Re: [MBZ] 500SEL hydro suspension still acting up (or down)
Thanks for all the help, guys! I haven't had time to play with the car for a few days, but when I do I'll report back. David wrote: Before worrying about pressure, check the linkages between the height correctors and the control lever inside the car. Since both ends of the car are rising somewhat, and the height is the same (but low), I would check that first. What happens if you raise the lever inside the car? The height control lever inside the car (actually a pull-knob next to the headlight switch---confusingly, it looks just like the parking brake release on a 107) doesn't do anything. I haven't tried disconnecting the linkage to the front control valve and moving the arm manually, which should theoretically raise or lower the whole car---I was putting it off because the linkage is kind of buried between the firewalls at the bottom of the windshield. There is a central pressure regulator, located logically in the pressure circuit so that it controls fluid delivery to the fifth sphere, which is the central accumulator/pressure reserve sphere. On the 6.9 this sphere is on the driver's side adjacent to the suspension sphere. I don't know where it is on a W126. The system is designed around a common working pressure as delivered from that point on. Yeah, I have a fifth sphere in the same place, with an electronic pressure sensor attached. I replaced that sphere when I did all the others. I don't see any specification anywhere for that sensor, which would be nice to have, rather than having to check directly that the sphere is holding pressure (how would I do that anyway, apart from the old stick a pencil in the hole test?). I guess it could have been bad right out the box... apart from the (very basic) schematic in maintenance job 086, you might want to check maintenance job 629, which provides information about how to test system pressures. Importantly, it also shows images of the normal positioning of the height selector linkage at the pressure regulator on the fluid tank. The pics are from a 116; not sure if the 126 is set up the same way, but you might recognise the pieces... Aha! I had missed that one, thanks. Yes, the pictures of the gadgetry on top of the tank look exactly like mine. I'll use that to make sure that the linkages are set up correctly. I hope it doesn't come to having to run through the entire pressure testing procedure, but if it does, the official pressure tester looks like something that could easily be cobbled together with parts from McMaster-Carr. Alex ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] 500SEL hydro suspension still acting up (or down)
On Thu, Jan 6, 2011 at 9:49 PM, Jim Cathey j...@windwireless.net wrote: I find it hard to believe that the hydraulic fluid tank is really a pressure reservoir Can't be, it's plastic. Would explode. Yeah, that's what I thought. The coolant overflow tank is plastic, but then it's not connected directly to a pump putting out 2900 psi. Unfortunately that mistake tends to make me take anything else that Star Motors says about the functioning and repair of the system with a grain of salt. There also seems to be some disagreement as to whether the system constantly recirculates fluid---in which case the health of the pump would be extremely important--- It must. The pump is four radial pistons. It's always pumping. Right, let's stipulate, as our colleague Snook, Esq. would say, that I already knew that. ;) The question I should have posed was, does the main flow control valve allow the high-pressure fluid from the pump to enter the rest of the system (i.e. the level control valves, struts, and nitrogen spheres) at all times? Or does it merely recirculate the pump's output back to its input via the reservoir unless additional pressure to compensate for added cargo weight is required? Which is the case with rear-only SLS? (It's very likely the same answer for both systems, I think.) Oh, and fuel filters can be sintered bronze. Restrictors such as those in the vacuum system, etc. Meaning that there's a reason for that little filter I found inside the flow control valve to be a sintered bronze solid rather than something less exotic, like a fine flat screen, for example? Would soaking it in brake cleaner as I did be enough to restore its degree of restriction, if there is one, to specs? Alex ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] 500SEL hydro suspension still acting up (or down)
Alex Chamberlain wrote: Meaning that there's a reason for that little filter I found inside the flow control valve to be a sintered bronze solid rather than something less exotic, like a fine flat screen, for example? Would soaking it in brake cleaner as I did be enough to restore its degree of restriction, if there is one, to specs? My rear only system has a very fine nylon filter screen in the top of the reservoir, filtering the return fluid before it goes through the reservoir to the pump. When we had those sintered bronze things in carburetors, we used to replace them every time we replaced the spark plugs, or if we had a suspected fuel supply problem. Cost a dollar or less back then. Mitch. ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] 500SEL hydro suspension still acting up (or down)
