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Can pressure relief valve cause hydraulic fluid reservoir to overflow/spit out fluid?
I had front and rear valve blocks rebuilt, and replaced all 4 accumulators incrementally. A rear hose blew after I replaced the front valve block and accumulator. I then replaced the rear valve block and large accumulator; then the small rear accumulator, then the small front accumulator/pulsation dampener. At each stage I got the red ABC dash warning, and fluid overflow out of the top of the reservoir, mixed with periods of the ABC performing properly.
After I just replaced the last accumulator/ the pulsation dampener/ 2203270215, I waited 2-3 minutes, then fluid spewed out of the reservoir at high pressure. Then I got the red ABC dash warning, mixed with periods clearing DTCodes, of the ABC performing properly, then a couple of minutes after I turned off the engine, fluid overflow out of the top of the reservoir, and red ABC warning, repeat.
I have ended up with DTC: C1525-64 Stored&Current System pressure too low after the following code recently cleared: C1526-16 Stored&Current Malfunction in pressure supply. The fluid level is low, but the ABC functioned properly periodically a few times after I recently cleared codes.
Since I replaced or rebuilt the usual culprits, the only likely suspect for reservoir overflow I can think of is the 2203270231 = pressure relief valve behind left front wheel, which the pulsation dampener accumulator/ 2203270215 screws into. Should I replace the pressure relief valve next?
yes = 191 bar, see:---------------------1 of 2 Frame--------------------- 402 B4/5 (ABC pressure sensor) 191 bar ---------------------1 of 7 Frame--------------------- 175 Wake-up process OFF
However, I may need to do it when the red ABC message is active.
I just started the car, found pressure about 180, no red abc warning, cycled car up and down, got red warning, cleared codes, pressure kept going down, repeat, gradually pressure reading sank to 77 bar. I wonder if the pressure relief valve is sticking or has old bad internal seals. Anyone got this experience?????
I waited 2-3 minutes, then fluid spewed out of the reservoir at high pressure...
There are only two places fluid is stored under pressure: the struts and the accumulators.
For the struts to be the source of the high pressure leak, one or more of the blocking valves must have been forced open and you'd see that corner drop immediately, so that's not likely.
That leaves the two big gas cells (4 and 14) whose only path back to the tank is though the valve 52b so I'd definitely suspect that.
Looks like there is over-pressure (safety?) release valve parallel to 52b. Perhaps that is intermittently leaking both ways. Might be time for a complete "new" valve unit.
Search Ebay for "Mercedes valve block"; I see several clean looking ones for $80.
I just sprayed high pressure soapy water from a wand at a self service car wash onto the ABC pump, reservoir, and wiring to get mine to behave. I think hydraulic fluid was shorting an electrical connector. I had pressurized the hydraulic fluid reservoir with too much air pressure and sprayed hydraulic fluid everywhere. I had tried new valves, accumulators and pressure relief valve first.
Hydraulic fluid by itself does not conduct electricity. Automatic transmission fluid, PS fluid, ABC fluid and such are all just hydraulic fluid with small amounts of different additives and color dyes. Therefore, I doubt that ABC fluid conducts electricity. For sure automatic transmission fluid does not conduct as it coats all the electrical connections inside. From other forums I know that people in a pinch have successfully used e.g. John Deere tractor hydraulic fluid in their transmissions and PS systems with little if any noticeable difference.
Did you replace the accumulators with new parts? What is the fluid level with engine running? Overflow at the reservoir is usually caused by air in the system. This can be nitrogen from accumulators or possibly the pump sucking air.
Thanks guys. Unfortunately pressure washing the electrical connector after I tightened the return line nut on top of the reservoir, pressurized the reservoir, filled up reservoir, installed: used pressure relief valve, 4 new accumulators, 2 rebuilt valve blocks; cleared ABC low pressure and malfunction DTCs, had recurring reservoir overflows, had periods of working properly, then not working, periods of 190 barr pressure, then 1 barr pressure… only lasted a couple of days. Now it is back to red ABC dash warning and little or no (1-4 barr) hydraulic fluid pressure. Since pressure is supposed to be about 190 barr, HAS THE PUMP FAILED?
Mike - since there is negligible or no pressure, the fluid level is overfull on the dipstick all of the time - engine running or not. I filled it to normal running level when it was running earlier. When I pressurized the system fluid came out of the return line nut on top of the reservoir (and the dipstick cap during overflow). I used some huge channel locks to tighten the nut more than just finger tight. So, could the pump have sucked air there? I never bled a hydraulic hose. I think I never let the fluid get empty. How does air get into the system? My Diaglink Autel code reader shows the Wake-up Process OFF. Can I use my $20k retail ($500 on ebay used) Mercedes STAR DAS system to wake-up the ABC pump? Is that the same thing as pressurizing the reservoir? I pressurized the system already a couple of times, and had the ABC to work right for a while then drop to basically zero barr pressure. So, is the pump failing until it dies? Is it worth it to pressurize once again; or just buy a rebuilt pump now?
