Hi all, my first post on this forum. My 2011 ML300 CDI has done 198k kms. Started hearing a noise coming from near the alternator, a while back which would normally happen after starting for 10 or 20 seconds, and sometimes again when idling, but rare when driving, so no difference if cold or warm engine. In parallel Airmatic Malfunction would display from time to time, but usually not be present when engine was started the next time. All through this ride was good, and no obvious issues with ride height on all four corners, and even now all seems good. I was thinking the noise could be the suspension compressor, and in last couple of days noise became very loud and definitely sounds like a compressor noise. Still goes off after 20 or 30 seconds, but noise is something that is too loud to tolerate even for the short time.
To make sure, I removed the fuse for the compressor, and at idle no noise, so definitely the compressor. I know there is possibly a leak elsewhere, but based on the mileage I expect the compressor is due to be changed, so will start with that, and then check other components. Can not get a new compressor locally at a reasonable price, so purchasing one that is in another city in Australia, so will take a few days to get it and another couple before I get a chance to do the swap. My questions for this forum are as follows:
1. This is the family car, and during the week it is used for local driving to school and shops by my wife. Smooth roads at speeds around 60km/hr. With the fuse out, and the compressor therefore disabled, can any damage be done to the other air suspension components if driven slowly and carefully for these 2 or 3 km trips. My gut feel is that it could, as well as possibly be dangerous if sudden changes in direction or emergency braking is required. I know my way around cars, but this is my first experience with air suspension so not sure what would happen if driving without the compressor. If the car can not be used for a week it will be inconvenient, but further damage or safety is more important. Anyone know if there will be an impact?
2. Anyone with experience changing a compressor after close to 200k kms, recommend other minor parts to order and change at the same time (like mountings, hoses, air filter etc), because they might need it, and it is easier to get it done while there, then going back again to change them later, and their cost is relatively minor.

Appreciate the experience and advice from others on this forum for the above. Thanks in advance.

 

smat front yard repair folks go to startekinfo and get all the applicable WIS repair docs------others keep coming back here whining.

 

The thread below has all the Airmatic documents you need. Look within for compressor replacement

https://mbworld.org/forums/m-class-w...e-install.html

 

Thanks, that is amazing amount of information. Will be very useful. I will search for what I need, but if anyone knows if it is safe to drive short distances without doing any damage with the compressor disabled, it would be very helpful right now, as I am not sure I will find the answer to that question quickly. Really appreciate you leading me to those documents though.

 

The compressors run on for 2 reasons - most likely because you have a leak and its topping up the reservoir. So driving with a disabled compressor is only going to lead to a depressurised system somewhere. I wouldn't think that's safe.

The other reason the compressor might come on is a faulty relay that allows it to run too long. When you replace the compressor, they give you a new relay to go with it.

 

Thanks appreciated.

 

its easy, it took my about 30 minutes to do my ML63. Only 3 bolts holding in in place. Make sure to change the 3 bushings when you change the compressor.

They do not come with a new compressor so you have to order the 3 bushings separately. I did not change mine and had some vibrations when the pump turned on, the new bushings solved that problem.

ML63 driver

 

Thanks for the comments. I considered ordering the new bushings but delivery time would have slowed me down. They looked in good order when I removed the compressor, so reinstalled the old ones and no vibration or other issues that i can see. If i get some vibrations I will order and replace later. I have another question though. My compressor did not come with a new relay, however it is working fine and does not run very long or often when I do hear it turn on. Not sure it makes much sense to replace the relay in that case, unless someone has a recommendation why it should be replaced.
Another piece of information on my install. The airline fitting and retaining collar that came with my compressor were too small for my airline. I am thinking it may be possible that the airline on the ML is larger than sedans and other smaller vehicles with airmatic. For those living in Australia PIRTEK is the best place to get fittings, although as the thread into the compressor is unusual size at 10mm with 1 mm pitch I needed a few pieces of hardware screwed together from the thread to the airline to match the sizes (airline is apparently 1/4 inch which i think is strange for a Euro vehicle). Also the PIRTEK fitting to the airline is far superior to the original. It is a pressure fitting that you just push the airline into and it's "teeth" inside grab the airline and the more you try to pull it out the harder it grabs. Much better and less fiddly than the original collar type retainer that was on the original compressor and came with the replacement compressor.