I'm a fairly new owner of a 2017 GLC43 and have noticed a few times lately that my rear suspension sags when the vehicle is left for a while. When I say sag, the front stays put and the rear drops to a level that I suspect is as low as possible - tire is sitting well up inside the fender. The vehicle hadn't done that at all in the first few weeks of ownership. There are two variables that I can think of that might have started this but it could also be something else and perhaps it is just something new and the timing is coincidence.

The first thing I did was change over from the winter to summer tires. I jacked the vehicle one corner at a time with a floor jack. I did open the rear hatch while jacking as I've read that this might lock out the air suspension. After changing the tires, I don't think the sagging happened until after the other variable came into play at least a couple days later. In other words, it didn't sag for at least a couple days and then I took it out for the first drive after changing to summer wheels and parked it in Sport mode. Prior to this, I don't think I had ever parked it in Sport mode, always in Comfort or Individual (which has suspension set to Comfort).

I tried parking it with the suspension in the fully lifted mode and it did not sag, even after being left for about a week. I've parked it in Comfort since then and it did sag. So, given that it doesn't sag in fully lifted mode, I'm thinking that it isn't a mechanical issue like a leaky bag. I suspect that would also result in only one side sagging but it is dropping all the way down on both sides in the rear. Perhaps it is related to a software setting that was somehow put in play after parking in Sport or after jacking. Not sure.

Big question - is this something to worry about? Is this a sign of a big problem coming? Anyone else have this experience with their GLC43 or 63?

I do still have warranty so I may check with the dealer to see what they say.

For reference, here is a picture of it in "sag mode". Thanks for any advice of feedback anyone has.

Double post.

My GLC sags if it sits untouched for two or three weeks, but it comes down on all four wheels. The car returns to normal ride height upon engine start.

I have never heard of this. I would get it checked out as this is def not normal.

Yep, that's just weird....

By any chance did you hit the lid assist button in trunk? That drops the rear to as low as possible setting. There is a switch in the trunk on left side next to the seat down switch.

KING

I'm aware of that button and I don't think this is the issue. The car has done this multiple times now without the hatch even being opened.

I think it’s coming from a leak in your AirMatic suspension system.. Seems to have a leak when it sits but rises when the engine / air compressor kicks on.. Or something like that.. Wish you all the best and hopefully still under warranty..

Had it in for a look and they found a leak in one of the rear bags so that will be replaced under warranty. Didn't have the part and will take a couple weeks to get it in but glad it is under warranty. I hope this isn't a common issue and that I need to worry about the other side having the same issue in the near future. Car currently has just under 80,000km so getting in just under the wire for warranty coverage.

Just another update to close the loop on this. Got the car back after the replacement of rear suspension air bag and noticed that it was still sagging after sitting. Took it back in and they found the air bag on the other rear corner was leaking. Not sure if this is just coincidence and back luck for me, if there is something about the way this car was driven, the conditions where I live, or if this is a potential issue for all of us to look forward to.

As a reminder, I bought it used with about 75,000km on it and it is a local car, having the bulk of its mileage put on in the Edmonton, Alberta area. Vehicle has just under 80,000km so still a very small warranty window left on it but it was also CPO car with added two years and 40,000km.

I ventured over to this forum because the air suspension is more common among the GLC AMG's than the non-AMG ones. I've been researching this issue too, because my '16 GLC300 (20k miles) squats after sitting for a while, but it does it evenly from front to rear and side to side and returns to normal upon startup. People say this is rest mode, but nowhere in the manual does it say the system has a rest mode. I did read somewhere that squatting when parked for a while could be a level sensor gone bad, not a leak like commonly thought. Usually when there's a leak, the car unevenly sags. I wonder if your dealership isn't diagnosing the problem properly since the problem continued after the first air bag replacement, it wasn't sagging unevenly at one wheel, and what are the chances both air bags started leaking??

I wasn't aware that the non-AMG models came with or could be optioned with air suspension. Regardless, they did say that they found a leak in both sides at the rear and while I'd agree that it would be quite the coincidence for both to go at the same time, after they replaced the second side, it hasn't sagged at all. Good to know about levelling sensors though as that certainly has some logic behind it.

Yep, an option on non-AMGs, but standard on AMGs.