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
