R129 door locking vacuum pump

[Chris Taylor]

Hi hop3

I’m afraid I’ve never had issues with the hoses so have not had to re attach hoses to nipples. It sounds like you’re already doing what I would do.
Is the crack in the manifold of the pump? If so I think they can sometimes be repaired. There are videos on YouTube from what I remember.

 

[hop3]

Hi Chris
10/10 for a prompt reply.
No, its the manifold in the engine compartment. Lost Kiwi had a pic which alerted me to the issue.
I haven't touched the pump in the boot, and hopefully won't if the issue is with the manifold. Theres some skill in softening the small bore hoses without heat hardening them, which I don't have and cant seem to find advice on the web -Mr google is usually good at that.
I have a 98 silver SL2800, one of the first with the V6 engine, Grey interior.
best wishes

 

[Chris Taylor]

I’ve a similar one. Mine is a 1998 silver 280 with the straight six and black interior.

I had a crack in the manifold next to the ball bearing but it wasn’t the culprit. It was the pump in the boot with mine.
It would take 20 seconds before the boot lock unlocked.
Everyone assumes it’s down to vacuum leaks as that makes sense but I checked all the lines with a pump. Everything was working so I knew it had to be the pump.
Just noticed the photo of the actuator in the pump hadn’t uploaded so I’ve attached it.


This is the principle of how the actuator operates.
Also a picture of my pump.

 

[hop3]

thanks
I cut the tube where it meets the manifold inlet nipple, as it had folded/creased and blocked airflow/vaccum.
My first task is to get the vacuum lines back on to the nipple on the manifold. In your photos you will see they have to expand 2x the diameter- mine seem to have hardened with age so today might try and get a 3mm flexible sleeve to go over the tube and nipple.
The boot opened on mine- Everything locks but except for the boot, but will not unlock.
Its a good feeling when you find the solution- just takes time...

 

[hop3]

Looks identical but sadly doesn't appear to be a direct swap (later modified part). Must have electronic differences

Good evening lost kiwi.
Ive just picked up this thread on issues with the manifold and pump in a R129 SL.
My immediate issue is the technique to get the white air line back onto the nipple. I have tried boiling water and a hair drier, but if the pipe gets too soft, it collapses. Any advice?
( the white inlet tube on the manifold had folded and closed off the airway)
One solution perhaps if this fails is to put a 3mm sleeve over both nipple and air pipe/tube
From Greymouth NZ

 

[Chris Taylor]

thanks
I cut the tube where it meets the manifold inlet nipple, as it had folded/creased and blocked airflow/vaccum.
My first task is to get the vacuum lines back on to the nipple on the manifold. In your photos you will see they have to expand 2x the diameter- mine seem to have hardened with age so today might try and get a 3mm flexible sleeve to go over the tube and nipple.
The boot opened on mine- Everything locks but except for the boot, but will not unlock.
Its a good feeling when you find the solution- just takes time...

 

[Chris Taylor]

I’ve a feeling you may find that it’s the pump not going into reverse because of the actuator cogs.

If the pump can’t reverse it will only direct the air one way to the system.
Does your pump run, click or make any other noises.

Does the pump run for more than three seconds?

From memory when the pump unlocks the car the actuator goes in and out each time it pump a different circuit.
I think your pump will be similar to mine. I disconnected all the vacuum hoses then used a hand pump (£25 on EBay ) to test each line. From memory the order of locking/ unlocking is... doors, Internal centre glovebox and glasses compartment followed by fuel flap and then boot lock.
As my cogs were not pushing the metal contact effectively the pump was taking 20?seconds of straining to unlock the boot.
If your actuator cogs are not moving the contact in one direction that may be why you can lock but not unlock.

 

[hop3]

Hi
Problem solved. It was either a crack in the manifold ( adjacent the electrics box in the front motor well) or the replacement of the white inlet tubs that had folded at the nipple, effectively closing it off.
Im indebted to the forum and the posts from contributors who pointed me in the right direction. Saved a packet on what would have been an unnecessary vacuum pump purchase.

