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Discussion Starter #1
I hear my vacuum pump whining in back non stop when I drive my car. Everything seems to work fine except for the locks. If I unlock from the driver's side all locks open. If I unlock from the passenger side all locks come up except for the driver's side.

Thoughts?

Thank you.
 

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I hear my vacuum pump whining in back non stop when I drive my car. Everything seems to work fine except for the locks. If I unlock from the driver's side all locks open. If I unlock from the passenger side all locks come up except for the driver's side.

Thoughts?

Thank you.

Sounds like you may have vacuum leak somewhere, i had he same problem where my vacuum pump would cycle every 8 seconds and it would drive me crazy so i got a vacuum tester to see what the issue was, yours sounds like it may be a line to your door.:mad:


one of my leaks was in the rear trunk/boot lid so i was not able to get the trunk to open with the remote and would get a whistle sound that was steady causing the central locking pump to continuously work... there was a vacuum line that goes right to the lock mechanism, where the sound was coming from and also the line did not hold vacuum when tested.

Now off topic:p
as for me it turned out i had two leaks :eek: i would wonder why the center vent would not blow air sometimes. the other one leak was coming from the ACC Vacuum Valve block that looks something like this


Located:


there was a crack along side at the front where it looks like a steel ball bearing causing it not to hold vacuum, making my center vent to go crazy, it would cut off always when i would press on the gas,
well hope this may be of some help to you and anyone else out there. :thumbsup:
 

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Discussion Starter #3
Thank you so much for your write up/photos, very helpful. Mine sounds like yours, it cycles ever 8-10 seconds of so.

I have tackled a lot of things, but never vacuum leaks.

I did notice today that when I turn my AC off that pump quits whining. So am I safe in assuming that the leak is probably related to the AC in some way?

Thanks again.
 

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From what you are describing, it sounds like a leak in the vent control somewhere. You can check without removing the dash.
Take off the underdash cover on the passenger side. Its 3 small bolts and it will slide right out. From there, look in the middle under the glovebox for a gold screw. Remove that and the vacuum control block will be accessible. Pull it down and remove the cover part with the vacuum tubes connected to it. There is a two prong clip on one end. Pull the prongs apart and the cover will come off. There will be a little resistance, but it should be smooth, meaning you dont need to pull hard.
Once that cover is off, you can check each line with a vacuum tester. I have a mity-vac. You can get one at most auto stores for about $30. I use it for bleeding brakes and clutches.
I have a mapping of hose color to bellows. Just havent typed it in anywhere yet. If I remember correctly each separate line should hold vacuum. Some of the bellows are 2 part with 2 connections.
I do have a video and other pics that I need to post someplace. From those, you can see which color vacuum lines go to which bellows.
 

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I dis forget one thing. The quickest way to tell if you have a leak in the bellows is to "gently" remove the connector from the green line to the vacuum block in the engine compartment (the block mentioned above) I used need nose pliers and got them around the connector and pulled. If you get that line out, you can apply a vacuum to it. That green line supplies all of the vacuum into tbe box under the glovebox.
If there is a leak under the dash, you should not hear the vacuum control running with that green line disconnected.
 

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Wow, well I sincerely hope that is not my issue, although is sure sounds like it may be.
I hope you don't have to remove the whole dash for this problem but i guess c280's are a lot different, i was able to access the Bellows right from the glove box, (depending on your year) and also like another member said you can remove the bottom should under the dash, i did both so i had room and light to see everything. i will go outside and take some photos for you as it only takes a few minutes to take apart =)
Okay here are some photos i just took step by step for you to access that vacuum box and bellows its really simple...
hope this helps!

Step one remove 3 phillip screws that hold bottom cover pull down gently from right side or remove your choice.


step two open glove box and remove 4 phillip screws two of the bottom screws are covered with rubber tabs, then pull out glove box gently dont forget to disconnect glove box light to fully remove box


Step three to remove the vent tube follow arrow diagram, first push vent to passenger side gently --> then second pull out vent to driver side <--


Step four Remove vent tube from bottom


Step five! now you have exposed both the vacuum line Box (In Yellow circle)
And the Bellows (In Red Circle) bellows usually slide right out from the side but be careful when releasing the tab on top of the bellows to replace them, you do not want to loose the arm they are connected to because they are under spring tension. It's not a fun task fishing for them. Well good luck and hope this may be of some help to anyone. these pictures were taken on my 1996 C220




NOTE: on some models there is a Bar behind the glove box preventing access from above, so some of you may have to do the work all from the bottom access cover.
 

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C280 is the same as described. With the lower passenger side panel and glovebox removed it is possible to get to two of the bellows. Mine turned out to be on the drivers side which is completely inaccessible without removing the dash. There are a total of 6 bellows. 4 simple and 2 two which adds up to the 8 lines at the control block. The defrost control, fresh/recirculate and drivers side need the dash removed to get to.
If you can get to the control block circled in yellow above, you can get the cover off and check each vacuum line to figure out which bellows is leaking.
 

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Discussion Starter #12
Wow terrific info, thank you. I have actually removed that panel before. I'll start taking a look this weekend. Guess I need to go buy a vac tester next.
 

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Discussion Starter #13 (Edited)
Oh yeah and here is a picture i took where my leak was on my vacuum block be sure to check yours also
Finally had a chance to check mine and guess what? Looks like the same leak!





I'll be checking under the glove box tomorrow, but it surely looks like I need this part at least.

Do you happen to know the part number?
 

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Have the same vacuum block problem

Finally had a chance to check mine and guess what? Looks like the same leak!

I'll be checking under the glove box tomorrow, but it surely looks like I need this part at least.

Do you happen to know the part number?
Guys, thanks - I've been experiencing intermittent operation of the center vent, and my vacuum pump has been cycling periodically when the climate control is on.

5 years since you posted, but you helped me find the exact same problem!

Going to try to remove the block to check the feasibility of repair with J-B Weld. If not, looks like I'll have to order one. So glad I found this before the New Hampshire cold weather gets here.

You guys are awesome!! :)
 
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