R230 - ABC Fluid level very low while engine running

[koopz]

Just before Christmas I got the dreaded red ABC warning. Suspension went very floaty and the button to raise and lower stopped working. Got the car home and plugged it into SDS and had System Pressure Too Low and Malfunction in Pressure Supply faults. Pressure was reading around 110-115 bar (I believe it should be about 180). Checked the fluid level and it was low, so I ordered some fluid and waited. Got it topped up yesterday morning to the correct level and straight away the warnings went away and the button to raise the suspension was working again. Checked the level again this morning and it's still in the same place, so if it is leaking somewhere it's not a catastrophic leak. I haven't checked the pressure reading yet, and the car is not currently being driven.

The thing that is really confusing me though is that when I check the fluid level on the dipstick with the engine off, it's in the right place (on the high mark). But when the engine is running it's way too low - right at the bottom of the dipstick. Turn the engine off and wait for half hour before measuring again - back to the high mark. Where could the fluid be going while the engine is running? Has anyone experienced this before?

 

[ToeKnee]

Could you have a weak pulsation damper and when the system is under pressure the pump is filling the damper so low fluid but when off the damper is pushing the fluid back into the reservoir showing correct level?

 

[koopz]

Possibly. On another forum it was suggested it could be accumulator related, but someone said its the wrong symptoms. Just wondered if anyone had seen this same issue! I think it's probably worth changing all the accumulators anyway as the car is on 64k miles and I doubt it's ever been done. The fluid has been at a constant level with the engine off so it doesn't seem to be leaking. I suppose the fluid must be going somewhere inside the system

 

[swithin]

Got abc malfunction on my R230 the other day. Filled reservoir which was a bit low and it hasn’t come on again. The day before it gave the warning, engine noise in the cabin all of a sudden became louder at lower speeds. After topping up the reservoir the noise went away for 5 mins then came back. Been quoted £1,500 for the repair . Cars only done 46000 miles but is 15 years old.

 

[Dickster]

There are two marks on the dipstick, one for a running motor and one for when it’s switched off.

At 60k miles I would change the front and rear accumulators and pulsation damper.

 

[BaldGuy]

Got abc malfunction on my R230 the other day. Filled reservoir which was a bit low and it hasn’t come on again. The day before it gave the warning, engine noise in the cabin all of a sudden became louder at lower speeds. After topping up the reservoir the noise went away for 5 mins then came back. Been quoted £1,500 for the repair . Cars only done 46000 miles but is 15 years old.

That'll more than likely be the Tandem ABC/Power Steering pump that needs replacing...

 

[koopz]

There are two marks on the dipstick, one for a running motor and one for when it’s switched off.

At 60k miles I would change the front and rear accumulators and pulsation damper.

Yeah, with the engine off its at the right mark, with the engine running it's at the bottom of the dipstick nowhere near either of them

 

[koopz]

So I took the car out this morning for a 10 minute drive to the shop and back, checked fluid level with engine off first - at the correct level. After about 2 mins driving I got the white ABC fault, couple more minutes the red one. Carried on to the shop, on the drive home I got the white ABC error, no red one this time. Checked the fluid with the engine on and it was right at the bottom of the dipstick, but I noticed there were bubbles on it. Checked again a couple more times and the level was actually rising up closer to the lower mark, still lots of bubbles. Just went out and checked after letting it sit for half hour with the engine off, and it's about a cm below the top "engine off" mark - so unless that's been caused by me sticking the dipstick in and out it's lost some fluid. I'm going to top it up to the correct mark again and keep an eye on the level

 

[koopz]

Thought I'd post an update for anyone else having similar issues.

Decided to do the front first and see how it goes, so I ordered an accumulator and pulsation damper direct from Mercedes. It was the same price as what I could find elsewhere so made sense to go direct. Also ordered a new front wheel arch liner and undertray and they were actually cheaper from Mercedes than elsewhere - just shows it's always worth asking for a price from Merc first! Over the weekend I swapped them out - actually a pretty simple job. The accumulator was easy to get to with the front wheel arch liner and front bumper tray removed, and the pulsation damper is even easier. If you remove the side "vent" cover, it's right there. I didn't even need access from behind the wheel. It was on very tight so I soaked it in WD40 overnight and the next day it came off just fine.
Put everything back together, topped up the ABC fluid and took her out for a 30 mile drive, good mix of motorways and back roads, lots of bumps. No errors! So it definitely looks like the accumulators were the issue. The fluid in the reservoir is still low when the engine is running, but not as low as before - I'm guessing once I get the rears changed as well it will be back to normal.
So next job is to change the rear accumulators, and then I need to sort out the leaky boot.

 

[alabbasi]

Accumulator may have blown which would let more fluid in. Replace them all. They all go in at the same time so expect them all to fail at the same time

 

[koopz]

That's what it looks like. Changing the rears is next on the list

 

[Dickster]

Well done. You can tell when they’ve failed, just try dropping a thin screwdriver in the hole. If it’s ok it won’t go in far because the diaphragm is in tact.