Air suspension concern

[Bucky1]

2011 Denali
Recently I have noticed every time I start up, even after only a short period parked, the air pump kicks on, and I will get a dull thump from what sounds like the front right after it runs for a moment.
I don't recall this in the past. Any diagnosing I can try or look for?


Oh unrelated....120k miles. Love this vehicle. Except for the head room. I'm tallish. These seats won't go down far enough that I don't touch my hair on the ceiling. Both front seats all the way down and both are like this.

 

[Big Mama]

If the compressor runs a lot it’s either a bad shock bladder or the pump is going bad. The pump is more toward the middle but could still be the noise you’re hearing. If you get under it and have someone start it you’ll have a better idea. Take pics if you can.

 

[RST Dana]

Look under the rear, driver’s side. Pump is there. I just replaced one shock because of the same issue. The initial startup cycle is expected, but frequent cycles without weight changes are not. Rock auto has a code here for discounts.

 

[Costal_Cat]

@Bucky1 the air compressor is only utilized by the Rear Shocks. So if the sound is truly in the front it is not related to the compressor. Doesn't mean there is not a compressor issue and it just sounds that way. To the other replies, you need to check it out from the rear.

Good test sequence would be

1. Does self-test run, if no then you can check the fuse, the relay and jumper the connection to see if it works bypassing the relay.

2. with the truck running throw the kids, dogs, the whole family in the back, a sack of cement to see if the truck will level up. You should hear the compressor kick in then the shocks fill and level.

3. Get everyone/everything out and you should hear the shocks release air and come back to level.

If any of that doesn't happen then there are a variety of things to check but that should help us point you to where you might need to focus

 

[Doubeleive]

if you have autostart do this: go stand by and crouch down near the drivers rear well area, hit the autostart button, just before the vehicle starts you should hear the pump release a little air and then right after the vehicle starts you should hear the pump run for a few seconds normally about 5 seconds (roughly). then shut the vehicle off and keep listening. in about less than 1 minute you should hear the pump release air again.
it is normal procedure for the pump to do this everytime you turn the key start, regardless if it has been 30 seconds or 5 minutes or hours.
if the pump is running for a longer time or if it turns on and runs while the engine is on for no apparent reason then it "could" be a indicator of a leak in the lines or a bad rear air shock bladder, you can spray the rear shock air bladders with a mix of soap and water and do the same procedure as noted above and see if you see any bubbles from a air leak.
the pump does a self check each time the key is turned to run, it releases air to make the initial pumping procedure easier on the pump if the release valve is stuck you wont hear it release air in which case the pump may not run everytime the key is turned to run.
there is a TSB that notes that the pump may not run everytime which conflicts with the normal operation procedure, mine had a slow leak and I ended up replacing the shocks and pump and everything is working exactly as noted for "normal" procedure again. rockauto sells the arnott remanufactured air shocks with a lifetime warranty. if you need to replace the pump arnott makes that as well but you may find better prices by shopping rockauto/amazon/ebay and comparing prices.

 

[Bucky1]

I will have some things to check out now and pay attention too. I will check back with findings.

 

[Bucky1]

Ok the pump runs as it should. Hasn't made the thump for over a week now.