Meaning that there's a reason for that little filter I found inside the flow control valve to be a sintered bronze solid rather than something less exotic, like a fine flat screen, for example? Well, they're physically robust, small, and cheap. What's not to like? Would soaking it in brake cleaner as I did be enough to restore its degree of restriction, if there is one, to specs? Well, I don't think they're particularly cleanable. That's one thing not to like! Pushing a suitable solvent through in 'reverse' is not too easy on those, especially at a pace that will carry out embedded dirt. -- Jim ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] 500SEL hydro suspension still acting up (or down)
On the rear SLS for my 123 and 124 wagons, the fluid was circulated from the pump to the control valve and back to the reservoir/filter when the engine was running. The control valve decided if additional pressure _on the other side of the circuit which is struts and accumulators_ was needed to maintain the rear axle height. I was surprised at the slow reaction speed of the system. In my opinion, the pump output is low volume but capable of high pressure. The pressure on the working side of the circuit is high. You may need to get yourself a hydraulic pressure gauge and start taking some measurements at different points to determine where pressure exists and where it does not meet spec. I'm still suspicious of your pump. -Max -Original Message- From: mercedes-boun...@okiebenz.com [mailto:mercedes-boun...@okiebenz.com] On Behalf Of Alex Chamberlain Sent: Friday, January 07, 2011 9:46 AM To: Mercedes Discussion List Subject: Re: [MBZ] 500SEL hydro suspension still acting up (or down) On Thu, Jan 6, 2011 at 9:49 PM, Jim Cathey j...@windwireless.net wrote: I find it hard to believe that the hydraulic fluid tank is really a pressure reservoir Can't be, it's plastic. Would explode. Yeah, that's what I thought. The coolant overflow tank is plastic, but then it's not connected directly to a pump putting out 2900 psi. Unfortunately that mistake tends to make me take anything else that Star Motors says about the functioning and repair of the system with a grain of salt. There also seems to be some disagreement as to whether the system constantly recirculates fluid---in which case the health of the pump would be extremely important--- It must. The pump is four radial pistons. It's always pumping. Right, let's stipulate, as our colleague Snook, Esq. would say, that I already knew that. ;) The question I should have posed was, does the main flow control valve allow the high-pressure fluid from the pump to enter the rest of the system (i.e. the level control valves, struts, and nitrogen spheres) at all times? Or does it merely recirculate the pump's output back to its input via the reservoir unless additional pressure to compensate for added cargo weight is required? Which is the case with rear-only SLS? (It's very likely the same answer for both systems, I think.) Oh, and fuel filters can be sintered bronze. Restrictors such as those in the vacuum system, etc. Meaning that there's a reason for that little filter I found inside the flow control valve to be a sintered bronze solid rather than something less exotic, like a fine flat screen, for example? Would soaking it in brake cleaner as I did be enough to restore its degree of restriction, if there is one, to specs? Alex ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] 500SEL hydro suspension still acting up (or down)
Before worrying about pressure, check the linkages between the height correctors and the control lever inside the car. Since both ends of the car are rising somewhat, and the height is the same (but low), I would check that first. What happens if you raise the lever inside the car? What happens if you add load to one end or the other? Does the car adjust? As to pressure: I do not know for sure, but I imagine that the pressure management aspect of the system is as much a copy of Citroën's system as is all the rest, therefore: There is a central pressure regulator, located logically in the pressure circuit so that it controls fluid delivery to the fifth sphere, which is the central accumulator/pressure reserve sphere. On the 6.9 this sphere is on the driver's side adjacent to the suspension sphere. I don't know where it is on a W126. The system is designed around a common working pressure as delivered from that point on. This allows the pump to be variable output (with RPM). Extra fluid is simply routed back to the reservoir without pressure. Look for the place where the largest reservoir return line originates. This will be the pressure regulator (the line must be able to handle full pump flow, unlike the suspension element return lines which only handle leak-by). The pressure regulator (again, I'm talking about Citroën, you'll need to verify the MB implementation) has a ball valve and a calibrated spring. There's also an adjustment screw to set the relief pressure. NOTE: an under-pressure reserve/main accumulator sphere can weaken/damage the pressure regulator valve if there's too much cycling of the valve. You should test overall system pressure as measured on the CONTROLLED side of the regulator valve, and verify the gas pressure in the central accumulator. Those are the most important numbers. D. On 1/6/2011 12:55 PM, Alex Chamberlain wrote: But the car, though at the same height front and back, won't rise to normal ride height overall. It's too low all the way around, by about three inches; Any suggestions appreciated! Alex ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] 500SEL hydro suspension still acting up (or down)
