Hi,

My 94 c280 is acting up with noise from somewhere around the passenger side rear/trunk area. The problem started this a.m. (Don' t know if if relates to the drop in temperature today in Toronto). Now everytime I lock the doors, I can hear a loud noise from that area, despite normal functioning of doors and trunk/gas cap compartment locks.

I am wondering if my door lock system is beginning to show a vacuum leak. Am I looking at big $$ for repair?

Any advice on what I should check will be much appreciated.

KC

 

was it a vacuum leak or the fuel pump noise?

 

Hi Sleepwalker,

The noise sounds like some metal hitting onto another rigid structure only when I lock the doors (perhaps a rubber seal or something like that came loose?). As far as I can tell, the locks are still working this morning.

But then the car developed a second problem which I had before.......this morning I couldn't start the car. It will crank but no pick up. I kept the key turned until it finally started. Once the car is warm, I don't seem to have problem re-starting it up again. The same problem happened about 2 years ago (only on cold start) and I have since had a new battery, new fuel pump (then the problem went away), new wires and spark plugs, and it just got a new alternator as well.

I was thinking whether the noise around the lock/vacuum would cause any problem on cold starts but a friend of mine said he had similar problem on his car and it turned out to be water in the fuel pump getting forzen in low temp (here in Toronto).

My mechanic is away for a month so my only alternative solution is to pray.....

Any help is appreciated.

KC

 

Sorry Sleepwalker, just one correction............the car didn't get a new fuel pump but a new fuel filter.....interesting that you asked if it is fuel pump noise.....I have no idea how it sounds.

KC

 

the fuel pump got a continues buzzing noise with a little gurgling sometimes.

if you can only hear the noise while locking or unlocking the door, then it can be the PSE (central locking pump). the noise of this one is high pitched similar to portable drill. it is encased in thick styrofoam to reduce the noise level.

[IMG]local://upfiles/1/117FF9023F97425083E6CA7CFF1B0A87.jpg[/IMG]

[IMG]local://upfiles/1/DDBFFD3ED0394E7CA18A3D951B1F84DE.jpg[/IMG]

 

Thanks Sleepwalker for your picture. They make it a lot easier for me to locate. I am planning to pull out the trunk liner and check to see what went wrong with the locking unit.

In terms of the starting problem, it only happened this am and then throughout the day, it was okay....but who knows what life brings tomorrow morning when I start it.

Your help is very much appreciated.

KC

 

Does MB really make use of some form of pneumatic pump to lock/unlock doors?

Since when has Benz been doing this?

Don't all the normal cars(Detroit and Jap makes) use electric-motor-driven plunger-type mechanism?

Isn't the electric-motor type more reliable and has fewer parts to break down?

 

they have been using it as standard since mid 80's models. earlier than that, it is still vacuum but with intake manifold assist and a reservoir to store the vacuum.

i also don't understand why mb has to use electric>pneumatic>mechanical locking when it can go electric>mechanical directly.

but now it's a bit too late for them to re-design it because it is also use for door closing assist, multi-contour seats, and central locking.

 

Sleepwalker,

I still haven't got the chance to rip the trunk liner open but luckily the car started as usual this am. Of course I have yet to see how it behaves when I leave work today.

Anyway, my search on the forum seems to tell me that if there is a vacuum leak for the door locks, I can also have engine problems or the car may stall, right?

Hard for me to imagine if a door lock fails that one can end up getting stranded.

Thanks again for your help.

KC

 

i cannot agree with that yet.

stalling the car on the road due to vacuum leak is a very dangerous case for MB to consider.

simply there is no link that can make it happen.