October 3

2003 Mercedes Benz SL500 – ABC suspension



Mark: Hi, it's Mark from Remarkable Speaking. I'm here with Bernie Pawlik, Pawlik Automotive in Vancouver. Vancouver's best auto service experience, and we're gonna talk cars. How you doing Bernie? 

Bernie: Doing very well. 

Mark: 2003 Mercedes Benz SL500 that had a suspension issue. What was going on with this relatively famous sports car?

Bernie: Yeah. So this vehicle has the active body control system, otherwise known as ABC. And it's the hydraulic suspension system, which I think what makes this car kind of neat. And it's not entirely unique to this model of Mercedes, but a few different models have it, but it's speaking from experience, because I own an SL55. It's a pretty awesome system. The car always sits level. You can raise it a little bit if you need extra ground clearance, God knows why. If it snows out, which is the worst car in the world to drive in the snow. But you can do it. 

But anyways, it basically adjusts the suspension. When you go around corners, the vehicle never leans, it just goes straight around the corner. When you hit the brakes, the car never dives. It's pretty awesome. So anyways what was happening with the vehicle is that the suspension would, would drop, like sometimes overnight the customer would leave it and he'd find the vehicle especially on the front, the car would be down. 

I'll just actually go straight to the screen share of the car right now. You can see the vehicle sits nice and level. You look at the distance between the top of the tires and the wheel well, they fit really nice. And this is the suspension on the lowest setting which is where you kind of wanna be driving it, for best sporty driving. The vehicle would actually drop. So you'd find this fender would be kind of over the tire too much. And the car would sit on an angle. 

2003 Mercedes Benz SL500 - ABC suspension

And by the way, just a little tip on this car, it's in the owner's manual, when you park the car, you're always supposed to put the wheels straight, because if there is a problem with the suspension dropping, the fenders will actually start resting on the wheels, which is obviously not something you want. So if you own a Mercedes that's an ABC, always park it with the wheels straight. Anyways, get back to us and we'll look at pictures some more. 

Mark: So, had you done any other work on this car previously? 

Bernie: Yeah, we did actually. We'd done a whole bunch of work on the suspension. He was a new client who came to us this summer. The car had a number of issues, included a dead battery, a whole bunch of things that weren't working. So we did a bit of work on the vehicle. A lot of maintenance work, fluid changes, that sort of thing.

But we did address some suspension issues with this actual same problem. So sometimes, you know, we bite these things off in bits and pieces. This is kind of the second round of repairs. So the first repairs I found the right front strut, suspension strut was leaking.

So that was the first thing we repaired. And then after that, actually I worked on the car myself, drove it and if you go over like some speed bumps pretty hard, there's a red warning light that would come on, you could feel the car kind of knocking and bumping. So there was something in the system that wasn't right.

It would set a low system pressure code, even though the pump itself was working fine. So from diagnosing that we replaced the accumulators. These were basically big diaphragms that hold pressure and they'll be able to release it very quickly because the suspension needs to adjust in fractions of seconds.

So the speed bumps were pretty good indicator. So we replaced the accumulators. And did that the car was great. Held pressure really nicely. Go over those speed bumps. No more warning lights, everything was good in that department. Left the car overnight for a couple of nights. It seemed like it was sitting fine. So customer took the vehicle and then after a day or two, it did the same thing again. It dropped, especially in the left front corner and he had a red warning light came on, so he was pretty concerned about it. So we rediagnosed it and figured the suspension valve blocks were the next thing to be repaired.

Mark: So you mentioned this is a hydraulic suspension. It's not an airbag suspension. 

Bernie: No, it's not air. It's got a pump that's driven by the, it's called a tandem pump. The power steering pump is actually two pumps. One of them does the power steering, the other section does the hydraulic pump.

And it'll go up to, I mean, it's like 3000 PSI or something like that. I don't have my numbers quite right, on the scan tool, it always reads in bar and it's 180 bar or something, it's a lot of pressure. And so it's got that plus a series of metal lines, I mean, these are like solid metal pipes that run all through the vehicle to each corner. It's got a valve block in the front, a valve block in the rear, its got accumulators, plus all the struts and its got level sensors and plunger sensors inside the struts. So there's a lot going on to make this work. It's not like a couple shocks in each corner. 

Mark: So really complicated. Why would the control valve cause the car to drop when the car was shut off. 

Bernie: I've never looked at the inside of them, but what I imagine them to be, these are very large solenoids. We're gonna look at pictures in a second. They're very large solenoids. They're valves that you know, they have seats and they hold pressure. There's a lot of pressure in the system, so they have to hold that pressure. So if there's a slightest bit of leakage, the car will start to drop and that's what's going on.

So the car is, it's a 2003. That's what, you know, 19 years old at this point, it's got a lot of time on it. As I say, in any car, if you keep it long enough, every part will fail. But if you have a car that's 50 years old, there might be some parts that still don't fail, but you just never know. Anything's a potential failure item.