You want the ride height hydraulics to be slow response, otherwise they would be chasing all kinds of bumps and what not and the car would be gyrating all over the place. Sort of a built-in analog filter. Now that might be different for the shocks that keep the wheels planted, that is a different kettle of ducks. --R On 1/7/2011 11:10 AM, Max Dillon wrote: I was surprised at the slow reaction speed of the system. In my opinion, the pump output is low volume but capable of high pressure. The pressure on the working side of the circuit is high. -Max ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] 500SEL hydro suspension still acting up (or down)
Alex Chamberlain wrote: Right, let's stipulate, as our colleague Snook, Esq. would say, that I already knew that. ;) The question I should have posed was, does the main flow control valve allow the high-pressure fluid from the pump to enter the rest of the system (i.e. the level control valves, struts, and nitrogen spheres) at all times? Or does it merely recirculate the pump's output back to its input via the reservoir unless additional pressure to compensate for added cargo weight is required? Which is the case with rear-only SLS? (It's very likely the same answer for both systems, I think.) I can only speak as an authority on the S123 system... The pump output goes into a hose with a anti-cavitation restriction in it and then into the hardline that connects to the valve inlet. Unless the valve is positioned to supply pressure to the struts (I'm lumping the accumulators in the the struts 'caues for this discussion they work as a team), the inlet flow is routed to the return line. If the valve is positioned to release strut pressure, the strut oil plus the pump oil is returned to the tank. The only filter is on the return flow as it enters the tank. This means most of the time the only place there is any significant pressure is between the pump and the anti-cavitation piece, and between the valve and the struts. The rest of the system is just flowing. I suspect that is how the other systems work also - but that's just a guess. I have photos of the insides of the S123 pump and valve if anyone cares. -- Philip ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] 500SEL hydro suspension still acting up (or down)
Agree with all below, and add that the control valve is supposed to maintain a factory-set base pressure on the strut/accumulator side, regardless of the position of the lever. This base pressure is the required pressure to keep the rear end from sagging when the car is in ready to drive condition (i.e. no cargo, but full fuel tank, spare tire and tools in place). If the system is operating correctly, the only way to relieve the base pressure is by opening the bleed screw on the control valve or make a leak in one of the lines to/from strut and accumulator. -Max -Original Message- From: mercedes-boun...@okiebenz.com [mailto:mercedes-boun...@okiebenz.com] On Behalf Of Fmiser Sent: Friday, January 07, 2011 1:10 PM To: Mercedes Discussion List Subject: Re: [MBZ] 500SEL hydro suspension still acting up (or down) Alex Chamberlain wrote: Right, let's stipulate, as our colleague Snook, Esq. would say, that I already knew that. ;) The question I should have posed was, does the main flow control valve allow the high-pressure fluid from the pump to enter the rest of the system (i.e. the level control valves, struts, and nitrogen spheres) at all times? Or does it merely recirculate the pump's output back to its input via the reservoir unless additional pressure to compensate for added cargo weight is required? Which is the case with rear-only SLS? (It's very likely the same answer for both systems, I think.) I can only speak as an authority on the S123 system... The pump output goes into a hose with a anti-cavitation restriction in it and then into the hardline that connects to the valve inlet. Unless the valve is positioned to supply pressure to the struts (I'm lumping the accumulators in the the struts 'caues for this discussion they work as a team), the inlet flow is routed to the return line. If the valve is positioned to release strut pressure, the strut oil plus the pump oil is returned to the tank. The only filter is on the return flow as it enters the tank. This means most of the time the only place there is any significant pressure is between the pump and the anti-cavitation piece, and between the valve and the struts. The rest of the system is just flowing. I suspect that is how the other systems work also - but that's just a guess. I have photos of the insides of the S123 pump and valve if anyone cares. -- Philip ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] 500SEL hydro suspension still acting up (or down)
