R129 1991 500SL

How do I fix it?

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Keith R129

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Hi, my cars suspension is at rock bottom. It's that low I can't drive it on the road. I know I have leaks so I will fix them first. Does anyone know the next step in bleeding the system to get my suspension working again?
 

LostKiwi

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Hi and welcome.

I'm assuming you have ADS in which case I believe it self bleeds. You may need STAR to exercise it to do this.
 
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LostKiwi

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This may be useful...
 

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Keith R129

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Hi LostKiwi, thank you for your assistance. My ADS lamp on the dash doesn't come on when I turn the ignition on, possibly a bulb. Also when I try for an error code on pin 9 (I have the 16 pin) I get no reading at all. I have checked for leaks and can't find any from the distribution valve. Not sure what's going on. I have read sections that say you have to bleed the system and others that say it is self bleeding. One hint though, the oil level got very low so could have run dry before I filled it up. I guess that means I do have a leak somewhere. I'll keep looking.
 

Richard Moakes

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If the oil reservoir level was low, you either have a major leak, or more likely the accumulators have lost their gas pressure and are now filled with fluid.

It sounds like the ADS module has no power, no MIL or diagnostics suggests it’s been disconnected from power.

Is fluid flowing back into the reservoir with the engine running?
 

Richard Moakes

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Hi and welcome.

I'm assuming you have ADS in which case I believe it self bleeds. You may need STAR to exercise it to do this.

ADS1 can get itself into a state where it will not self bleed, there is an internal bleed screw on the main valve.
 
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Keith R129

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If the oil reservoir level was low, you either have a major leak, or more likely the accumulators have lost their gas pressure and are now filled with fluid.

It sounds like the ADS module has no power, no MIL or diagnost
ADS1 can get itself into a state where it will not self bleed, there is an internal bleed screw on the main valve.

ics suggests it’s been disconnected from power.

Is fluid flowing back into the reservoir with the engine running?


Hi Richard, funny you mention about the fluid flowing back, no there is nothing going back to the reservoir.

Keith
 

Richard Moakes

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Sounds familiar!

Find the high pressure line from the back of the tandem pump to the ADS valve and disconnect it from the valve. Place the open end in a container and add ZH-M fluid to the reservoir. Start the engine and rev it to 25 or until fluid flows from the line. It’s low flow rate but high pressure so quite safe.

Once you have established flow, reconnect the line to the valve and restart. Check for fluid return to the reservoir.

This should bleed the pump and establish a flow. Once this is done the suspension may rise or you might have to bleed the main ADS valve.
 
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Keith R129

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Sounds familiar!

Find the high pressure line from the back of the tandem pump to the ADS valve and disconnect it from the valve. Place the open end in a container and add ZH-M fluid to the reservoir. Start the engine and rev it to 25 or until fluid flows from the line. It’s low flow rate but high pressure so quite safe.

Once you have established flow, reconnect the line to the valve and restart. Check for fluid return to the reservoir.

This should bleed the pump and establish a flow. Once this is done the suspension may rise or you might have to bleed the main ADS valve.
Thank you Richard, you are a godsend. I'll give that a try and see how it goes. I'll keep you posted.
 
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Keith R129

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Thank you Richard, you are a godsend. I'll give that a try and see how it goes. I'll keep you posted.
I have several manuals for the car but i'm yet to find a diagram that has an exploded view of the distribution valve so I know which pipe to disconnect. All diagrams I have found are not very clear. I wish I had a pit. It would make life easier.
 
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Keith R129

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Hi again Richard.
I have tried to follow the lines from the steering pump but can't find the one that goes to the distribution valve. I can't find documentation that tells me where each pipe goes. Here is a pic of my valve which wasn't leaking.
 

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Richard Moakes

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The line you are looking for is a flexible line running from the tandem pump on the left side of the engine, under the engine sump and round to the ADS valve, it converts to hardline before it connects. If I remember right, you can split the line at a fitting rather than disconnect from the valve, but it was a long time ago. I do know the port on the main body of the valve is marked "P", not to be confused with the "P" port on the levelling valve which is attached to the main valve.

Lots of good info here https://www.benzworld.org/forums/r129-sl-class/2939297-ads1-ride-height-issue-non-us.html

Take a look at the attached photo, notice the hex bar on the right hand side of the picture, this is what you gently unscrew, but not remove from the main valve to bleed it internally.

getmedia.ashx
 
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Keith R129

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The line you are looking for is a flexible line running from the tandem pump on the left side of the engine, under the engine sump and round to the ADS valve, it converts to hardline before it connects. If I remember right, you can split the line at a fitting rather than disconnect from the valve, but it was a long time ago. I do know the port on the main body of the valve is marked "P", not to be confused with the "P" port on the levelling valve which is attached to the main valve.

Lots of good info here https://www.benzworld.org/forums/r129-sl-class/2939297-ads1-ride-height-issue-non-us.html

Take a look at the attached photo, notice the hex bar on the right hand side of the picture, this is what you gently unscrew, but not remove from the main valve to bleed it internally.

getmedia.ashx
Hi Again, I found the bleed hex bar as well as the bleed nipple on top. I put a hose on the nipple, undid the hex nut one turn and then opened the bleed nipple. A fair bit of rather brownish oil came out. I don't think that it's meant to be that colour. From reading other posts I then attempted to bleed the system by tightening up the nipple and raising the lever to Fill with the engine running, Nothing happened. I think my pump might be the problem but wouldn't that stop the power steering from working as well? It could just be a blockage. What would you recommend please Richard?
 

LostKiwi

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The pump is a tandem pump - 2 pumps in a single body sharing a single reservoir. Beyond that they're separate systems.
 
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Keith R129

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The pump is a tandem pump - 2 pumps in a single body sharing a single reservoir. Beyond that they're separate systems.
So the reservoir on top of the pump is different to the reservoir on the front of the car for the suspension? That's where my problem is. There is no fluid being pumped to the suspension.
 
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Keith R129

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The pump is a tandem pump - 2 pumps in a single body sharing a single reservoir. Beyond that they're separate systems.
Hi Again, I am slowly getting there. I understand where everything is now and the procedure. Any ideas as to why I get no reading at all from the diagnostic reader on pin 9 and why the ads dash light doesn't work? I figure I need to fix that before bleeding the system.
 
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Keith R129

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Sounds familiar!

Find the high pressure line from the back of the tandem pump to the ADS valve and disconnect it from the valve. Place the open end in a container and add ZH-M fluid to the reservoir. Start the engine and rev it to 25 or until fluid flows from the line. It’s low flow rate but high pressure so quite safe.

Once you have established flow, reconnect the line to the valve and restart. Check for fluid return to the reservoir.

This should bleed the pump and establish a flow. Once this is done the suspension may rise or you might have to bleed the main ADS valve.
Hi Again, sorry to be a pain. I disconnected the high pressure line and ran the engine at 2500 for about 30 seconds. No fluid at all. Still no fluid going back to reservoir. Prior to this I bled the distributor valve and oil came out yet no drop in the reservoir. Could there be a blockage somewhere? Not sure where to go from here.
 

LostKiwi

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Not sure about ADS but ABC pumps lockout when they detect a pressure loss on the outlet. To get them to pump again you need to pressurise the reservoir to around 6psi. When I had to do mine I made up a cap using an old wine cork trimmed to fit the didstick hole with a needle type inflator hooked to a bicycle pump.
 

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