This is a picture of the car.

 

Would also know the location of the abc ecu. I wanted to check the conditions of the pins and connector.

 

The ABC control module is under the dash, driver's side, sitting horizontally above the steering column:

http://benzbits.com/r230/ABCControlUnit.pdf

 

No doubt you had basically no hydraulic pressure. Star Diagnosis directs you to replace the pump, but before doing that I would post this over on Peachparts.com's Tech Help forum. A dealer Tech that goes by username ILUVMILS has experience with ABC, and he hopefully he will reply to your thread with something constructive.

The pump is a simple mechanical device consisting of 7 pistons in a radial arrangement. As stated before, I do not understand how the pump can develop enough pressure to run a Rodeo in one instance and later have no pressure.

 

I has similar problems last summer.. Out of nowhere I got the red "visit workshop" message and the valves shut (in good height so I was able to drive a few hundred meters back to the garage). Then did a number of tests getting 1-2bar pressure all the time.

Let the car sit for the night and strangely it seemed ok again.. did rodeo (with less pressure than yours.. between 85-90 to 140 during the test..). Then red message again.. restart - working.. on an off like ten times and 50% red message and no pressure the rest working fine.

I removed the pump and dismantled it. One of the bolts holding the pistons seemed to have "undone" itself perhaps one turn (the others bolts felt the same but this one was definitely not tightened as much - the first I unscrewed of course and with nothing to compare with I didn't really notice at first but after feeling the power needed to unscrew the rest it was obvious.. not enough torque or to little loctite- looked like there were more "glue" on the other bolts).

Anyway.. did a lot of reading and while looking for placement parts for pump (seals etc) I checked the suction restrictor valve (sits on the pump - 0-5v valve regulating how much pentosine the goes into suction side of pump)... it was "sticky" as hell.. did a thorough cleaning of it which really took time.. used a 5v power supply to open and close it like a thousand times in different solvents to get it clean.

Then got a rebuilt pump, new main pressure line to first valve block (hose sweating oil), all four accumulators was replaced and everything put back together. Car feels like new in the chassi again - have done more than 2000km since this repair (that took like five weeks at home in the garage with "standard tools")

I think that the suction restrictor valve was the culprit but the pump would probable have failed soon enough as well as the main pressure line so it feels good to have done this now..

Summary; remove the valve and test it with 5v.. it should open instant and "exact".. this part is normally not included in the cheaper rebuilt pumps and that was why I started testing it.. also I got a feeling that many pump failures is due to this valve and probably also as many due to piston bolts coming loose which could explain the number of failures with metals shears in the system - the bearings seems ok after 12300km and everything inside the pump looked like new..

 

First off all many thanks to bobterry99 for all the patience and help.


Secondly perren, it was very interesting to hear your story, maybe I could pull the suction valve and clean it. Is it easy to pull, without taking the pump out ?
How would I apply 5v when it is out, I only have a 12v battery lying about ?
Did the suction valve have o rings ?

 

Unfortunately I don't have any pictures of it lying around but I googled it and got
A good match at benzworld...

http://i74.photobucket.com/albums/i2...rs/ABC/017.jpg

It's the part in the centre of the linked pic.. just below the centre of the picture with a cable connected to it..
as I remember it it was very easy to access if you remove the abc fluid tank and hoses.. might be possible to access even with those parts still in place - it's on top of the pump..

Maby you could use 3-4 small 1,5 volt batteries in series to give it a go.. I don't think 4,5 or 6 volt matters but the coil in the valve probably won't like 12v in the long run - and also - when I tested mine I did test with 12v power supply with 0,5A capacity (dropped to around 8v when connected) and with that power it opened much faster than with just 5v so I doesn't give a good view of the function of the valve... I also - after cleaning - tested with 1, 2 and 3 1,5 v aa batteries to check how it worked and got the feeling that it was ok..

 

Star Diagnosis can actuate the valve with the engine running. Perhaps it can do it with the engine off as well. Note that the resistance of the coil is only a few ohms, so if you are going to connect a battery I would use a 6-volt lantern battery.

There are two o-rings: one internal, one external.

One thing to know about the restrictor valve is that while the engine is idling the valve is in its closed position to minimize the supply of fluid to the pump. Therefore, if it is sticking and affecting pressure it is going to cause the pressure to be high -- not low. Still, inspecting the valve may be worthwhile.

In the valve's closed position a small amount of fluid is still allowed to pass through small holes that you can plainly see. You might try to blow air through the valve to verify that the passageway through those holes is clear.

 

Mine was sticking in closed so I recon that the system would "work" when no load is applied on the suspension but when more "power" is needed and the valve has trouble opening there will be a pressure drop error code as the pump doesn't get enough feed of fluid. In my case - that in addition to a pump being weak due to bolts unwinding it was probably the cause of my problems..

I've done a fair bit of research on how the system works and feel quite comfortable about it now even though there are a lot of things that could fail.. but compared to the feeling when the car runs great I guess I could live with it

 

A valve that is stuck closed functions correctly while the engine is idling. With a simple test the OP can satisfy himself that a sticking restrictor valve is not his problem.

