my 6.9 can't get it up !

[TJ 450]

I would be performing an exhaustive examiniation of the suction side as any air getting in will cause the fluid to drain back to the tank and the pump will not prime unless that high pressure hose is removed again.
In particular, check out the fitting at the base of the pump and its hose and even the pump's cover itself for near perfect sealing. How are the suction side hose looking?

Regards,
Tim

 

[s class]

Ha - so I was so proud how trusty tusty has stayed up for a month - not more than a few mm droop in the front. before starting it today, I pushed down on the front like oyu would check the shocks in a regualr car - and it was still firm, not going mooshy from loss of pressure. I was impressed. From this I conclude that the struts and levelling valves are goof. I started the car, and found the warning light would not go out. Even revving to 3000rpm for a little bit didint help. So I got out the 17mm spanner, and sure enough, when I disconnected the high pressure line from the pump to the pressure regulator - lots of air. I bled it out, reconnected, and the warning light went off almost immediately. THis is frustrating - I know this means there are leaks on the suction side, but its not spotting oil on the floor at all. I guess I'll just have to go over all those clamps again.

 

[B13]

I'll be keen to hear the results of your findings.

Ian.

 

[B13]

WGB wrote (in the other thread):

You and Des sure have had a lot of trouble with that car's suspension and I offer my sympathy but the answer must be there somewhere.

Is it still down at the front?

Might be a time for another posting ofteh problems and try again with some collective wisdom.

Yeah why not... here's an update.

When the weather heats up and car lifts to normal height... like today... it was 30 degrees and the car looks just about right. The suspension light still doesn't go out, and the distribution valve plate just turns freely with no feel in the detents.

In the cold (Nov and Dec in Melbourne have been pretty much under 25 degrees except for the odd day over 30) the car won't lift and if I load it up with people or freight it will sink at the back, sometimes quite severely and won't self level. Even then after removing the people/freight - thank god I drive this car for the most part solo without passengers- it takes ages (like days, not just a long 1hr drive), but a hot day to bring it back up to normal height.

About a week ago I disconnected the high pressure hose from the pressure regulator and pointed it into the reservoir to double check the pump is providing good volume, which it is, even at idle.

Loosening the hex nut and/or the large 19mm nut on top of the pressure regulator with the engine running doesn't produce much in the way of hydro fluid coming out (I thought there would be copious amounts under considerable pressure) so I have no idea where the fluid is going... If it was going straight back to the tank then looking down the filler into the tank with the engine running I thought there would be considerable motion on the surface of the hydro fluid, however what I see is hydro fluid sitting like a calm pond - no descernable motion whatsoever.

I've been reading a book which came with my car called Aus Model Year 1979 which has a very extensive section on the hydro setup and I can't help but think that the central sphere circuit isn't properly pressurising and thusly the distribution valve isn't able to send the fluid to the required level controllers. The reason the car doesn't sink to the ground is some check balls have come into play and the hydro struts are pressurised well enough to not let the car sink. Where that theory falls apart is that on warm ambient temperature days the car will more than likely lift to its proper height.

As always this is my only daily driven car so any work I undertake has to be able to be done on a weekend and I can't disable the car like I did in October. My next annual leave is in Feb which I intend to spend sorting this out, or looking at springs.

Ian.

 

[s class]

The symptoms still suggest you don't have enough pressure in the primary circuit (pump -> pressure regulator -> 5th sphere -> distribution valve).

The pressure sensor - is it correctly installed on the 5th sphere sandwiching the approx 20mm thick block which has a port in it for one of the hydro lines? I ask because any butchering there could be impeding the fluid flow. Have you checked all the steel lines in this primary circuit to ensure none are pinched?

Support the car, depressurise the 5th sphere, and then remove that little gold filter from the back of the pressure regulator. I know you have done this, but maybe the system has debris in it that is taking time to clear, and has re-clogged the filter. Is there any rust visble when you remove that filter? The steel lines in the primary circuit could also be clogged with rust. They are simple enough to remove and blow air through.

I don't want to see you put springs in this car. Hell, if I had the cash spare I'd pop round and lend a hand.

 

[WGB]

A few observations

1) the detent plate is not under pressure if it spins freely.

Under pressure it gets harder and harder to move and when we looked at Liamerc's 6.9 with flat spheres it had little fluid in the reservoir (all the fluid was in the collapsed spheres), normal ride height and the detent plate was jammed solid.

2) If there is no pressure the pumped fluid is not getting through at adequate pressure which means a line problem, a pump problem or a blocked filter.

3) I guess there may be something weird that can happen with the reservoir valves.

I'll go to bed tonight with the hydraulic manual; and see if I can think of anything else.

I bet it's a simple little problem when it's found.

Bill

 

[WGB]

Just an observation - I have occasionally after servicing my car pulled the disc to the normal position (or thought I had) and on driving the car the next day it will drive normally but the light comes on and the car slowly sinks (over several hours) and won't pull itself back up.

On checking the disc plate there was about 1 to 2 mm of movement before it went into the "N" position completely then the car suddenly sprang back to life with a short hiss and all worked normally.