As long as it is clear to everyone that the post that Max is commenting on below applied to spring-assisted SLS systems (123/124 wagons and similar). The 6.9/Euro-500SEL system is QUITE different, with no steel springs. The pressure management is also different, and there's not necessarily a base pressure in quite the same sense as in the steel spring systems. Alex: apart from the (very basic) schematic in maintenance job 086, you might want to check maintenance job 629, which provides information about how to test system pressures. Importantly, it also shows images of the normal positioning of the height selector linkage at the pressure regulator on the fluid tank. The pics are from a 116; not sure if the 126 is set up the same way, but you might recognise the pieces... D. Max Dillon wrote: Agree with all below, and add that the control valve is supposed to maintain a factory-set base pressure on the strut/accumulator side, regardless of the position of the lever. This base pressure is the required pressure to keep the rear end from sagging when the car is in ready to drive condition (i.e. no cargo, but full fuel tank, spare tire and tools in place). If the system is operating correctly, the only way to relieve the base pressure is by opening the bleed screw on the control valve or make a leak in one of the lines to/from strut and accumulator. -Max ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] 500SEL hydro suspension still acting up (or down)
This posting on the M-100 6.9 forum may also be helpful: http://www.m-100.cc/forum/topic.asp?TOPIC_ID=5862 ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] 500SEL hydro suspension still acting up (or down)
Sell it to a Mexican as an exotic low-rider! Don't take it to a shop, on that Top Gear with the 600Grosser his checkup repair bill was 15k pounds! --R On 1/6/2011 12:55 PM, Alex Chamberlain wrote: But the car, though at the same height front and back, won't rise to normal ride height overall. It's too low all the way around, by about three inches; Any suggestions appreciated! Alex ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] 500SEL hydro suspension still acting up (or down)
Check for a filter at the base of the reservoir. If you do have one there and it's full of crud, you may not be delivering enough fluid. I would double-check the o-rings on the filter, and apply some gentle air pressure from the back side of the sintered filter to make sure it's allowing fluid through. Could be clogged, and that would account for the low riding issue anyway. So could a stuck pressure relief on the pump, for that matter -- no fluid delivery! You might want to bleed it a bit too -- open a fitting slightly on the front or rear and verify that you get fluid flow while the engine is running. Peter ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] 500SEL hydro suspension still acting up (or down)
On Thu, Jan 6, 2011 at 4:19 PM, Peter Frederick psf...@earthlink.net wrote: Check for a filter at the base of the reservoir. If you do have one there and it's full of crud, you may not be delivering enough fluid. There's a filter inside the reservoir which I replaced, although it didn't seem to need it. The low-pressure line at the bottom of the tank going back to the pump is clear. I would double-check the o-rings on the filter, and apply some gentle air pressure from the back side of the sintered filter to make sure it's allowing fluid through. Could be clogged, and that would account for the low riding issue anyway. That's a good thought. (So that's what that material the filter is made of is called! I'd only ever heard the term sintered applied to ceramics before.) So could a stuck pressure relief on the pump, for that matter -- no fluid delivery! Makes sense; another reason to check the pump for pressure and replace it with another used unit if necessary. You might want to bleed it a bit too -- open a fitting slightly on the front or rear and verify that you get fluid flow while the engine is running. That I've done. There is some fluid flow, at both the front and rear bleed valves, and it was clear and free of air bubbles, although not the dangerously high-pressure spray that I was expecting. Possibly a clue there. Alex ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] 500SEL hydro suspension still acting up (or down)
I find it hard to believe that the hydraulic fluid tank is really a pressure reservoir Can't be, it's plastic. Would explode. There also seems to be some disagreement as to whether the system constantly recirculates fluid---in which case the health of the pump would be extremely important--- It must. The pump is four radial pistons. It's always pumping. Oh, and fuel filters can be sintered bronze. Restrictors such as those in the vacuum system, etc. -- Jim ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