Connect to the ABC controller with Star Diagnosis and monitor the ABC pressure. Start the engine and observe proper system pressure of 180 bar or so. Now simulate a restrictor valve that is stuck closed by removing the electrical connector at the valve. I expect that the system pressure would remain unchanged.

 

I will try this test too. I don't understand that when you start the car, why would you expect to see a pressure difference if there is a fault ?

 

If the restrictor valve is required to open for the system to have pressure at idle, then a valve that is stuck closed will cause the pressure to be low. But it is my contention that at idle the valve is supposed to be closed anyway, so if it is stuck closed there will be no consequence at idle.

Here is a test that may not help prove anything but could be interesting. At a time when you have 1 or 2 bar of pressure use Star Diagnosis to open the restrictor valve. Observe the current through the valve and the effect on the pressure.

 

OP you appear to be UK based so i recommend you also post on............

http://forums.mercedesclub.org.uk/index.php

There are a few ABC experienced members on the forum. Bobterry99 is doing a great job here as well.

 

Here is a strange thing. My normal journey first thing in the morning is 2 miles (car working perfectly fine). I stop off for 5 mins and jump in car, the white ABC warning light pops on, followed a few seconds by red warning.
Yesterday my journey was different. First thing in the morning I drove 6 miles, no issues. I briefly stopped off for 10 mins and the white ABC light came on, but no red warning until a further 2 miles.

This morning everything was back to normal, drove 2 miles Stopped and restarted, red warning popped up.

I have come come to the conclusion this is possessed by a poltergeist.

 

Ok so I did the test. Please see pictures. What is going on ?

 

The last picture above is with engine off, I think

 

If the engine was off, then evidently the software ignores user input and will not open the strictor valve unless the engine is running. Therefore, if you want to remove the valve and check its operation you will have to power it with a battery or some other external source.

With the engine running and the strictor valve energized hydraulic pressure did not increase and remained at zero. Had it increased you could have concluded that at idle no fluid is flowing through the closed strictor valve and its small passageways are blocked; but since pressure remained constant nothing is learned.

It still seems that you implausibly have a faulty pump that is binary in performance and makes good pressure at one moment and no pressure at another.

 

I think I read on one of the forums somewhere, that some pumps worked sometimes. I wonder if the fault is actually inside the pump has perren75 said, that is making the pump erratic. Something cuts the pressure off, then reinstates it when left for about 4-5 hours.


Could the system be sucking in air when started, then the air expels when the car is left to rest ?


Could it be that when the car warms up, something expands and starts to stick.?


Does anyone know a good preist!

 

Do you think a fluid and filter flush may solve the problem ?

 

Have you perhaps noticed "bubbles" in the oil reservoir? Has the fluid level been low? Bubbles might be due to a bursted accumulator and perhaps they could be sucked in by the pump even if this feels very far fetched... (as a theory of the possibility of air in the pump)...

When installing a new pump it's a good idea to "prime" before starting the engine to get rid of all air in the pump. I did this by opening the valve (external power to the valve and manually turning the pump until it was filled with oil.. during my rather extensive research on ABC when I had the failure last year my conclusion was that the pump cannot bleed the air on itself - it needs to be bled..

Based on the rather high pressure reading you get from time to time it still seems to build enough pressure so I think it's odd if the pump is "game over".. that's why I suggested the valve. I've read about failing valves in several different forums..

But.. I'm no expert on the system and rest my case.. just thought it would be a good idea to have the valve checked in order to rule out a simple thing before removing the pump.. (I would have done that if I'd read about valves before removing the pump.. but with one bolt on its way I'm lucky I replaced the pump.. also my pressure was below 90bar short moments during rodeo so the pressure was not good enough anyway)

There are seals, springs and other parts that might fail inside the pump but if the fluid is in good condition I think the pump should be good to go for very long. It's no rocket science - more "simple mechanics " in my opinion.. my pump looked very good inside - no rust (or at least brown colour) as I've seen on some pictures..

 

I am going to pick up a lantern battery today from Wilkinsons, and have a go at removing the valve, the car has been parked up all day, so should be depressurised. I'll test the valve to see if it moves smoothly with 5v, and give it a good clean, and see what happens.

 

Tried to remove valve. It is almost impossible to get to the bolts properly without removing the pump. Also I felt that the bolts were weird. Non of my tools would fit properly. The best fit I got was a Alan key socket and that felt lose.
Ive been told you cannot buy a restrictor valve on its own anyway. Even if it was the valve I would have to buy another pump. I am going to buy a remanufactured pump and try that. May have a look at the restrictor valve when the pump is out.

 

With regards to suction valve test on STAR. My apologies, you can actuate the valve without the engine running. Here is a picture without engine running.

 

Regarding the suction restrictor valve with engine running, without red warning

 

Here is the funny thing. I then performed a rodeo and about 5 mins into it the pressure dropped gradually to 50 bar and the car stopped moving.
I immediatley went back to STAR to check the suction restrictor valve again. See pictures