Dash Removal Guide, Center Air Vent Solution, How to find Vacuum Leak, 148 pics

[zadefaraj]

With this post, I will detail how I found my vacuum leak, and how I removed my dashboard and all the components to access and correct it. Please read it in full, and note that this is only for reference and may possibly contain errors, missing steps, and, or information specific to my 1995 C280. In other words, I don’t want to be held responsible.

http://www.corpfr.com/c280/Dashboard.htm

It's about 13 pages of text, and over 140 pictures, and way too large to fit on one forum. Took me a while to write up so I hope this helps someone.


Zade Faraj

[renerodz]

Hey,

Thanks much! I have the problem too.

Rene

[alphanumeric]

I might have this same problem.. when any AIR is blowing through my system.. I cant select which vent the air comes out of.. it comes out of every vent no matter what I select on the climat control knob.

I thought it was from installing my own head unit... and hopefully wont require the whole dashboard to be removed...

[zadefaraj]

Before removing the dash, I would have a good look at
1. the vacuum distributor block in the engine compartment, and
2. vacuum test all the lines on the vacuum control unit attatched to the fan motor box, behind the glovebox. The pics and info should guide you there


Zade

[zadefaraj]

Btw, you can also vacuum test all the lines on the vacuum distributor block in the engine compartment. The only one I know that leads to the vents is the green one, but I'm not sure if it will give you any info if it does or does not hold pressure. The only way to accurately tell if any of the lines in your vent system aren't holding vacuum is to test them individually.

Zade

[htfan1]

Thank you very much zadefaraj!

We appreciate you sharing all of your hard earned information.

I'm just another member of the "annoying vacuum pump noise and busted center vent" club.

[zadefaraj]

No problem! I hope everyone finds the info useful. Beleive me, those center vents are a life saver now that summer has started in Texas. You know, if you test the vacuum lines behind the dash, and find out that the one affected is number 106, then you shouldn't have to remove the dash.

http://www.corpfr.com/c280/CIMG1722.JPG

I replaced number 104 and number 32, where 104 was the one that controlled the center vents. You might be able to reach it without removing the dash via the guage cluster cavity, but im not 100% sure.

Good luck and i'm here if anyone needs more info.

[Abuimad]

i got the same problem, thanks a loot for that post

[nick_nolastname]

Whoever you are, I want to offer you my sincere thanks for going through all the trouble to document that.

Volunteer tech support in forums is often taken advantage of without so much as even a thank you. I wanted to make sure this time is different. Your work will be a help to countless people across the world because it seems most of these cars are afflicted with this same problem.

I've downloaded your instructions and pictures, and it helped me find the problem with my wife's car. Im on the way down to MB in a few minutes to get the part. Your instrument cluster and radio removal instructions will help me replace the burnt out bulbs as well.

Do you have a Pay Pal account? I'll buy you a couple of beers.

Thanks buddy. Thank YOU!

[zadefaraj]

Thanks so much for taking the time to be so kind, you are more than welcome. I hope you didn't run into any problems, and if you do, please feel free to drop me a line at zadeatuh@hotmail.com

Btw, Thanks for the drink offer, and if you ever happen to make it down to Houston, maybe i'll take you up on that.

Take care and let me know how it turns out; Are you fixing a vacuum leak?

[sultanC36]

thank you zadefaraj

for the write up it is a huge help

[nick_nolastname]

The vacuum distribution block under the hood was cracked, causing the high rev shift from second when cold as I read about, and also the center vent cycling on and off when you accelerate and let off the gas thereby changing the engine vacuum. I replaced it for $24 or something close to it. It cracked at the little ball bearing just like everyone elses.

The right center vent bellows was leaking, so I plugged it up.

That passed the remaining vacuum to the left one, which works.

I will accept 1/2 a center vent rather than pull the dash out.

The only remaining problem is the recirc vent, if activated, will cause the trunk vacuum pump to cycle. I told the wife to just not use that, she never does anyway.

The trunk pump will also cycle if she puts the temp setting on LO instead of a number, or if the climate control is turned off entirely. I am guessing that this is due to the recirc closing for maximum cooling or just sealing the car up with the climate control is off.