There shouldn't be much back pressure to cause that return leak. I would replace the filter and try priming the pump. If it builds pressure, try a rodeo to work all of the air out of the system. If if repeatedly loses pressure and pauses rodeo, you might need to replace the pump.
Thanks Mike… good to know about back pressure. One of the first things I did earlier was replace the filter and fluid.
When I started the car to get started with my DAS/ STAR/ XENTRY system, the ABC operated perfectly/changed from red overnight. With DAS I saw Wake-up Process ON, continued with f2 or f3 key, and it went to OFF. I cannot toggle it back ON… no worries, the pump works. I found a low pressure DTC, erased code. I found a dynamic test, ran that and it turned out to be the rodeo test. I fooled around a little with leveling the suspension. But corners remained a few millimeters different in heights.
I’ll head out to lunch and shop. If it misbehaves again, I will let you know.
When I went to lunch the red warning came on. By the time I fetched my diaglink and checked live data the pressure was rising from about 170 barr toward 190 barr. I erased the low pressure DTC and had no more red warnings for the rest of the day.
Before blaming the pump, I would personally first replace the valve block with the pressure regulator and over-pressure bypass. One reason is that IMHO a sticking over-pressure valve could give you the exact symptoms you have.
Also its only $80 and reasonably easy to replace. On the other hand a pump costs $700+ to have rebuilt and is a ***** to remove/install. Just my opinion.
The pump will usually start to leak and make quite a bit of noise when it gets old and loses pressure.
Replacing the pump on the V8 is not too difficult.
Thank you so much everyone. Mrvedit: Is the 2203200051 valve with attached sensor the one you are talking about? See photo below. This is plumbed into the front valve block and accumulator assembly. Tom, that is good to hear that the pump leaks and or gets noisy when it is failing. So, it is probably not the pump. Mike I ran the rodeo to remove any residual air in the system. I also ran the Wake-up Process, I think. I hope the later red warning that went away after I cleared the low pressure DTC was a last hiccup. The ABC system has worked perfectly since then with multiple drives done. It worked fine this morning… fingers crossed
I also included a photo of part of this Travertine Beige Metallic 500SL. It kinda’ looks gold. I like it.
Since I replaced or rebuilt the usual culprits, the only likely suspect for reservoir overflow I can think of is the 2203270231 = pressure relief valve behind left front wheel, which the pulsation dampener accumulator/ 2203270215 screws into. Should I replace the pressure relief valve next?
Thanks mrvedit. That is the pressure relief valve I too suspected. It is in the title of the thread. I did not specify 2203270231 again later in the thread. See the quote above from the initial thread post. I replaced the 2203270231 = pressure relief valve behind left front wheel, which the pulsation dampener accumulator/ 2203270215 screws into somewhere about 2/3rds of the way through this post. Afterwards fluid blew out of the reservoir after I filled the reservoir and turned off the engine. I then got the red dash light that only went away temporarily when I cleared the low pressure DTC several times. I think I introduced air into the system when I replaced the pressure relief valve, 4 accumulators, and 2 rebuilt valve blocks. and pressurized the reservoir a couple of times. I think I only got all of the air out of the system when I did the rodeo, and did the Wake-up process with DAS. I have my fingers crossed that it will continue to work properly now.
Sorry that I misunderstood that you already replaced the entire 2203270231. So, replacing this valve-body component made no change to your problem of fluid coming out of the reservoir and/or get the Red ABC message?
If true, they I am at wits end and can only hope that a more experienced person can help you.
Sorry that I misunderstood that you already replaced the entire 2203270231. So, replacing this valve-body component made no change to your problem of fluid coming out of the reservoir and/or get the Red ABC message?
If true, they I am at wits end and can only hope that a more experienced person can help you.
Au contraire mon amis. Thank you for your great analysis. I just started the car to verify that we indeed solved the problem without spending a small fortune. Everyone who helped when I asked for help contributed. Drop the mike. We are done.
UPDATE: While driving, I kept getting the red dash warning too low. My Diaglink would clear codes; and they kept coming back. So, I hooked up my old DAS scanner equipment. I got c1526-64 Sys. Pressure Too Low; and C1526-16 Malfunction In Pressure Supply. IIRC, I used F3 to run tests after the fault codes. It indicated that my pressure was about 50 when pressure should have been closer to 190 barr. It ran tests on the valve blocks for leaks, etc. then concluded that my pump was faulty. At some point I cleared all codes, and topped off fluid maybe ¼ inch too high on the dipstick. I turned off the engine; and after a few minutes, fluid burped out of the dipstick hole. IIRC I found the dynamic test again under actuations. DAS told me to keep RPMs at 3000. So, I ran the rodeo this time keeping my foot on the gas to over 3000 RPMs. As it ran the rodeo, DAS displayed pressures around 190 barr. After the rodeo my codes stayed clear, and I had no red dash warning. There was a big pool of fluid beneath the car. The dipstick showed fluid level normal. TA DA!!!!!!!!!!!!!
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Can pressure relief valve cause hydraulic fluid reservoir to overflow/spit out fluid?
