RESOLVED - Audible knocking noise from air suspension compressor - replace or rebuild?

ajkenned

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Hi all,

Vehicle info: 2013 LR4 5.0L, 140,000kms/87,000miles

I have an audible knocking noise that I have diagnosed to the air suspension compressor. No codes thrown when I attach the GAP tool, so its almost certainly something mechanical gone wrong in the pump - its like there is something going on with the piston as it sounds like its running but really noisily. It still maintains normal height ok, raises or lowers more slowly, and the rest of the suspension is fine.

If anyone has experience - is this something likely to be serviceable with any sort of kit out there, or should I just front up for a new compressor?

If its serviceable, can I drain the system using the GAP tool, or do I need something else?

Thanks in advance.

Andrew
 

ajkenned

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I've found a few threads - one indicating the possibility of dirt between the frame and the compressor leading to this. Another suggesting the possibility of moisture in the lines. I'll take off the guard and give it a good inspection and clean.

This thread seems to match most closely with what I'm experiencing: https://www.landroverworld.org/threads/is-this-normal-for-an-amk-compressor.42727/

The problem appeared after a very muddy and wet drive on the Dempster Highway in Yukon, Canada - several hundred kms of muddy dirt road. There was a mix of a freeze/thaw cycle, rain, and visible calcium chloride on the road. So, its possible either one of those could be the issue. It took me 10 minutes to pressure wash 1-2" of mud out from each of my rear wheels after the drive!
 

ftillier

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You can release pressure via the GAP tool, but when the car is off, there's not a lot of air volume in play if your center valve block is working properly: just the air in the line between the air compressor and the center valve block. First thing you'd want to check is which compressor you have, AMK or Hitachi. I have only seed rebuild kits for the Hitachi, including new piston seals/etc. Have you recently jacked the car up? The reason I ask is my compressor clattered more when I snapped the compressor mount due to improper jacking. Compressor itself was fine despite bent mounting points.

If you decide to pull the hoses from the compressor, just support the car with jack stands so that you don't get crushed while working underneath if the system does lose pressure. Disconnecting the hoses (both the output to the center valve block, as well as the intake and exhaust on the rear) requires first pushing the hoses in to release the 'teeth' of the connectors, depressing the release collars, then pulling the hose out. You can remove the lower compressor cover by removing the bolt at the bottom, and two torx screws at the front/rear of the cover. Then it's just snap connections holding it to the top half, and you should be able to clean it out. Hopefully it's just a matter of cleaning things out.
 

djkaosone

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If you have a Hitachi, there are kits to rebuild your piston to increase compression. AMK is not rebuildable at this point in time. You should probably take the compressor out whether it's the Hitachi or AMK and bench test it for the knocking sound. Just add 12v power to hear it run and then make your decision.

The gap tool can deflate your air system, pro tip, just make sure you have the truck on jack stands first.
 

ajkenned

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Silent compressor operation restored.. when I removed the extra guard (which has been a saga of its own), it was caked in as much as an inch of mud on the bottom inside. I removed the lower half of the plastic tub containing the compressor and found it also clogged full of mud.

I think that the moisture and thickness of the mud on the road I drove meant nothing drained out, and the mud just built up into a giant cake. Now that I've removed all of the mud and opened up the drainage holes on everything again, we're all good!
 

CRYA

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If you have a Hitachi, there are kits to rebuild your piston to increase compression. AMK is not rebuildable at this point in time. You should probably take the compressor out whether it's the Hitachi or AMK and bench test it for the knocking sound. Just add 12v power to hear it run and then make your decision.

The gap tool can deflate your air system, pro tip, just make sure you have the truck on jack stands first.
Is there a recommendation for a rebuild kit? I’m seeing some unknown brands for about $100 and not sure of
 

djkaosone

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Is there a recommendation for a rebuild kit? I’m seeing some unknown brands for about $100 and not sure of
I've used this one with good success. Hitachi Piston rebuild or just search on Amazon for "X8R Hitachi", they have a lot for it. As far as the drier goes, get oem. I had a few rebuild kits or new aftermarket that either leaked or cap totally blew up.
 

ftillier

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I used the X8R desiccant kit (without the new cap) to refresh my dehydrator and don't seem to have any leaks. Happy I did that as there was a fair bit of fine powder from the 10 year old desiccant. When I took apart the front valve block I noticed faint traces of powder there, but all seems to be working fine.
 

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