 

[Chris Taylor]

Well done.

 

[hop3]

Hi
That was a premature email
After working fine on the first day, the opening function has failed again.
Locks everything from the remote.
Pump doesn't run on unlock.
Boot works independently from the remote.
Im going to take the spare pump apart and try to follow your suggestions and see if the cogs need attention. Flying blind on this one, but at least I did get it working when the tube was shortened.
I probably need to understand just how the pump works- are you able to reference a simple explanation for me please? I did try Mr Google but nothing suitable came up.pressue to lock,

 

[Chris Taylor]

Somewhere on this forum there was a thread but it may have been for a different model perhaps a saloon.

I would suggest you take off the outer cover of the pump, then plug all the pipes and cables back in with the pump sitting on the boot floor.
I removed the rubber pipe from the fuel flap actuator so I could block off the end of it when cycling the pump.
(I’m assuming the pump doesn’t unlock when you use the key in the door)
Use the remote to lock and you should see the actuator with the cogs moving as it cycles.
Then see what happens when you press unlock.
With luck by adjusting the cogs you will get it working as I did.

Chris

 

[DawieR]

Hi Guys,
Sorry for jumping onto this thread, but it seems like there is some very good knowledge here and I am in trouble... My only key for my R129 SL500 model 2000 is locked inside the car. Luckily, the boot is open. How can I open the doors via the vacuum pump in the boot?

 

[hop3]

sorry- sounds like a locksmith?

 

[Chris Taylor]

What you may be able to do is remove the pipes from the pump.
Depending what your pump looks like you should to be able to attach a hand pump to the relevant line and either create a vacuum or positive pressure to open the locks.
I’m assuming that there isn’t going to be a deadlock to mess things up.
Being a 2000 I think the pump may look the same as the one I have in which case from memory FT and BFT are the two door locks. The rubber pipe not seen attached to the fuel flap. I think the white is boot popper then the other two are internal compartments and boot lock.

You will need a pump that can give a reasonable pressure to work the actuators.

Chris

 

[LostKiwi]

As above.

 

[DawieR]

View attachment 63037 What you may be able to do is remove the pipes from the pump.
Depending what your pump looks like you should to be able to attach a hand pump to the relevant line and either create a vacuum or positive pressure to open the locks.
I’m assuming that there isn’t going to be a deadlock to mess things up.
Being a 2000 I think the pump may look the same as the one I have in which case from memory FT and BFT are the two door locks. The rubber pipe not seen attached to the fuel flap. I think the white is boot popper then the other two are internal compartments and boot lock.

You will need a pump that can give a reasonable pressure to work the actuators.

Chris

Thanks a lot, Chris. It worked!!!

 

[Chris Taylor]

Brilliant..

I knew the hours I’ve spent in the boot testing would be of use at some point

 

[redmad]

Hi everyone, I purchased a 1992 500SL in the summer which also has problematic central locking (along with wipers on speed 2 only, slight leak from the hard top at both A pillars etc, the usual stuff it seems! But those are for another day!).

At the weekend I went into the boot and removed the boot trim for the battery etc compartment to investigate the pump as from reading this and many other threads on the subject, that seemed to be a good place to start. I could see the yellow vacuum pipes etc but to my surprise... no pump!! All the pipes are disconnected and hanging loose. Presumably a previous owner had a problem with the central locking, removed the pump, then sold the car before replacing it!

Would anyone be able to confirm the relevant part number for my car, details of where and how it is fixed into the car and of which pipe etc connects where on the pump? A photo would be useful, I've had a look at the posts above but can't really tell where and how the pump is fitted given the zoomed in nature of the photos.

Thanks in anticipation, Al

 

[LostKiwi]

Mercedes-Benz Teilekatalog (Ersatzteile online)

mb-teilekatalog.info

 

[redmad]

Mercedes-Benz Teilekatalog (Ersatzteile online)

mb-teilekatalog.info

Thanks very much for that info LostKiwi.