300TD W123 rear suspension

[100haggis]

Hello all,
Apologies for any errors but I'm a newbie. I've bought a 300Td which has a few issues but the first is with the self levelling suspension. The rear end bounces quite a bit as if the shockers are knackered but before I dive in and replace them how do I give the system a check over to make sure it's actually working? Can normal shocks be fitted and make the self levelling obselete? Also my central locking is playing up. The door buttons come up slowly as you drive but they never go down on the key. Could this be an air leak issue and if so where should I start looking? I have a haynes manual for the car which doesn't have much detail, are there better service manuals available to Joe Public?
Cheers
Matt

 

[simon_wall69]

To check the self-levelling works put something weighty in the boot (child or wife?) and see if the back of the car rises. You can replace the self-levelling suspension with normal springs and this is what a lot of people have done.

The central locking is a vacuum issue. There are loads of threads on this but it generally comes down to replacing pipes. The vacuum tank is next to the fuel tank and the vacuum pipes are all over the car. The vacuum pipes tend to go where the pipes go into the doors.

 

[100haggis]

Cheers Simon,
Should the car be idling when I get my missus to clamber in the boot or would some revs help get thimgs going? Also if I was to ditch the self levelling do you know of part numbers etc for standard suspension kit and if there are any MOT implications down the line?
Matt

 

[Number_Cruncher]

>>The rear end bounces quite a bit as if the shockers are knackered...

First things first - the devices which look like shock absorbers or dampers *aren't*. They are simply hydraulic rams. If you replace these, it will not fix your problem.

The damping (and supplementary springing) is done by the nitrogen filled spheres (almost Citroen like devices) which are fitted inboard, and connected to the hydraulic rams by a large bore pipe. The spheres have failed on your car, and need to be replaced.

>>Can normal shocks be fitted and make the self levelling obselete?

Don't do it!! Seriously, please dismiss this option from your mind! Most who have converted have regretted it. The self levelling system is simple, and once fixed it rides really well.

More here: http://www.mbclub.co.uk/forums/showthread.php?t=60029

>>if so where should I start looking?

You need to check the system for vacuum tightness. The first thing you need is a tool, a mityvac which can both suck and blow, and has a gauge. Without this tool, you'll never find and fix all the leaks.

 

[100haggis]

Thanks for all the advice Number Cruncher,
The more I drive the car the more I think I'll need to tap into the expertise of fella's like you! Do you know if the parts needed for the rear suspension overhaul are only available from MB or are there reputable (and no doubt cheaper) alternatives?
Matt

 

[Cosworth]

ref the central locking, you will need to check the central locking units in each door, including the fuel filler cap device.

You will find either a white or blue unit and you must check the rubber boot on that as it wears out and splits. Thats the part you will need to replace.

ref the rear suspension, you must first check, do you have any fluid in the resovior tank.

Also check for leaks near the rear shocks, if there are no leaks you may need to change the accumilators. There are two and both will need changing.

 

[stever]

ref the central locking, you will need to check the central locking units in each door, including the fuel filler cap device.

You will find either a white or blue unit and you must check the rubber boot on that as it wears out and splits. Thats the part you will need to replace.

That's my experience too. Luckily the spares are not expensive, and it's unlikely that they're all broken. Coupe owners should note thaat there are also two diaphragms to check under each of the front seats.

 

[100haggis]

Got the spheres sorted on friday and the car rides like a dream now! Got genuine MB parts through GSF car parts in Bradford at nearly half price! Thanks to all for your advice, to have ditched the self level system would have been madness.
Cheers
matt