air leak away from the center vents. Reach w/ right arm from the glove box opening and rotate each vent. this disengages the vent locking tabs from the outer (visible from the front of the dash) ring. Pull out the vents from behind the dash (reaching through the glove box), takes a bit of coaxing especially for the left vent. Pull the decorative/locking rings (through the face of the dash) from the center vent openings. Take note of how the large compression washer assembles (hint they slip in from behind the dash).
3. From the glove box opening use needle nose pliers to break off the three vacuum element tits that pass through the steel mounting bracket. You will no longer be able to rebuild these. Hold onto the broken off plastic pieces as you will need the steel press fit locking rings that slip over them to lock in the new element. i recomend that you buy 2-3 spare locking rings cause you're going to break or drop one or two of the old ones. Let me know if you need the part # as I can probably dig it up. You will need a flash light shinning through one of the vent holes during much of this step and the following steps.
4. Remove the black plastic clip/rivet that holds the vac element's linkage arm to the damper. Use a small screw driver or nail to push out (from left to right) the center pin before the clip can be pryed off. Watch you dont drop this clip as you'll need it later. If you dont remove the center pin first you're going to mangle something trying to force the rivet off. Then you'll have to pull the dash or go back to manually proping open the damper. You'll have to get creative on your flash light position in order to see what you're doing.
5. To get the element out you'll need to press in (retract) the elements linkage arm. Now remove the element.
Reassembly:
6. If you have a hand vac pump evacuate the new replacement element. this will cause the arm to retract and facilitates slipping the new element with linkage into place.
7. slip the new element into position. Try to get the locking clips started (by hand) onto the three element tits. It's best to reuse the old ones cause they slip on easy. Use the new ones you bought for backup if you lost or damaged an old one. I used a small socket (8mm?) with extention to finish off pressing on the clips. The socket and extension slip through one of the vent openings.
8. Reattach the plastic rivet that attaches the element linkage to the damper. Reinstal the two vents, locking rings and compression washers. This last sentence represented the most difficulty for me. Put the rubber ducting back onto the vents. Reinstal the vacuum hose to the element.
9. Drink plenty of wine or beer for the next 5 hours you would normally take removing the dash. Wait two weeks for the knuckle damage to heal. you're done!

Thanks LRG, for saying that it can be done.

Note: I replaced the spongy hose (disentegrates in your hands) that goes between the dash mounted temp sensor and venturi/blower with a ~6" scrap piece of ~1 1/4" ID hose. the sizes are from memory and were not actually measured.

gsxr · #11 11-29-2003, 05:47 PM

Hi all, I just did this two days ago, and thought I'd post what I sent to the MBZ email lists. I think this method is easier than dinking with those annoying metal clips, but at any rate, I didn't have to pull the dash so I'm happy!

====================

There were two different methods posted in the past for how to replace that pesky center vent vacuum pod on a W123, *without* pulling the dash. The first method (from "erubin" at Mercedesshop.com forum) involved removing the center vent eyeballs & changing the whole pod, the second method (from Will Rhyins, on the Ritter list) involved rebuilding the pod in place, leaving the center vents in the car as well. Well I finally tackled the job and ended up using a hybrid of the two methods. I guess you could leave the center vents in there, since Will did that, but it seems a lot easier to work on the pod with them removed. So, consider those steps optional. Here's my edited version, mostly a copy & paste from erubin's & Will's posts, with some tweaks based on my install:

====================

First, have a new pod handy (116-800-11-75) and also three of the little attaching metal clips (000-994-96-45). That will cost about $30 or so from Rusty, plus S&H. You may not need the clips but it's worth having them in-hand, just in case, at $1 ea. The "rebuild" kit - actually just a rubber diaphragm - from George Murphy *does* fit this pod, for $5 plus S&H. HOWEVER! The plastic nipple on the pod cover for the vac hose can snap off, since it can be brittle from heat & age. So if you buy the GM kit, you may still be stuck buying a whole new pod if your old one breaks while you're working on it. I had an extra GM diaphragm and used that. You may need to replace some of the Tecalan (plastic) vacuum tubing as well, if it is brittle - hose will work fine if you don't have any. With that out of the way, and assuming you have the parts in your grubby little hands, here's the procedure:

1. Remove glove box completely. I also removed the glove box light switch which got rid of one of the sharper parts digging into my right forearm.

