Suspension filter

[Oversize]

Hi everybody. I'm new to the forum so my L Plates are definitely on! I did my apprenticeship with MB back in 1988, but never had the chance to replace the suspension filter on a 6.9. Wondering what's the simplest method? Any help would be appreciated....

BTW I haven't been able to resist a neglected 6.9 & as a result I now have 2! One's only good enough for a parts car but the other I plan to use as a Sunday driver. They're both the same light blue (906) so I'm calling them the terrible twins......

4248
5298

Yeah I know every 2nd number is the same (I dunno how I managed that)!

 

[TJ 450]

Hi Oversize,

To replace the filter requires removing the main valve unit from the top of the reservoir. This also means undoing the flare nuts, and it is also worthwhile cleaning out the strainer in the valve/regulator unit as well. While you're there, you might as well remove the reservoir and clean that out, replacing the low pressure feed hoses too.

The filter is held in place by a spring that hooks into the body of the main valve assembly. To remove, you push and turn the filter/spring. This is much like the springs that secure the parking brake shoes, on a larger scale.

Then you won't have to worry about it for years.

Tim

 

[WGB]

The reservoir is designed so that the intake doesn't draw from the very bottom of the reservoir but via an angled tube that leaves about a litre of fluid undisturbed in the bottom of the reservoir.

This litre of oil and the filter gradually turn black with rubber from the system even though the oil on the dipstick will be so clear as to be hard to see on the dipstick - so I guess it is an efficient way of removing sediment.

The filter itself is at the end of the return line into the reservoir and is held by a spring clip arrangement that allows it to open if it gets blocked.

To completely change the fluid you would need to remove the struts and blow through all the lines and there is no recommended service procedure. This is not a very practical procedure and like servicing an automatic transmission it is more practical to change most of the oil and clear out the sump.

I think a practical servicing procedure is to raise the car to depressurise the system and then lower it so that the rams are largely emptied back into the reservoir. At this point the reservoir is removed from the car and emptied and cleaned of its black gunge and the filter changed.

The reservoir is then replaced with a new piece of hose attached to the bottom of the reservoir to the inlet of the pump and the reservoir filled with oil. The outlet hose from the pump is left disconnected and the end is aimed into the filler hole of the reservoir so that the engine can be started and the pump bled. After a short run the pump will flow free from air and the motor can be turned off and the pump outlet hose reconnected.

The car can then be raised on it's own pump and at that point about 4 litres out of the 5 in the system have been replaced and all the crap has been removed from the system. This is a better percentage than most automatic transmision oil changes but if it is not considered sufficient and you have appropriate lifting gear extra oil can be bled either from the front and rear bleed nipples or by loosening unions and pressurising the system.

I used genuine M-B hydraulic oil for my car which varies in price from AUD$25-30 per litre up to over $60 from a main dealer.

Bill

 

[Styria]

Hi Oversize, both TJ450 and WGB have given you a pretty thorough description of what to do, and how to do it. It just needs to be remembered that there is no way that you can remove the hose on the bottom of the tank unless it has been removed from the car. BTW, is there any particular reason that makes you think that the filter requires changing ?

As a matter of interest, which of the two cars is the parts car ? I hope you will enjoy your stay on our website and I look forward to you taking an active part. Regards Styria

 

[Oversize]

Thanks for everyone's input. I know it's not applicable to me now, as both cars have been lacking maintenance for many years, but has anyone tried removing the main valve (with the filter attached) without removing the distrubution valve (and having to undo all the pipes). As part of a normal servicing schedule, it seems much quicker to change the filter... However, exploded diagrams I've seen suggest there's 2 very small O ring seals between the main valve & distrubution block. Changing the filters was much easier on the 126s (only 2 fittings to undo) & the 6.9s had me scratching my head. What's the best way to thoroughly clean the tanks once removed? I might even apply the same method to the engine oil tanks. Styria, the main reason for a change is I have no idea when the filters were last replaced. The parts car (4248) is very slow to pump up after sinking overnight (another problem). I suspect the strainer (if still fitted) is almost completely blocked.

 

[WGB]

The replaceable filter is only on the return line so shouldn't affect the speed of pump up too much.

