Bills600

I know this forums has many ABC-related posts, but I haven’t seen a post that matches my experience.

I am getting a red ABC - Drive Carefully mssg intermittently. It seems fine once the car sits overnight, t can drive it 5 miles or 200. If I dare stop somewhere for 30 minutes or so, I am guaranteed the ABC warning upon restart. Sometimes it can be extinguished by turning the car off and restarting it, other times I can’t. Regardless, once it sits overnight again there’s no malfunction.

I’ve checked the fluid level and it seems fine.

Any ideas what’s going on?

WTFauto

This is surely exactly what the diagnostic system is for. Hopefully it has actually logged a fault code telling you why, you just need to choose your poison in terms of connecting in and seeing what it is... somewhere between a diagnostic tool, and a dealership visit. With a car this complex, expensive to repair and old, it would be a sound investment to buy one of the STAR diagnostic computers getting around?

Sorry for not actually being able to give you a useful diagnosis.

tusabes

You’ll need star SDS computer to diagnose

Kebowers47

Intermittent ABC warning (amber, not RED) It seems apparent the problem is a heat-related malfunction of some electrical/electronic components. IMHO,
Step 1 is checking the oil level of the ABC reservoir when the engine is running.
2 is a difficult and time-consuming search. and-test of ALL the wiring connections--any one of the dozens could be the cause. If wires and connectors are loose and flopping around, they can move into extremely hot zones. Add heat shielding/insulation to any wiring and components from hot air and RADIANT HEAT from exhaust components.
3) Try raising and lowering the car several times with the dashboard switch. Sometimes the height sensors will get 'lazy' in a particular spot and simply 'exercising' them fixes it.

Mercedes licensed the technology from Nissan and did their own implementation with a much small set of functions and capability. There may be restrictions on just how much information Mercedes can disclose to 'outsiders' like vehicle Owners' who are not restricted.by the License terms

tusabes

There is no such thing as an amber warning
it’s either white or red

Bills600

Thanks to all who’ve responded to my post.

Drove the car today into town to pick something up. As expected, after stopping at the store, as soon as I started the car I had the ABC light. After about 1/2 mile while at a stop sign I turned the engine off and immediately restarted it. The light cleared and did not return for the rest of the ride home. I should be picking my Saab up at my local mechanic in a few days and will ask him to scan for codes to see what he finds. I’ll repost once I have more information.

Kebowers47

The intermittent ABC 'be careful' warning begins to act like a defective 'high oil temperature' sensor /connection is causing the problem. I do not think any 'hard part' would act tike you describe.

Bills600

Finally made it to my local mechanic on Friday and asked him to read the code. SDS suggests it's a low-pump pressure issue. Since the pump is clearly working - the car rides as normal, and won't trigger the light on the initial start - he suggested that the pressure may drop out of range once the fluid heats up. I'm weighing whether I want to go for the cost of a pump or continue to drive it as is - as it appears the system works but the pressure is low. He said he could tell me how much pressure the pump was putting out, but I didn't ask him to go back out and do it since it was raining very hard (In hindsight I recognize this would have been valuable information). The light was on when I got home, but of course in the morning drove the car for over an hour with no light on the initial start. Does this make sense?

tusabes

There is no guarantee a new pump will fix a low pressure issue , this guy tried three pumps with same result of pressure drop when . Fluid heats up

https://www.benzworld.org/threads/ab...#post-18091341

as long as your system works I wouldn’t worry about the error message

Astro14

Since the warning happens with hot fluid, and fluid viscosity drops with a rise in temperature, I would flush the fluid. Change all of it. New fluid will have a higher viscosity than worn out old fluid.

Best way to do that: disconnect the fluid return line and put it in a graduated 5 gal bucket. Remove the fluid from the reservoir, and fill with fresh fluid. Have several 5L jugs of fluid* available. I used a 2 gallon pressure fill container filled with CHF-11s. Start the engine and begin a rodeo with SDS. Keep the reservoir full with fresh fluid. DO NOT let the pump run dry or suck air. When the fluid running into your graduated waste bucket is clear and green, you've replaced all of it. You can shut down the engine and stop the rodeo.


*CHF-11s, available on Amazon or RockAuto for about $75/5L jug.

Bills600

Thanks for the responses. Had the car out again today - same pattern. I thought about changing the fluid, but I had the car in the shop a couple of months ago and all of the fluid was replaced (the motor mounts failed and crushed the line over the transmission - had the line replaced, new mounts, and fluid replaced). When I check the fluid level it looks good (green), but on the dipstick the fluid is foamy - which makes me think air is getting into the system somehow. I have not noticed any fluid leaks and the measurement via dipstick looks consistent. Considering the pressure of the system, if air gets in I would think fluid comes out. I know I can probably drive it as is - but my wife hates getting into the car because she's convinced we are going to get stranded every time she sees the ABC light. Based on the fact the fluid is new - would you still recommend I have the fluid flushed?

Astro14

In that case...I wouldn't bother...I'm back to the pump, then, but that's a very expensive guess on my part.