2003 Mercedes Benz SL500 - ABC suspension

Let's just look at some pictures, the valve blocks. So there's the car again. Here's a shot of the valve block. This is the new replacement and this is the old one. Thing that's interesting, when you look at this old one is you notice, these are the solenoid there's basically a blocking valve and a control valve.

2003 Mercedes Benz SL500 - ABC suspension

So one will release pressure. One will actually block it. And I don't know entirely how they work inside. It's not really possible to disassemble 'em without smashing 'em apart with a hammer which is unfortunate, it'd be nice if you could actually take it apart and try to service it and clean it, but they didn't give that option. But you notice the solenoids look much larger on the new units, that's the one on the left. 

2003 Mercedes Benz SL500 - ABC suspension

This is a different view looking at the other side of it, but again you can see the solenoids, they're much larger than the original unit. So there was probably something that happened along the line where they made them a little bigger, maybe a little more reliable, although, you know, we don't replace them that often. They don't fail too often for actual electrical issues, but nonetheless, they're a little more robust. So these are the solenoids again, the old ones, the new ones, there's basically four wiring connectors to operate either blocking or releasing the pressure to raise the system. 

2003 Mercedes Benz SL500 - ABC suspension

And here's the view of where the item's located. So if you can imagine this is on the left front side of the car, the driver's side. This is all in the front, in front of the tire. So there's a cover over the tire. There's your valve there. And you can see pipes, all sorts of pipes here, wires other valves. That accumulator I mentioned earlier is located down here. You can't see it too well, but it's kind of hidden in the black, but as you see, there's a lot of bits and pieces and plumbing to this whole operation. 

Mark: Very complicated.

Bernie: Very complicated. Yeah. 

Mark: With it being very complicated, how often do you have to repair them? 

Bernie: Well, there's a lot of things that that do happen. I mean, I own an SL55 for seven years and the only parts I replaced were the accumulators and one strut. Because I had this clunk in the front that I thought was a strut, but I was fortunate and I sold the car a couple years ago. I go, you know, I think I've had a nice, good run with this car because I know, you know, as it gets older everything's potentially gonna go wrong. 

But we've replaced valve blocks. We replaced accumulators. I had one where one of these high pressure metal lines was leaking. And that was an ordeal of a job too. I mean, it actually revolved dropping the sub frame of the vehicle. Because these lines are, there's like 3000 or 4,000 PSI, you know, pressure, you can't bend or twist these lines. They are solid, hard metal. So you can't, I thought about, can I do this? You know, is there any way we can do it for cheaper, easier? No. It's like you just gotta drop the whole sub frame of the vehicle to run this one line. We've replaced pumps on a number of different vehicles as well. They tend to wear out, leak or not generate enough pressure. 

So those are some of the things. Struts from time to time, go bad as well. You buy the struts from Mercedes they are insanely expensive. They're over 2000 bucks a piece. There are aftermarket suppliers where they're much cheaper. Cheaper by half and they work just as well.

Mark: So you only replaced the front valve at this time. Do you think the back will need replacement soon? 

Bernie: Well, I think so. And we did tell the client because it seemed like sometimes the back would drop too, but it seemed like the front was a more urgent place to start. And so from there, I think probably the rear will be the next thing that needs to be replaced, but you know, this is a very expensive part. It's fairly labor intensive too, but not the worst component to change. It's a fair bit of cost for a car that gets driven mostly in the summertime. So I think the next thing probably the rear will need to be changed, but we figured the front was the best place to start.

Mark: So is there anything that an owner of one of these Mercedes with active body control can do to kinda extend the life of their systems? 

Bernie: Well, you can flush the fluid on 'em and that is a good maintenance service to do every once in a while. And I'd say, you know, once in a while, meaning, every five years type of thing is probably a good amount of time.

So the fluid can be flushed and cleaned and that's probably a good thing to do. It does tend to get black, it's noticeably dirty after a while. The fluid's kind of a clearish, greenish tinged fluid. Not entirely clear, but it's a greenish tinted fluid and it's noticeably black after, you know, I mean most of the time we do these services, the car is probably 10 years old or more. Because a lot of people don't do them, but there's a filter in the reservoir and there's a good fluid service. It's not cheap. The fluid itself is not cheap and you need to run a lot of fluid through it. But it's a good thing to do probably every five years to save yourself some money on replacing the big components. And that keeps things like the valves functioning and moving well, you know, then you, you start getting dirty fluid and it breaks down, it doesn't seal as well. 

Mark: If you're looking for service for your Mercedes with active body control or any Mercedes in Vancouver, the guys to see are Pawlik Automotive. You can reach them at their website, pawlikautomotive.com. You can book online there. They'll get ahold of you. Or you can call them on the phone (604) 327-7112. You have to book ahead to get in to see them. They're always busy. Best auto repair in Vancouver. Thank you so much for watching and listening. We appreciate it. Thank you, Bernie. 

Bernie: Thank you, Mark. Thanks for watching.

About the author 

Bernie Pawlik

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