galileo55

I'm about to replace the rear right Air Spring on my wife's 07 GL450. It's been sagging every now and then.

I also noticed that I'm getting Irregular Tire Wear (Cupping) on my 2-year-old Michelins at 21,000 miles (tread wear warranty is 55,000). Had Goodyear check the alignment: All good. Had the MB dealer check the suspension: all good.

I'm wondering if the car has bad hydraulic shocks in the rear causing it to bounce on the highway and resulting in the cupping. The rear hydraulic shocks don't look to be leaking or anything but the car has 116K+ miles on it and they look like they're the originals. I've only had the car 2 years (Purchased at 92K miles). Just wondering if they had already leaked all gas/fluid with the previous owner and perhaps there's nothing left to leak now.

In the absence of a suspension or alignment issues, why would I possibly be getting cupping, if not from bad shock absorbers?

Also is the front air strut a combination of both the air spring AND a hydraulic shock absorber? Could the problem be coming from the hydraulic part of the front air struts while the air springs are fine (if applicable)?

The MB dealer said they'd have to take the hydraulic shocks off the car to test them to see if they're good.

Any better idea how to hydraulic shocks without taking them off the car?

Thank you

2010GL550

They might be right. I just did my front air springs and was wondering about the shocks too. Until you take the air spring off, I don't think you can tell if the shocks are good. If the shocks are inexpensive, you might has well have them done anyway.

bha

I haven't done work with the rear shocks, but have with the air spring. I can tell you it's very easy to get the air spring out with the truck on a hoist.


They can unscrew the air line to the shock and it deflates enough to pull it out. 5 min job once on a hoist.


Not sure what to make of them wanting to 'test' the shock absorber. I wonder what those cost aftermarket.. they will charge you 1hr labour to remove the bag air bags, then 1hr labour to remove/test each strut. At that point it might be the same cost to take 2 aftermarket struts to an indy and just tell them to swap them.


No need to pay someone to find out a cheap part was no good.. it's cheaper to just guess and replace it. With 100k miles I'm sure it's not as good as new anyhow.


Having said that, I don't know that the rear struts are cheap, so look into that first.

galileo55

BTW, I changed the air spring this past Sat. It took under 1 hour. The easiest non-trivial repair job I've done on any MB so far. One thing I did differently: I could not easily take the compression metal fitting off the plastic air supply line. Tried for a few minutes but was worried about damaging the tube in the process. There's also not much room to work down there. So, I removed the fitting from the new air spring and reused the old one by screwing it in extremely carefully, by bare fingers, as to not cross thread it. Once it was in there I tightened it with a 10mm. It has not lost pressure for three days now so I think it's fixed.

Going back to the hydraulic shocks, the best price I found was for Bilsteins @(USD) $231 online. Not a trivial cost to replace both rears.

With the tire off and the air spring out, I tried to test the hydraulic spring by trying to move the rotor up lifting it with my hands. It was not moving at all. Not sure if that means it's good since it still has pressure. Perhaps it lost the Gas but not the fuild or, perhaps it's good after all. Who knows.

$462 for two is not inexpensive enough to go ahead and change them if they're still good. Hmmmm! Decisions, Decisions!

jhong321

Hello All
I am planing to change the rear airbags this weekend and was wondering if you need to calibrate anything? Local MB shops saids it take 3-4 hrs? after reading a few post i can't imagine it taking that long. Any advise for me before i start?

bha

Maybe MB "recommends" you calibrate something, but I have never heard of it being done and it likely isn't necessary. Didn't do it with my truck and it is perfectly fine.


I suspect they are doing a very expensive (for you) ride height adjustment where they plug in their STAR laptop and make sure the ride height is perfect to 1/64" all around Seriously, in all practical use it's a total waste of money.


Nothing else you need to worry about other than jacking the truck, removing the existing air springs (disconnect the lines first) and then pop in the new ones.


Only caveat is do NOT put the truck back on the ground with the air cells deflated. I lowered my truck to about 1" below what looked like the 'normal' height at the rear of the truck. Then started it up and waited till it lifted itself off the jack. The reason for going an inch or two below normal height is if you put it at normal height, you may not know when the cells are fully inflated because you can't see a difference.


So drop the truck a little bit lower than it should be, start it up, and let it run for a few mins. Then remove the jack and go start on the other side.


