ChrisDavis

I just replaced the passenger side front strut as well as the compressor. WIS says to fill the air bag before lowering the car. I went into STAR and was able to start filling the reservoir. I stopped at about 11 Bar. My question is, does this fill the air bags also are do I need to trigger valves?

2009 GL 320

Thanks
Chris

eric_in_sd

Couldn't tell you what happens in STAR, but you really don't need to do anything special. In fact, I would not specifically pressurize the bags with the suspension extended - why would you want to put a bunch of air in the springs that will only have to be released?

I assume you have it up on a floor jack. Just lower to below ride height and then start the motor and open, close the doors, etc. The system will seek to normalize the ride height. Because the motor is running, the pump will run.

One time I lowered the truck all the way to the floor. Couldn't get the jack out until I ran the started it up to raise the suspension back to normal. It kinda looked cool having a lowrider sitting in my garage.

expl0rer

I just replaced a rear airbag yesterday. Running the motor did not help, not sure why the pump wouldn't start. It had in the past when I have had the rear lifted and needed to pressurize the suspension after. But raising the suspension while the motor was running kicked the pump on and filled the bag, the truck lifted off the hydraulic jack and that was that.

I had the truck resting on the jack with a stand under as a safety if the jack bombed or lowered unexpectedly. That's when I was raising the vehicle. During actual work, two stands always to hold the truck up. I'm a little paranoid and OCD lol

ChrisDavis

Expl0rer, I had the same experience and am also OCD. I did notice this morning that adding air to the reservoir yesterday raised the rear end off the jack stands. I had replaced the rear shocks yesterday and put my small jack stands under the rear to keep it from bottoming out. I am assuming it worked and has enough air to keep me from damaging the bags.

expl0rer

If I understand correctly, your vehicle was resting on the stands before you added pressure to the reservoir. After adding pressure to the reservoir, the vehicle raised enough to release the stands? Were the rear tires in contact with the floor before adding pressure? If yes to all questions, you should be good. From one OCD DIYer to another, you can raise the vehicle with the button (or dial, if you have the offroad package) and monitor the front/rear while it's going through the process, then lower it. All corners should settle in relatively equal height and you should be good.

I don't have DAS and have not had issues with filling the bags with the motor running and raise/lower process, except the very first time replacing a rear airbag when I had wound the level sensor during installation and it was sending a value blocking the valve block from filling the bag. User error! After fixing my mistake, it worked just fine.

I've since discovered that there's no need to disconnect the level sensor in the rear. I was just too paranoid the first time. 😃

eric_in_sd

You have to rub your tummy and pat your head while facing north by north west, hopping on your right foot, and reciting Mary had a Little Lamb.

The system checks suspension height when you open and close the doors. Also when you're driving, of course.

It won't run the pump with the motor off. Power drain, or to mask the pump noise?

It's a bit odd to pressurize the bag with the spring extended (i.e., lifted). When you lower the truck back down on the springs, the air inside will compress, and who knows where it will end up. Just lower to the point the suspension is lower than normal ride height, and then begin the ordinary height adjustment procedure.

eric_in_sd

The only way pressurizing the reservoir would cause any change to the spring pressure is if the valves in the block were activated or leaky. You could have instructed the system to activate without realizing it, e.g. opened or closed a door, or by thinking bad thoughts.

It's annoying how f'ing clever the system tries to be. When I open the door to get something, and I hear the suspension doing its thing, it's like the beast in the cave is stirring in its sleep.

I don't think there is any risk to static lowering onto a deflated spring. It just comes to rest on the bump stops. Driving on the bump stops is probably a pretty bad idea. I never even thought about it; like I said, just lower all the way to the floor and then have fun watching it lift itself.

Max Blast

If doing the rear bags and you didn’t disconnect or move level sensors (which you shouldn’t) you can use one jack placed under the hitch and gently let it down to close to the bump stops. The compressor should then engage and lift the car off of the jack.
just don’t let it slam down on the dirt and you’ll be fine.

expl0rer

I'm a guy, you can't be seriously asking me to multitask with most of my extremities and mouth simultaneously! Come to think of it, a politician would be able to, but I'm not one of those either!

expl0rer

That's exactly where I lift the rear. There is a cross member on the chassis right behind the rear diff where the stands are placed. Be VERY careful with the stand placement, you do NOT want the stands to get in contact with the diff case.

eric_in_sd

That is where a couple of 2x4 chunks come in handy. The cross member is recessed about three inches. Can't tell you how many times I've muttered over and over, not the diff not the diff not the diff.

Put jack stands on the outer jacking points, in front of the wheels and under the doors. I believe for safety you are better off with the stands as far apart as possible.

Max Blast

Never the diff. Just so that’s said.

expl0rer

A while back I picked up a couple of pucks which mate to the jack pads of the car and sit on the stand or the hydraulic jack. I bent a rocker once on an old car with a jack and took me months to get over my mistake. Broke the paint too. Can't have the same mistake happen twice.

eric_in_sd

Did you get something that fits well? I was considering cutting 2x4s to fit, and then embedding disc rare earth magnets in the faces to hold them semi-permanently on the frame. Drill holes, push the magnet in, first time you jack up, the magnets would be pressed in the rest of the way. Big rubber blocks would be better, though.

expl0rer

Not a perfect fit, but works. For the price. I ordered two, in red, so I don't lose them and can see them easily in the mess that I make with tools amd parts.

POTAUTO Aluminum Jack Pad Jacking Puck Adapter Support for 2000-Present Mercedes Benz Vehicles (Qty 1, Black)

Amazon

Amazon

The puck is smaller than my jack's lifting plate, which is fine. I thought that the rectangular piece protruding from the puck would be a close fit into the rubber pad on the GL, but it is smaller and the puck will easily fall if left unsupported. I guess the positive is that you couldn't forget the puck mounted there and lose it later when you're driving. If I wanted to, I could just wedge some cardboard or something else to make the fit tight enough. With it being loosey goosey, I have to be careful not to get my fingers between the puck and the jack, while supporting the puck with one hand and lifting/pumping the jack with the other. It takes a couple of tries before I get the alignment right and all fingers are still accounted for.