All in all, what a quirky and stupid idea, must have been all that strong German beer they drink over there.

I would not consider the purchase of another Mercedes after owning this one. They have lost me as a customer for life. But the wife loves it so I am stuck with it as my German kit car for a while at least. You wouldnt believe all the other things that have gone wrong with this car.... or maybe you would. If I hadnt done almost all the work myself we would probably be out another 4-5K for repairs.

To reciprocate in sharing knowledge, I've replaced the water pump. If you need a little coaching with that send me a PM through this forum so I will get an email about it. I dont check this forum except when her car breaks. ( so about once a month from now on LOL ) I've replaced a lot of other crap too but based on your online guide you wont need any assistance with those things, you have the skills to figure it out yourself. The water pump can be a little tricky, but once you see how its done it's almost elegant the way it goes together.


Good luck to all.

[1998K]

Dear Nick,

I really thank you for all your contribution on our forum.

thanks

Marco

[htfan1]

Originally posted by nick_nolastname


The right center vent bellows was leaking, so I plugged it up.

That passed the remaining vacuum to the left one, which works.

I will accept 1/2 a center vent rather than pull the dash out.

I have some questions and would appreciate the help.

1) Were you able to get to both center vent bellows without pulling off the dash? If so, how did you access them?

2) What were the ref. numbers for the center vent bellows on the diagram provided by zadefaraj?

Diagram: http://www.corpfr.com/c280/CIMG1722.JPG

I'm ready to dive in, would just like a better idea of where...

[zadefaraj]

htfan1,

The center vent bellow that I replaced was Ref. No. 104. It is to the left of the center vents and COULD possibly be reached with the gauge cluster out of the way or from below the foot well. I'm not sure if its entirely possible because I haven't checked, but if you are in the process of taking out the dashboard, try checking it out. Actually, from what I recall, it might be possible to reach it from the drivers side footwell, but its an awful tight squeeze. I'll have a look tomorrow and let you know if it can be done.

Take care, good luck, and let me know if you need any more help.



zade

[htfan1]

Originally posted by zadefaraj !!
htfan1,

The center vent bellow that I replaced was Ref. No. 104. It is to the left of the center vents and COULD possibly be reached with the gauge cluster out of the way or from below the foot well. I'm not sure if its entirely possible because I haven't checked, but if you are in the process of taking out the dashboard, try checking it out. Actually, from what I recall, it might be possible to reach it from the drivers side footwell, but its an awful tight squeeze. I'll have a look tomorrow and let you know if it can be done.

Take care, good luck, and let me know if you need any more help.



zade

Thank you again zadefaraj

I've spent the last hour listening for leaks in my dash.

There is a loud hissing noise coming from what I beleive is a bellow directly behind the center of the passenger side mini-glove compartment. I've removed the bottom cover panel on the passenger side and the glove compartment velvet insert.

Could this be it?!?!!? The hissing noise seems to match the vacuum pump pulses. When I place my hand next to it I can feel a subtle pulse of air.

I may be able to get to it without removing the dash. I can't really tell which number it is on the diagram you provided (could be #352).

What do you think? Could this bellow (?) be causing my center vent issue?

[zadefaraj]

I replaced my number 352 and that was the hardest one to reach. Its a pain and most likely requires you remove the entire dash. I was not able to reach it without removing it, and even with it out, I still hard a hard time getting a finger on it. The loud hissing noise you may hear could be coming from that vacuum diaphragm block in the engine compartment. The best way to test for a leak is to purchase a small vacuum pump from your local auto parts store and test the lines shown in the pics. Thats a sure fire way to figure out which line is leaking, and trace it to the source. Listening for the leak didnt help me very much. It was so hard to hear with all the things going on in the car, its almost impossible. I'm also not sure why you would feel a pulse of air, if anything, it should lightly cause suction on your finger. Provide more info and details and I will be glad to help. I've got to rest now though, got exams.. ughh.

zade

[zadefaraj]

Just wanted to add that number 352 is behind the passenger airbag, just behind the start of the windshield against the firewall. Its very deep, and if i recall correctly, virtually impossible to reach without removing the dash. keep me posted!

