SL55 ABC mind of its own!

[F1BHP]

What does the, cut the ears off the heater box drain do?

 

[television]

What does the, cut the ears off the heater box drain do?

Stops water from going down into the inner sills and screwing up the whole wake up and CAN system.

 

[F1BHP]

I assume they fixed this problem on the facelift. Or not?

 

[television]

I assume they fixed this problem on the facelift. Or not?

Nope, nothing has changed, just 1 leaf falling down will block it. I must do mine in the spring.

 

[Philedge]

exactly what i thought i was trying to say smooth roads smooth driving , no demand ,oil reaching valve block returning thru filter back to tank. demand seen ,pump unrestricted ,more flow , more oil returning to tank thru filter now back to these pumps. if eccentric, when there is little or no demand (load) the vanes tend to chatter a bit around the eccentric ring creating uneven and more wear . than when they are loaded . thus perhaps providing some explaination to issues of wear on this system, high miles v low miles failures, as i believe a pump on a car driven reasonably hard on less than perfect roads will probrably last longer than the same pump on a car poodling about on great roads. just my belief .

Thats almost how things are set up, but......

Google "r230 hydraulic schematic" and look at what should be the first image found which is a schematic of all the piping and hydraulic components.

Your scenario of driving on a smooth road with no acceleration/deceleration/ cornering is the same as having the car sat still with the engine running ie theres no hydraulic demand on the system. In this case once the system is pressurised and the valve accumulators are charged, the pump is throttled by Y85/1 and the limited flow of oil is routed through pressure regulator 52b and then returned to the reservoir via the oil cooler and filter, 9 and 2a. It doesnt flow to or from the valves as there is no demand from the valves.

As soon as you accelerate, brake, corner or hit undulations in the road there is fluid demand to load or unload one or more struts. As soon as the first valve is opened fluid is drawn from the valves accumulator and the pressurised pipework. I dont know exactly what triggers the pump throttle valve to fully open but it may be as soon as the ECU is about to open a valve or when the system pressure starts to drop. Either way the pump goes to full flow to maintain pressure. If there is still fluid demand but the ssystem pressure is reached then the pressure control valve 52b will regulate the pressure around 200bar.

If the coil spring in the strut needs to be loaded its valve is energised positively( I think)and a shot of presurised fluid goes into the strut as required to correct roll, squat, dive, bumps. If the spring needs to be unloaded then its valve is energised negatively to vent a shot of fluid from the strut into the low pressure return pipework. This fluid is returned to the reservoir via the oil cooler and the filter.

Hopefully that explains how all the fluid in the system, except for the stagnant stuff in the struts, circulates continuously through the filter.

According to the schematic diagram the pump is a radial piston pump. Does that make a difference to longevity over an eccentric one??

 

[Philedge]

Absolutely, as I have said before, the problems that most often come up are one corner sinking, the rear end raising when in R. this is another reason why the wheels must be hanging down when bleeding to empty the struts as far as possible.

I'm sure we've discussed contents of struts before and eventually agreed that the struts would be empty in the compressed state rather than uncompressed with the wheels hanging down?

The rationale for this is that if a valve block is leaking or a pipe bursts the strut will collapse as it ejects most of the fluid inside it either back ti the reservoir or onto the road.

 

[television]

I'm sure we've discussed contents of struts before and eventually agreed that the struts would be empty in the compressed state rather than uncompressed with the wheels hanging down?

The rationale for this is that if a valve block is leaking or a pipe bursts the strut will collapse as it ejects most of the fluid inside it either back ti the reservoir or onto the road.

The correct procedure is if changing the fluid. let the car stand on its wheels and empty via bleed screws. do up bleed screws and fill system, while watching the fluid level start engine and keep it topped up. Turn off engine and correct fluid level once the 2 leds have gone out. Start engine and raise and lower at least 20 times. (note that if a new pump is fitted, this should be pressure filled)

To bleed, lift car so that the 4 wheels are hanging down, while someone is watching and filling the tank, undo the bleed screws till all air is out. Close the bleed valves and correct fluid level.

