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Air Suspension - only front right sagging overnight

25K views 10 replies 6 participants last post by  Necropolis 
#1 ·
2011 RR SC with under 60k miles. We’ve noticed when the truck sits overnight, the front right is sagging fairly considerably by morning. Upon startup, it lifts back up quickly and the truck is perfectly level and then drives fine. I’ve done a cursory review of the air line and front valve block spraying with soapy water and cannot find a leak. We also had a LR tech who is a friend test the seal on the front right air strut (Arnott replacement from 6 months ago) and it seemed fine too. It was suggested that it could be the compressor getting old, but if the compressor were going out or had a leak internally would you always see just the front right sag overnight (roughly 2.5” measured from
Center cap. The left rear actually goes up a touch and the other corners only measure 0.5” lower). Is this definitely an air leak somewhere or could it be a height sensor or something similar that causes that corner to drop when the truck attempts to level itself after sitting for awhile?
 
#2 ·
Compressor wearing out would impact the entire system. A height sensor would not cause a drop. If your Arnott is only 6 months old then it is not one of their dreaded rebuilt units and "should" not be failing in any way. The left rear rising is only your rig "pivoting" on the front left and right rear which are stationary. It is perfectly normal to have the opposing corner raise when one corner drops.

I can't see how this can not be a leak. If the Arnott is not leaking the only other option I can think of is venting at the valve block, but you have soaped that up. The trouble with finding leaks like this is that they are so small/slow.
 
#4 ·
The left rear rising is only your rig "pivoting" on the front left and right rear which are stationary. It is perfectly normal to have the opposing corner raise when one corner drops.
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hmmmmmm....I concur

Other places to look - the brass hose connector at the top will leak very slowly (around the o-ring)
The height that your rover is left at when you return home/other is usually
is the only place it would be leaking at. So it's difficult to replicate this by
just pressurizing the bag. The crease in the bag changes at different heights and might not
leak on your highest offroad height.
Put it up on off road height to see if it still leaks over night. If it remains at this height, then the valve block, or possible pump leaks are eliminated.
Try access height as well - a bit more difficult to see this height level change though.
My bet is on your bag...very classic symptom you've described thus far...
 
#3 ·
Thanks for your feedback. Yea, I've soaped up the front valve block really good and didn't notice anything while the vehicle was running, but maybe i'll go back and try again while putting it in off road mode so the PSI is higher. Is there anywhere else besides the air line from the front valve block to the top of the air strut, or the air strut itself that i could look that would cause just the front right to sag?
 
#5 ·
...didn't notice anything while the vehicle was running...
Uhm... you do NOT check for leaks while the car is running. the entire issue is that it is dropping overnight... you do not leave your rig running over night... do you? :mrgreen:

Check for leaks while the Rover is running means the compressor is constantly refilling the air in the bladder if there is a measurable leak. Any cracks, although not likely this soon, will remain sealed/closed. If it is an ORing issue the airline will always be under pressure and pulling up from the fitting. With the engine off there will be no pressure and if the fitting is not tight you should quickly see and hear bubbles where the line is not properly seated.
 
#6 ·
You guys are the best. Cranked it up to off road height in our flat garage, measurements turned out a bit wonky (LF 19.75, LR 19.5, RF 21, RR 21), but think I found the leak with the truck turned off. Appears to be at the base of the top brass hose connector on the problematic front right air strut as shown in the video below. I'll do some searching around, but what's the best way to go about fixing this? New brass connector and o-ring?
 
#7 ·
Upon further investigation, i'm not sure this part can easily be replaced. It appears to be the base of brass extension from the Arnott air strut which is failing.. I've emailed Arnott to see if anything can be done or if the entire strut needs to be removed and replaced with an exchange under warranty.
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#8 ·
I have a similar situation - brand new ARNOT struts and bags installed by me about 2-3 months ago. when I wake the truck up in the morning, the back drops a few inches to adjust for what was lost in the front. I recall installing the brass connector when I received the struts so they must be replaceable, though the struts may have to come out to do so.

I'm curious how ARNOT responds to your inquest.
 
#9 ·
They said it's a leak from the "pressure or alligator valve" on the air strut and no way to repair or replace a small part. The entire air strut needs to be removed and returned for warranty exchange (just bought a new one and will get credit back after returning the failed part). Not sure if they'll reimburse for labor expense but will inquire about that as well. Frustrating to say the least as the one we installed is only 6 months old from manufacture date.
 
#10 ·
Just a heads up. From my experience i've encountered this same issue three times. When i first purchased my range the front right was leaking due to the valve block sticking on the inside. You wouldnt see this from soap and water from the exterior. If you search there is a diy on how to take it apart and clean. When i dismanteled the block there was a noticable amount of white dust on the inside, think it came from the silca from the old compressor. 2nd time about 20k miles later, the original owner never changed any of the suspension components and the bag coil had a noticable leak. Changed the unit and it was gone. 3rd time was similiar to yours, the brass fitting was seeping air. Arnott actually includes two brass fittngs in the box with one shock. I didnt call them i just replaced the fitting & cut the hose back about 10-15mm. Put everything back together and 10k miles later still no issues.
 
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