This sounds a little like what is happening to you and maybe the reservoir valve body is not completely in the N position (Due to wear or adjustment) but running effectively at the very end of the S position and the pump pressure is being partly bypassed - as this is what seemed to happen with my car.

I don't know what manuals you have

I can e-mail the 22 page document "Hydropneumatic Suspension - Functional Description" which gives the system in detail - so long as your e-mail will take 8 or 9 megs.

I also have a short simplistic document put out by Star Motors NY which has a succinct page on Hydraulic Suspension Diagnostics which I will e-mail to you anyway.

Bill

 

[B13]

Can someone tell me this, when the system is working properly and you change the height from normal height to the higher setting, what is lifting the car? The hydro pump or the central sphere?

I.

 

[WGB]

The central sphere is but if the motor is running the pump will assist.

The central sphere should be able to lift the car even without the motor running as far as I know and is a useful test for the viability of the central sphere but if your system is never pressurising properly in the first place it will not act properly even if in good nick.

I don't know if you found that literature useful but the valving is described in quite a lot of detail and I still think one possibility is a problem with the pressure regulator on the reservoir so long as the pump is pumping.

It may come to a pressure gauge with a T-piece to track down where the pressure is being lost.

Bill

 

[Des]

Is it possible that one or more of the sphere's were fitted incorrectly or are faulty?

I.e. fitted in the wrong order to the car, as there are different pressures for front/back

 

[B13]

Is it possible that one or more of the sphere's were fitted incorrectly or are faulty?

I.e. fitted in the wrong order to the car, as there are different pressures for front/back

The thought had crossed my mind... and I haven't really checked, figuring Carl to be something of an MB expert...

No high pressure hoses under the car leak from the connections so i can presume they've been fitted properly...

Still need to check that the correct coloured dot spheres are in the right place and what manufacturer they are, as I believe some are better than others.

Also need to buy some more trolley jacks as the more I read into technical side of performing maintenance on the system the more it is obvious that I need to get all 4 wheels off the ground to properly depressurise the system and start diagnosing. With my current equipment i can get 2 wheels off the ground but not all 4. Well i could probably do all 4 but it would make life easier if I had 4 trolley jacks.

I.

 

[abl567]

I will assume you don't work on the car supported only by trolley jacks.
Jack stands are not expensive and simply essential for basic safety.

 

[B13]

I have jackstands, ramps, a trolley jack... like most car enthusiasts have.

Its just when they say to lower the car so that the wheels are on the ground and start the car and let the suspension energise, it would be far easier to do with a series of trolley jacks rather than jack stands.

I.

 

[s class]

I don't think that sphere problems (or their incorrect location) cold cause these symptoms. Like Bill, I was going to suggest that you need to tee in a pressure guage after the pressure regulator.

 

[B13]

Pictures from today.

This is about the height I would like the car to be:

Today was 20 degrees but yesterday was 30 degrees so the car lifted. Its still up as a result of lifting itself in the heat. It may stay like this for a little while, or until I put more than one person in it or some freight in the boot.

Front-on shot:

Needless to say the warning light is still on.

I.

 

[s class]

The fact that once the casr is up, it stays up for a reasonable time comfirms that the struts and two levelling valves are good. This observation can also be extended to confirm that the problem therefore lies with either the pressure regulator, pump, or the distribution valve.

the pressure regulator and pump combo could be guilty of not making sufficient pressure. A gauge will confirm this.

The distribution valve could be guilty of bypassing fluid back to the reservoir.

The distribution valve has three needles in it. They are tapered. Could it be that someone has inserted them back the wrong way after a cleaning effort?

 

[WGB]

Agree with S-class that the problem sounds like it is in the pump/regulator area.

Either the pump is not pumping at correct pressure or the regulator is bleeding it back.

I thought you said you had replaced the regulator/valve on the top of the reservoir in an earlier post.

Bill

 

[B13]

I have.. a good used one. I'll put the old one back this weekend.

I.

Agree with S-class that the problem sounds like it is in the pump/regulator area.

Either the pump is not pumping at correct pressure or the regulator is bleeding it back.

I thought you said you had replaced the regulator/valve on the top of the reservoir in an earlier post.

Bill

 

[WGB]

Did the problem change after you changed the regulator last time?

I thought the original problem had more to do with the front not pumping up rather than the whole system not pumping as a whole.

I know the pump has been replaced a couple of times and one hopes that it is now pumping at a reasonable pressure.

If the general problem of low pressure only started after the regulator was changed I wonder if you have a mixed problem of faulty regulator (The new one) and a faulty distribution valve (the old one).

If this is the case the two components can be split and recombined with the old regulator and the new distribution valve and a new o-ring between them.

Just a few idle thoughts and I might be barking totally up the wrong tree - I guess the first thing to do is change entire units and see what happens.

Bill

 

[B13]

The change made no difference but it was early on before changing the pump. Since its not a lot of effort to change the PR/DV and the car doesn't sink while doing it this sounds like a sensible place to start this weekend, armed with some new O rings.

Looking at the schematic diagram, with the PR/DV removed I have access to the hoses going to the central sphere so might try to blast some compressed air thru them...

I.