Air suspension hiss

(Jwarrenr6) #1

My 2006 VDP hisses from the front for about 10 secs when i park on my sloped front drive. is this normal / just the compressor leveling the car?

(Richard Schwartz) #2

It could be normal. The system has a number of modes it enters depending on what state the car is in. Mine always hisses when I first unlock it, after it has sat for a while. You’ll hear this one from the left front and is the system purging moisture. Next you will hear a deeper hiss while the car is leveling. You may also hear the compressor running in the left front wheel well as it refills the air tank. I can’t recall hearing a hiss when I’ve parked (my drive is slightly sloped) but I have noticed that the car sits level (tail up) on the drive. Here’s a page from the shop manual describing the states of the suspension. Hope it helps.

(Jwarrenr6) #3

Thanks Richard. Yes I notice it occasionally when unlocking, but most when I have a full load, and then park. Sometimes when I park on my sloped drive, and I do see the front end dip a little and the back rise.

I guess its something to keep an eye on, but I wont go looking for a compressor just yet :blush:


(Richard Schwartz) #4

Jim, Just wanted to let you know that I heard the hiss in the rear after I parked. It’s an adjustment using the air in the reservoir which is located in the trunk (boot).


(Larry) #5

Hi Rich…just joined the Jag Forum. Found your air suspension chart interesting. I own 2006 xj8 and have found that parked in the garage (level) I find the front end to be lowered after not driving the car for 3-4 days. Owned the car for about 7 years and have secured fittings on the air shocks and monitored for leakage with water (air bubble test at fitting). Very tight, extremely minimal to no escape of air. What do you make of that? Front end height levels on start up almost immediately and the compressor does engage to assist.

(Jwarrenr6) #6

Yeah I do hear the hiss after standing for a day or two as well. The car sits OK, and I dont have any alarm codes, so i guess it’s good.

(Richard Schwartz) #7

Hi Larry, welcome to the forum. I’ve come to expect some amount of lowering. Is the garage cold? That could make the car settle a little due to the air in the spring compressing. There are also fittings in the boot that can leak: the valve block connections to the front springs. You mentioned a minimal air leak. It might account for the loss.

When I first replaced my fronts I tested the air connections on the valve, as you did, and found nothing. But as the soapy water overflowed and ran down the shock body both fronts showed bubbles at the bladders! I bought the car in spring and it took until the colder fall temps. Before it really showed. The compressor usually handled it but sometimes it took some driving, which raised temperatures, for the struts to stop leaking.

Like I said, seeing the front only slightly down (not chin on the ground) and the fact that the car is sorting itself out right away does not sound concerning. It’s an expensive and bothersome job to do (with some gotchas that will have you visiting the dealer). I replaced mine with Arnotts’ which were ½ the price of OEM. They do have a lifetime warranty where they will send you a brand new strut. However they are now making them in-house and they do not contain the active electronics for such things as lowering the ride height at speed (I’m not sure the XJ8 had that). There are others around but I don’t know much about them.

Anyway, check the connections at the valve block (in boot near spare tire) and bubble test the entire shock. If all you find is that small air leak, maybe try some thread sealant. It seems to be not “normal” but “expected”.

Best of luck