 

[Philedge]

The first line above says to empty via the bleed screws with the car on its wheels so the struts will be compressed by the cars weight, not hanging.

 

[television]

The first line above says to empty via the bleed screws with the car on its wheels so the struts will be compressed by the cars weight, not hanging.

I am talking about bleeding with the wheels hanging, obviously you cannot empty the system with the wheels hanging, through the same reason as you cannot bleed the system with the car standing on its wheels.

 

[Philedge]

I really dont understand why the wheels have to be hanging to bleed them. Is this using STAR to override ECU function?

If the ABC is being controlled by the ECU then the ECU would see all 4 struts as being extended too far. Surely the ECU would operate the valves and vent fluid from the struts to try and get back to normal ride height? That being the case there would be no pressure at the bleed screws to bleed any air out?

 

[television]

If you undid the valves while standing on its wheels, the all the fluid would just be forced out. With the wheels hanging down and you bleed, it just sprays the fluid out in fits and starts, and you keep doing it till the flow is constant.

 

[Philedge]

I think I've worked out why things dont stack up for me! I've only ever talked about changing the fluid which doesnt introduce air into the system so no bleeding required and no hanging wheels.

Happy birthday by the way

 

[television]

I think I've worked out why things dont stack up for me! I've only ever talked about changing the fluid which doesnt introduce air into the system so no bleeding required and no hanging wheels.

Happy birthday by the way

Thank you,,,this is a complicated subject, but surely you must still bleed as there will be air in the pipes, unless you do not completely drain the whole thing and change the fluid that way.

 

[Philedge]

I dont know if there is an MB fluid change procedure, but when I asked MB Chester they didnt know about fluid changing!!

The DIY version that I have used and that is well documented on the web, is to remove the return pipe from the reservoir and route it to a bucket. This pumps the old oil out of the system while the engine is running and the suspension being repeatedly raised and lowered. At the same time add fresh fluid to the reservoir which fills the system with fresh fluid.

As the system isnt broken into no air enters so no bleeding is required.

 

[television]

But that will do nothing for the fluid or any air in the pipes, just the front loop.

 

[Philedge]

Theres no air in the pipes when you start the flush and you dont introduce any so long as you keep the reservoir topped up.

As all the struts are raising and lowering fresh fluid is routed to all 4 valves and part way into the pipes to the struts. All the old oil returned from the valves is dumped into the bucket.

 

[television]

But why not do it the correct way to make sure there is no air in the pipes, and change some more fluid from the pipes. We know that with the car sitting right down the struts are virtually empty.

 

[Philedge]

But why not do it the correct way to make sure there is no air in the pipes, and change some more fluid from the pipes. We know that with the car sitting right down the struts are virtually empty.

??? Theres no air to start with and no air gets introduced so no air in the pipes.

All the old fluid in the pipework gets flushed out by the new fluid entering the system. If you vent each strut and allow it to collapse then close the bleed nipple no air will enter( same as bleeding brakes).

 

[television]

??? Theres no air to start with and no air gets introduced so no air in the pipes. All the old fluid in the pipework gets flushed out by the new fluid entering the system.

Not if you do it with the return pipe as you said earlier, if I am going to the trouble of changing the fluid , then I would rather change as much as possible, that is emptied with the car right down.

The car may have had a new strut, or the valve block may have had problems, so again I would rather fill and vent by the book.

 

[Philedge]

Your quite right that the struts should be collapsed to get the old fluid out, but that doesnt introduce air. Just put a pipe over the nipple, crack the nipple and let the strut slowly collapse until its bottomed out and then close the nipple as you would when bleeding brakes. No air is introduced. You can then start the car and raise the suspension and the strut will be filled with fresh fluid. Repeat for the other 3 struts. Job done.

If you replace a strut then more extensive bleeding may be needed, but we're only talking about flushing.

When I removed and stripped my front valve block all I did to bleed it was start the engine and raise and lower a few times and the air gets carried out with the oil returning to the reservoir. I seem to remember when Alex changed his accumulators recently raising and lowering a few times got all the air out.