There is a very small brass conical filter that is supposed to be fitted in the pressure line where the pump outlet enters the distribution valve but my car for one is missing it.

How slow is slow when it comes to pump up time?

One very useful advice that Styria gave me when I purchased my 6.9 was to purchase a good set of "flare joint" spanners - it has made work on all parts of the hydraulics not only safe but a breeze, with no rounded off fittings and nothing stripped so long as you are careful and start all threads by hand.

Bill

 

[Styria]

Hi Oversize, there is a bit of a trick involved in relating to the removal of the pressure regulator, and separation of the valve block from that part. You will notice, once you have separated the block from the regulator, that there is only one rubber 'O' ring. The valve block is attached to the regulator by means of two fairly long 10mm bolts. Naturally, you'll have to undo those, obviously and preferable with the disc in the "Maintenance position", but it is the bracket that secures the cable that stops you from moving the disc to that position.

So initially I don't touch the disc. I undo the two bolts, and remove them, and also remove the cable bracket, but all that time holding the valve block hard up against the pressure regulator. Once you have removed the bracket, then by all means move the disc to the maintenance position. Regarding the various pipes, I only ever disconnect the main oil feed hose and the short double bended steel pipe that leads to the immediate brass junction block. It is not necessary to undo or remove any steel lines that feed to the alloy block.

Regarding removal and cleaning of the tank - you need to move the hose on the bottom of the tank as one unit - assembly and disassembly (fitting and re-fitting ) are carried out on the bench. Cleaning - any cleaning product - kero, petrol, degreaser and compressed air. It'll take several application, as the sediment is stubborn. Hope all that helps. Regards Styria

 

[Oversize]

Hi All,

Bill 5298 is much faster than 4248, but I've never actually timed them. If jacked up & depressurized I'd take a guess at 5-10 minutes. I suspect the conical screen is blocked and there's only one way to find out... Of course leaking front & rear control valves won't help pump-up speed. I wouldn't even attempt a job like this without flare nut spanners as they're usually super-tight.

Styria that does help a lot & it will be clearer when I start the job. I do have a parts washer filled with kero & a compressor, but like the engine oil tank it'll be almost impossible to thoroughly clean the inside. In the beginning, i'll try a long screwdriver for the worst of it. Has anyone tried ultrasonic, or some other type of non-acidic industrial cleaning? I've even heard people using a dishwasher (obviously not the one in the kitchen)!

Regards, Mark

 

[Styria]

If all components in the system work well, pumping up should be achieved within a matter of no more than one minute, and not having to rev the devil out of the engine. To "help things along" a bit, I leave the cable disconnected from the disc - thus, once the engine is started, one can move the disc freely from the normal to high position, and by not being restricted by the cable, it is very easy to tell if there is pressure in the system. Regards Styria

 

[WGB]

Working on the principle that a 6.9 has to be driven to keep it in good condition mine is used at least once per week.

Usually it will not settle completely in a week and most times the low pressure suspension light never comes on at startup.

If it does it takes about 15secs of an idling engine to go out and another 15 seconds to lift the car.

Part of the hydraulic integrity and rapidity of response must belong to how effective the central sphere is as this should store some pressure until various leaks in struts and valves allows it to deflate.

Equally if the car is not used a lot there must be a chance that air could be drawn into the system and I know when the system is opened for repair it can take a week or two before it really settles down and starts behaving on it's best behaviour.

Bill

 

[Oversize]

Geez was my first post only 8 years ago? Means I had some cars for around 5 years before I started reaching out for info...

 

[Michel]

Geez was my first post only 8 years ago? Means I had some cars for around 5 years before I started reaching out for info...

You only joined TK 8 years ago

 

[Styria]

Mark is making up for it now - he is. Going like a steam train. Whilst I have not commented at this stage, I have been greatly impressed and enjoyed his organization of the 6.9 40th anniversary run and all the photos that were posted on TK. An absolutely splendid effort. Regards. Styria

 

[Oversize]

Thanks for the kind words of encouragement! Funny that after all this time I feel like I’m just getting started!

 

[Styria]

Yeah Mark, it can affect you that way...........Keep posting. Regards Styria