2. Remove both center vents, this is needed so you can work your left hand
into the openings. This is where you must have a hand that is small enough
to fit into this opening! You will need to remove the rubber duct that attaches to the two center vents. Reach w/ right arm from the glove box
opening and hold each vent from the rear. Then turn the front decorative ring about 45 degrees. This should disengage the ring locking tabs from the vent assembly. Pull the decorative rings out the front, then pull the wavy washer rings (through the face of the dash) from the center vent openings. Take note of how the large compression washer assembles (hint they slip in from behind the dash). Pull out the vents from behind the dash (reaching through the glove box). This takes a bit of coaxing, especially for the left vent. I disconnected the electrical wire from the sensor in the middle of the dash, between the 2 vents, because it was in the way.

3. Reach up & across with your hand & carefully remove the rubber vacuum
hose atop the center vacuum element. You can barely see it but can easily
feel your way. A flashlight stuck in one of the center vent opening helps. The element is attached to a bracket with three round metal press clips. DO NOT REMOVE THIS. If you do, you will have a more difficult job on your hands! Remove only the vacuum hose from the top of the vacuum element.

4. After you've carefully removed the vacuum hose, carefully un-clip the
top of the 2-piece vacuum element from the (attached to the bracket) lower
piece. Look at the new one you purchased, practice, memorize how it snaps
together, do it several times in the dark or without looking before you try
to separate & clip together the halves on the one in your car. It's not as hard as you'd think - tools are not required, I could do it with my fingers, at least on the one in the car.

5. With the top half of the vacuum element removed, you can now take out
the rubber diaphram. Remove it--NOTE THE POSITION IT WAS IN. Watch out for the big spring inside, don't drop that under the dash.

6. Replace the rubber diaphragm with the one from the new element (or the new diaphragm from George), snap the new cover on. This is not as easy as it sounds. The new diaphragm must be seated perfectly on the cover (pink section). It may be helpful to have a MityVac handy and apply light vacuum to "suck" the new diaphragm in place on the cover before pressing it on to the base in the car. It took me a few tries to make it seal properly.

7. Make sure you seat the rubber element properly, and make sure you snap the vacuum element top correctly to the old base and all should be well. I stuck both hands into the center vent holes. It takes a decent amount of finger pressure to fully snap all 4 tabs into place. Keep the new lower half of the vacuum element as a trophy for your efforts.

8. Test with Mity-Vac before buttoning up to ensure you did it right &
that it cured your problem. I did mine at least 2X before I got everything
seated properly. Afterwards, mine would leak vacuum slowly, but it worked fine. I didn't attempt to re-do it with zero leakdown.

9. Reinstall the vacuum hose to the element. Start the car, turn the temp wheel to "MIN", and see if the pod operates & opens the flap. Turn it to "MAX, the flap should close. Repeat a couple times to increase your satisfaction of fixing the stupid thing.

NOW you are ready to button things back up! (Better to test *before* reassembly, no?)

10. Reinstall the two vents, locking rings and compression washers. This
last sentence represented the most difficulty for me. If you removed the electrical wire to the dash temp sensor, put that back too. Put the rubber ducting back onto the vents. I taped the rubber duct on to the left vent which prevented it from becoming dislodged during reassembly. It is a real pain to get both vents in place and the rubber booty back on. Next hassle is getting the decorative trim rings in place. Slip the wavy washer back through the front (don't let it drop!), hold the vent from the rear with your right hand, line up the tabs, and press the front ring on tightly. It should snap into place.

11. Check the foam tube that goes in the pipe to the dash temp sensor. Replace if it's falling apart. Reinstall glove box, light switch (if removed), and all the other assorted stuff you took apart.

12. Drink plenty of wine or beer for the next 5 hours you would normally take removing the dash. Wait two weeks for the knuckle damage to heal. You're done!

====================
Credits:

From "erubin", on Mercedeshop.com forums:
http://www.peachparts.com/shopforum/showthread.php?threadid=60821

And,

Will Rhyins
'87 300TD [130K mi]
... '79 300D, gone but not forgotten

====================

HTH,