[htfan1]

Originally posted by zadefaraj
Just wanted to add that number 352 is behind the passenger airbag, just behind the start of the windshield against the firewall. Its very deep, and if i recall correctly, virtually impossible to reach without removing the dash. keep me posted!

Yes, the leak noise seems to be coming from 352. Too bad is so hard to reach. I'll stop and get a vacuum tester to narrow down the actual problem.

For now, I've disconnected the green power connector from the vent control block. This has STOPPED the vacuum leak "and the pump "whrring" noise", but I can no longer control my vents. The air comes out to top and sides only (still better than WHRRING).

I'll try running this way temporarily, because it's wonderful driving without the dreaded vacuum pump noise!

[htfan1]

Does anyone have a list of the connections between bellow number on the diagram http://www.corpfr.com/c280/CIMG1722.JPG and the #'s on the vacuum/vent control block http://www.corpfr.com/c280/P1010184.jpg ?

For example, bellow number 104 connects to #6 on the vacuum/vent control block. (just an example, I don't know which one it really is.)

[nick_nolastname]

Originally posted by htfan1
I have some questions and would appreciate the help.

1) Were you able to get to both center vent bellows without pulling off the dash? If so, how did you access them?

2) What were the ref. numbers for the center vent bellows on the diagram provided by zadefaraj?

Diagram: http://www.corpfr.com/c280/CIMG1722.JPG

I'm ready to dive in, would just like a better idea of where...

What I meant by "plugging them up" is from the passenger side lower panel access to the dash I took those individual lines going to the bellows and sealed them. Apparently the two center dash vents share vacuun, so if one leaks the other will fail to function. I blocked off the faulty one with silicon sealer, leaving the other operational. Keep in mind I am strictly a DIY'er so you can take anything I say for what its worth. Good luck.

[zadefaraj]

By disconnecting the power to that distribution block, you have pretty much stopped the vacuum from being redistributed when you change vent positions. I'm quite suprised you are actually able to physcially hear the leak because as I said before, mine was so small, it was undetectable.

Also, I'm sorry, I dont have a diagram that shows where all those lines go. I was going to make one, but I'm not sure what happened. I think the vacuum pump will be very helpful in determining which bellow is afflicted, and could save you from potentially having to remove the dash. If it is number 352, then I'm afraid their is little hope.

If you ask me, I think the repair was worth the time and money. I spent a lot less than paying at a dealer, I learned a lot more about my car, and the A/C works absolutely perfect. Now i just wish the the rest of the car was the same.

I think one of the main reasons these fail is because of their location and prolonged sensitivity to heat and other such extreme conditions. These days, I try to always park my car indoors or under some sort of shade; protecting my dash and all the delicate items behind it.

If you do decide to take out the dash, theirs a lot of stuff to keep together, so organization is the key. Also, try and replace and small cushions that may be in place because they help prevent creaking when you drive over unstable roads.

Feel free to ask more questions!


Zade

[zadefaraj]

you could also try checking with the dealer to see if they know which bellow each line connects to. Worth a try

[htfan1]

Originally posted by zadefaraj
you could also try checking with the dealer to see if they know which bellow each line connects to. Worth a try

Thank you! I appreciate your input.

As I go through this, I'll document what I find and add to the knowledgebase here.

One more small question: What is the proper way to remove the vacuum connections from the vacuum/vent control module?

Do you have to remove the entire top with all line attached? Or just pull out each one...

[zadefaraj]

You have to pull the entire line assembly off. You might want to draw out which one goes where (color with hole number) because it will get confusing if you dont have the factory diagram. The pics show how to release the locking mechanism:

http://www.corpfr.com/c280/P1010185.jpg
http://www.corpfr.com/c280/P1010188.jpg
http://www.corpfr.com/c280/P1010189.jpg


It almost feels like you are peeling it off from one side to the other. Its quite flexibile if you ask me, but be on the safe side.
Once you have them out like in this last pic, you can simply push them upwards and pop them out to test each line individually if you'd like. Keep in mind: the far right one should be the one that supplies the vaccum. Test them all and let me know what happens.

http://www.corpfr.com/c280/P1010193.jpg

zade