Hprd

I have an 04 allroad with the 4.2.

The level control system works but it is extremely slow to adjust/respond.

My question: is there a way to test the compressor pump's output? I would like to know before replacing a very expensive part that this indeed is the issue.

I tentatively have a pump on the way with my mechanic but it seems there would be some way to test the output.

Any help appreciated.

finiki

If you are near 100k it is doing things much slower than it did new.
I replaced mine at 100k and it was way faster & quieter.
I see Arnott raised their price but it is still the best deal (unless you buy the Arnott Mercedes version and retrofit). There is often a 10% discount code out there somewhere too.
http://www.arnottindustries.com/part...17_pid124.html

Werecar

current code for 10% is 74V4-W7D

Hprd

So you are agreeing that this is the problem (weak compressor)?

Thanks.

finiki

I am a name on a forum, just my opinion. I am not aware of a test, if your system normally holds air (as in overnight) than the issue is likely your compressor. You and your mechanic are the real time analysts.

Hprd

Yep, holds air. Has new bilsteins. Works as it should as far as adjusting based on speed or on demand. Had a few problems when it was low single digits and was trying to raise the car up from level 1 to 2.

Takes about 1 1/2 minutes to raise from level 1 to 2 hn coming off the interstate and the light starts flashing. I have about 108k miles on the car BTW.

I find it hard to believe there isn't some way to test the pump.

05allroad

Don't know a specific test for head pressure or to see what kind of volume it's putting out (although I wouldn't be surprised if you could see these with VAGCOM. I know you can tell when the compressor is on/off and when the valves open/close too...) but I'd say with almost complete certainty that your compressor is on it's last legs.

About 2 months ago, I started having the same issue when going from L1>L2 after getting off the highway. About 2 minutes to re-gain L2. Then I started noticing some issues overnight when it was below freezing - no visual level drop overnight, but after driving for a minute, the L2 light would start flashing to regain L2. 50% of the time it would succeed, the other 50% I'd get a suspension error light in the cluster, but turning the car off & back on would clear the light and allow me to get back to L2.

Swapped out the compressor ~2 weeks ago. There have only been a couple of very cold nights, but (knock on wood) it's no longer having the issue overnight. And level changes now take about 15 seconds.

My best guess is that the compressor was dying and having trouble keeping the pressure up with the cold, dense air.

I'd like to get thru a couple of cold weeks before declaring the problem resolved, but things are looking good so far.

allroad in SF

My pump started rattling and making other strange noises at about 75K. It was working slower too.

Replacement did the trick