BusinessConnect

Greetings from Australia.
I've recently acquired a 2007 Mercedes GL320 Diesel and it's a fantastic leviathan of a Vehicle (My Kids called it the "Panzer" because it's a Tank)

​​​​​I've had some issues with the "Compressor Cooling Down" Error....I figured based on past experiences with Land Rovers etc that the Air Suspension Compressor was dying... Bought a replacement and fitted as well as getting the better Hella Genuine Mercedes Relay and the issues continue.

The Car doesn't lose height at all overnight, so I believe that means that the Valve Block and Springs themselves should be ok. The Intake Hose to the Compressor was damaged at the End so I chopped it down and checked rest of the hose was ok....haven't replaced the Filter as yet.

Should I be looking at potential leaks towards the Air Tank in the rear? I was hoping for some potential knowledgeable hints and tips as to where to look next.

I find if I keep the car at Off Road Height 1 it's fine, until I go above 110km or so for a while and then it goes down the the Normal Height and very shortly the car feels like there is no suspension at all and my back jars nastily...

I press the height adjustment up and at that point I get the Compressor Cooling Down Message.

I've removed the 40A Fuse to disable Air Suspension Compressor for now and see how it goes without that before I can get troubleshooting on the weekend.

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BusinessConnect

Just an Update:

Did around 30 Miles/50km today with the 40A Fuse Removed. Car didn't report any issues until I started up on an Uphill Climb and it then stated "Malfunction" with the Height Symbol in the Centre Display Behind Steering Wheel.
When I got home Car seemed to be at roughly the same gap between Rear Wheels/Front Wheels and Top of Wheel Arch etc... so didn't appear to have any leaks in the system.

I will pull out my MaxiDAS DS808 Code Scanner Tomorrow to see if there is a sensor issue or similar.

Max Blast

Hi there.

your code reader will tell you where to look - in this case the compressor is shot; but why?

most often due to leaky airbags. Since you say your rear sags that would indicate a leak in the rear bags.
see if you can fully raise the car and spray them down with soapy water or leak detector. It’ll be obvious.

if not, rear airbags are fairly cheap and take about 15 mins a side to replace.

BusinessConnect

I don't believe the compressor is shot because Ive replaced it... I don't get sagging when the car is parked at All...if I had leaking bags surely the car would sag then...

Max Blast

you should absolutely go check for leaks everywhere - with a leak finder or soapy suds. My point was that most often, it is the rear airbags that leak - it might not be evident when parked overnight, but when the suspension travels it can uncover a small rift or rear that is otherwise sealed when stationary. It then leaks while driving, keeping the compressor on most of the time.

how old are your rear bags?

DennisG01

It's quite possible for leaking bags to NOT leak while the car is just sitting overnight. However, you drove around with the compressor relay pulled out... and there was no sagging during driving or after sitting overnight? That probably rules out the bags (and lines) at a 99% certainty. I would imagine that the error you received while driving may have been because the level sensors were calling for adjustments, but obviously nothing was happening. You mentioned you have a new compressor, and while that doesn't mean it's not defective, it certainly leads you towards a leak somewhere else. If that scanner is advanced enough to do tests on the system, that's good. The reservoir tank is a good possibility as being the culprit.

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Lunchtime Update (Melbourne Australia Time)
I've sprayed the Leak Check Spray around the Front Struts Connections (No Bubbles) and at the Rear Air Reservoir Tank Inlets and Join between the Tanks (No Bubbles).
I've read the Codes with the Code Scanner and I get

Error Code: 5503 - Recovery Time during filling of central reservoir too long
Error Code: 5111 - Check the Component 'B24/4' (Right Front Body Acceleration Sensor)

Those are exactly what the MaxiDas DS808 give me as descriptions.

I've cleared these codes now and they haven't come back as yet... However I will take the car for another drive and see how I go.

BusinessConnect

Update after a drive
1) B24/4 Error re-occurs.

I've since discovered the diagnostic menu in the MaxiDas and was able to test each pneumatic valve etc... What I'm left with is the following.
Component Y36/6y2 (Right front level control valve) is not operating properly or the line between the valve block and the suspension strut is not leak tight.

This pretty much leaves me to believe I either
a) Have a Faulty Valve Block or more likely
b) There is an issue/leak with the Right Front Strut.

I'll have a look at the lines etc from the Valve Block to this particular strut to make sure they aren't loose etc but looks like I might have found my issue.

All of the other Tests of Components were fine/around the same values.

BusinessConnect

Right Hand Strut/Airbag is the Culprit... It's leaking massively out of the bottom... doesn't appear to be attached to the Strut at all..
Interestingly this side seems fairly generic/original where-as the Left Hand Side looks to be Arnott Strut..

DennisG01

At least you found the issue!

Max Blast

Allright!

looks like the scan tool directed you to look at the actual culprit, with the limitation that it cannot test each individual air bag -only the line from the compressor to the block, or the line from the block to the bag (which would include the bag).

Just thinking ahead, your compressor has been working hard to fill the atmosphere through the leaky bag. do you have an option to test the compressor output? The test threshold is 16 bar within 40 seconds. a new compressor should reach 16 bar within 1-2 seconds.