MYD-WGN

http://forums.quattroworld.com/allroad/msgs/34738.phtml

STL_allroad

So this is my question. If my suspension is leaking in an unknown area and my compressor is running alot, what does changing the compressor do?

Mr. Timewise

Have you used the Jack mode to determine which air spring is leaking? We need that information first.

STL_allroad

I just replaced my fronts, Ill put it in jack mode over night and report back in the AM

STL_allroad

I left it in jack mode all night with no drop in either corner. About once every week and a half or so I will come out and it will look low. I start my car and it will be on level one blinking level two like its raising up. Are there any valves in the compressor which would leak due to alot of use? Cant seem to figure out why it would run so frequently if no air is leaking from springs...

all(over)road

Nothing...the new compressor will run just as long if the leak is still present.

Typically when they run alot due to compensating for a leak they'll wear out and are noticeably noisey. Its too bad they didn't design in a failsafe to save the compressors from burning themselves out.. Folks have lubed them with air-tool oil thru the air inlet in the spare tire well to quiet them down but that doesn't 'fix' anything.

STL_allroad

I am guess I am pretty confused on what could be leaking now that i lost no pressure or ride height due to jack mode. As soon as a drove off this morning my compressor turned on twice within 5 minutes and then i didnt hear it again by the time i got to work. I wonder if this is just normal for suspensions with wear... Does extended use of the compressor cause it to not pump with the same efficiency as it would be new? Maybe thats my problem...

Mr. Timewise

It may be worth mentioning that as a car is driven, the air inside the air springs gets warm as the suspension flexes. When the air gets warm more pressure builds up and the suspension is raised. The suspension controller then releases air from the air springs to compensate, lowering the suspension back to the level you've chosen.

Then, when you park the car, the air inside the air springs cools down...especially if you park overnight when the air temperature is typically lower...and the air pressure decreases. This causes the car to sink. If you are not in Jack Mode, opening a door after the car has "lowered on its own" signals the controller to use the pressurized air in the accumulator to raise the car back to the proper level. If the accumulator doesn't have enough stored air pressure, the car will not be raised. When the ignition is subsequently turned on, the air compressor will power on and immediately re-pressurize the system. The suspension controller can then correct the air spring levels as needed.

----

Since neither side is dropping while in Jack Mode, it is unlikely the problem is with the air springs or the hoses to the air springs.

As you suggested, the old air compressor may simply have a very hard time pumping air, so it takes forever to pressurize the system. It may also be that there is a leak in the hose connection between the pump and air distribution valve body or the accumulator and the air distribution valve body. Are you able to crawl under the car and spray some Windex on the hoses at the air distribution valve body?

STL_allroad

Thanks for the insightful logic. I am going to try to get under there this weekend. How can I safely do it? I picture me under there and doing something wrong and having the car drop down on me... How hard is it to get to the compressor and the air dist. block?

Mr. Timewise

The air distribution block is forward of the spare tire well. The air hoses are directly visible...nothing has to be removed to see them. The pump has a cover which can be removed (two 10 mm hex head bolts I think), but doing so will be a dirty job because the cover accumulates dirt on its upper surface. Plus, it may be that the bolts are nearly frozen in place. Test the air distribution block first.