ItalianJoe1

Air could be entering the feed line into the pump. I've seen that exact thing happen and it caused me hell to diagnose, the system would be fine when cold, and if I carefully bled it it would be great. As it ran longer and longer, it got more and more aerated and noisier. Turned out the hose leading into the pump had a hairline crack right near the clamp, no pressure inside so it wouldn't leak, but was drawing air when running and had suction inside.

Bills600

ItalianJoe1 - interesting. How did you diagnose? Is the feed line the one that runs over the transmission (and was the one recently replaced)?
Astro14 - my mechanic said he can pull/replace the pump (labor only) for under $1K. He suggested the pump could be rebuilt (Mavel) though clearly that's at my risk. I'm sure he'd prefer that if I did the pump it would be new/OEM, but he's trying to work with me considering the age and value of the car (which I greatly appreciate!). Any experience with rebuilt pumps?

tusabes

It’s not your pump . Don’t replace it

Astro14

My experience with rebuilt pumps is spotty. I bought one, didn't get around to the install for several months, saw a flaw on the output fitting, too late to return, so I put it in a box and bought a new MB pump from the dealer. They gave me a good break on the price, but it was still about $1,200. The MB pump works great. That was all about a year ago. I kept the rebuilt pump as a core/spare for future contingencies.

But spending over $2K on a hunch is an awfully expensive way to proceed. I hadn't heard of a feed hose flaw, but it's worth checking a bit more to be certain of the diagnosis.

Bills600

tusabes - I know you suggested I just drive it as is... but I'd really like to eliminate the warning light without haphazardly throwing parts (and $$$) at it. If not the pump, where would you start and how would you diagnose?

tusabes

You have a fluid viscosity problem not a pump problem

either air is getting in the system affecting viscosity by foaming the fluid or the fluid itself is getting too thin when hot .

ItalianJoe1

The line from the reservoir to the pump, it's just regular rubber hose, it carries no pressure. The car I had the issue on, I put a vacuum bleeder on the reservoir and was unable to hold a vacuum, which made me search for a leak. Once I lightly pressurized the reservoir, I got fluid coming down near the pump, and found the hose split. The car in question had had a pump replacement done recently so I'm sure the brittle hose just split on install and was either missed or ignored, but it was causing fluid aeration during operation similar to your issue.

Bills600

Sorry for the delay in keeping this post active. I've been doing some work on my corvettes when time permits, and driving the 600 with the ABC light on. As per my previous posts it is incredibly consistent - no error when driving it cold, regardless of distance. Once I turn the engine off and restart it, I'll get the ABC light.

Perhaps it's my imagination, but there seems to be a change in the system performance consistent with the error mssg. It seems to ride better on the cold start - even on a 3-hour trip. Once I restart it and the light appears, it seems to be a bit bouncy. Not tuna-boat bouncy (I've experienced this before), but I do sense a reduction in ride quality.

Perhaps I'm looking for something that isn't there. Does this make sense?

tusabes

Have you pressurized the reservoir and checked for leaks as suggested above ?


have you replaced ALL four of the accumulators and pulsation damper in the past?

if not I would Replace them it’s part of normal maintenance , it’s not throwing parts at it because they are regular wear items and most people do not change all four

Bills600

After my last post I decided to drive it as is and ignore the warning light. Started to develop a loud noise in the front end when turning or coming up the driveway apron. As expected the car needs ball joints/control arms, which my mechanic is doing. While he had the car I asked him to take a look at the ABC issue I’ve been having. He told me one of the valve blocks is shot. When the car rests the fluid is rushing back into the reservoir and the car is dropping slightly (not enough that it is noticeable). This is also causing the fluid to foam. We discussed the pros and cons of replacing the valve block - the cons being the cost ($2k for the part alone) and the fact that one of the other valve blocks can go at any time. He also said he’s rebuilt 3 or 4 of them without any success - they tend to fail immediately or after a short period of time. After some discussion, I told him to do the front end work and I’ll continue to drive it with the valve block the way it is. If the situation deteriorates I might reconsider.

Make sense?

Astro14

There are only two valve blocks. One front. One rear.

New ones cost about $1,800 but have upgraded solenoid valves.

However, taking them out isn’t hard. For about $12 in orings (at a shop) or a $50 kit on eBay, you can clean them up and fix this leak.

That may solve your low pressure issue as well, if they’re letting fluid past when they shouldn’t.

I did mine about four or five years ago. Still says at proper ride height then parked for weeks.

You’ll need a good 17mm line (flare nut) wrench. German, like Stahlwille, or USA, like Proto, Wright, Williams, or Snap On, no cheap junk from Harbor Freight.

Bills600

Thanks. My mechanic’s experience has been that rebuilding them hasn’t been the way to go. He said he’d do it, but didn’t recommend it and felt I’d be back unhappy with the same issue before long.

I’m not sure I would do this myself... but maybe. I will look for a DIY to see how involved it is. I can probably remove and replace, but would worry about getting air or foreign matter into the system (working without a lift) and causing other issues. If I could keep the fluid in the system that would be a real bonus.

I also found this link (see below). Anyone have experience buying from them?

https://www.abcspecialist.nl/en/arti...-mercedes-benz

tusabes

There is a guy on eBay who rebuilds then for $139 , much better then trying to rebuild yourself if you aren’t skilled his eBay name is vtrading916