You will need long needlenose pliers to make the job easier.. it's sometimes hard to unscrew a small brass nut that's far away with your fingers . But with long needlenose it's simple.

jhong321

Thats for the info. I will try it this weekend

will_w204

My rear air bladders were replaced at 83k CPO for a leak. Rear would occasionally sink overnight. I was told by the tech that shock replacement is much more difficult/labor-intensive because of all that has to be removed to get to them - any firsthand experience would be appreciated if you change the shocks.

FYI, they're just standard gas shocks in the rear, and like any other MB, between 80-120k, they've seen better days.

I had a ton of cupping on Pirelli Scorpions by 10k, but bags and one front strut have now been replaced, and new Toyos put on it, with a fresh alignment. So far, in 4k of driving, tires look, sound and feel great, but 4k isn;t much. I suspect flaccid rear air bladders may have contributed to the tire wear, but I'll definitely do shocks before the next set of tires

Canuck714

Hey guys, I just noticed that my wifes 07 GL 450 will occasionally bleed down on the drivers side rear.
If there is a problem with the bladder, I cant imagine that it can seal itself some of the time and bleed out quickly others.
Is there a valve that I should be looking for?

cozkay

I have the same problem with drivers side rear. Sometimes it will stay up for days other times a quick trip to the store and back it will be completely down but on start it pumps right back up... Don't know what to make of it.

Fourdiesel

Erratic bleed down - sometimes does, sometimes doesn't - is almost always related to a valve or valves somewhere in the system which stick or leak, including control valves and their electronics. As was stated it is impossible for a leaking bladder to repair itself.

usmc6042

Rear has air bags (500.00) for both then shocks (660.00) for both. Repair cost I will tell you next week they are in the truck of my GL ( right now)

N_Jay

Rear shocks are a 3+ hour job at the dealers.


There are a fair amount of interior parts that come off to get to the bolts.

will_w204

I landed here via keyword search..

Posted by BHA: "I suspect they are doing a very expensive (for you) ride height adjustment where they plug in their STAR laptop and make sure the ride height is perfect to 1/64" all around Seriously, in all practical use it's a total waste of money."

My 08 GL450 has had left front strut, both rear bags and both rear shocks replaced in the last 1-2.5 years. I found it sitting an inch or so too low last week, twice, just like last summer, when the first 90* day we had produced the same effect, and they found via leakdown that the rear bags were leaking. This time, they claim they can find nothing leaking, but tried to sell me a "ride height adjustment" for $225. Yeah, go **** yourself.

I guess the fact that my truck has probably had $10k in CPO work done means that they've hit the secret "nuh uh!" ceiling that MB will allow them to expense for single-vehicle CPO repairs.

The first Benz I bought from a dealership came with a Starmark warranty. Starmark is the single-biggest reason I am on my 3rd used Mercedes. If there is one single factor that would cause me not to come back to MB next time (aside from the soon-to-be joke of a load of CPO CLAs, GLKs and other faux-Benzes polluting the lot these days), it's the *******ization of Starmark into "CPO" a few years back, which basically all but gutted MBUSA's previous standard as having the best used warranty, bar none.

Are you listening MBUSA? Make your money by pawning crappy CLAs and GLAs off on 25 year olds who just traded their 2002 Camry for your car. Maintain loyalty by backing up your vehicles like you used to.

eric_in_sd

Rear shocks are a normal wear item. I did mine at 88k miles. It was something like a $900 job, with parts, at an indy mechanic.

N_Jay

How much better did it really ride?
Most shocks today are good till they leak.
I have one at 120K and one brand new and notice no side to side bounce as if they were un-matched.

eric_in_sd

Eh. Somewhat better. Not a huge difference. They said one or both shocks were leaking; I hadn't noticed.

I only got to figuring that something was wrong when I swapped the tires front-rear and suddenly thought I must have front wheel bearings going out. Turned out it was cupped tires.

I looked at it this way: If the shocks last 90K miles, and I'm not likely to still have the truck at 180K miles, and before 180K miles the ride will really turn to crap if I don't change them, then may as well change them now.

will_w204

Seconded. They replaced mine under warranty around 85k. The only difference I noticed is very slight improvement in rebound-control when going over a reallllly severe, sharp dip on a local road. It doesn't rocket upward as high coming out of it, but other than that, zero difference