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jekyllman
Member Since: 27 Dec 2020
Location: Pocatello
Posts: 42
  
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| Suspension drooping overnight ONLY with suspension fuse in |
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Ok so my suspension has slowly been drooping overnight to the point that when I wake up in the morning the top of the tire is nearly level with the bottom of the fender. It's progressed over time so I figured it was the airbags or something slowly leaking and has got worse with time.
I had swapped out the front struts only a year ago so I was going to be annoyed if it were one of those. I cleaned out the front valve block to eliminate that from the list of potential issues. I also sprayed everything I could with soapy water to try and identify the source of the leak. Couldn't find any bubbles anywhere.
I decided to pull the fuse to see which corner would drop the most. I measured all 4 wheels immediately after turning the vehicle off. The next day I went out and measured and every corner was identical to the night before. I repeated the measuring in the afternoon that same day, zero change! I have to admit I was simultaneously impressed and confused.
So here is where my question comes in: how does the suspension drop overnight WITH the fuse in but NOT when it's pulled? What mechanism is at play here? Some kind of computer issue that is erroneously letting air out? I'm considering a timelapse video to see if it slowly leaks or if it does it in stages, as if the valves are opening/closing.
Any logical thinkers out there that can break this down for me would be very appreciated!!
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 8th Sep 2022 7:47 am |
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Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10365
  
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As you say it is a control/computer/height sensor issue.
One height sensor being slightly dodgy
If you have a diagnostic tool with live values it may give clues
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| 8th Sep 2022 8:55 am |
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Flack
Member Since: 06 Sep 2006
Location: Preston Lancashire
Posts: 6235
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The system wakes up to check the heights {with the fuse in} on a regular basis when left over night parked up. If your's is dropping then you have a leak somwhere.
With the compressor not running, if it needs to level the car it will lower the other corners to try to level the car.
As Pete as said you need to get a tool on it and check live values to see what the output is.
Flack 
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| 8th Sep 2022 9:44 am |
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jekyllman
Member Since: 27 Dec 2020
Location: Pocatello
Posts: 42
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I really don't think there's a leak. There's zero drooping with the fuse out.
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| 8th Sep 2022 4:06 pm |
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BradC
Member Since: 29 Apr 2019
Location: Perth
Posts: 118
 
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What I've seen with significant temperature variation is the corners of the car move about as the temp changes. Due to static friction in the suspension, some move more than others and when it wakes up and sees one or more corners out of kilter it "adjusts". Think a gradual change in force from the airbag until it finally overcomes the static friction in the joints and "squeak/pop" it moves.
My experience has been with the car locked up in a garage, it doesn't move. With it out the front on the driveway it can be down to the stops in a few days. A combination of sun and wind causing large positional temp fluctuations seems to exacerbate the problem.
When I was chasing a valve block leak I set up a time lapse CCTV camera on the car and watched it for several days with the fuses out. I was astonished at how much it moved around as the outside temperature and conditions changed.
We have to park it outside in the elements and it frequently drops. If I leave it in my parents garage it doesn't drop.
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| 9th Sep 2022 6:04 am |
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cfcjim
Member Since: 22 Jun 2010
Location: Munich
Posts: 65
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How level is the garage?
If it is on an incline, the vehicle will keep trying to level itself.
The area where I park during the day points downhill and my car is always lower at the end of the day than when I arrived early morning.
My garage is level and overnight the suspension stays up.
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| 9th Sep 2022 6:44 am |
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munst
Member Since: 16 Sep 2020
Location: GLOS
Posts: 155
 
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The car doesn't level to 'gravity', it shouldn't keep trying to level its self on a slope unless something is moving it.
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| 9th Sep 2022 12:05 pm |
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jekyllman
Member Since: 27 Dec 2020
Location: Pocatello
Posts: 42
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BradC wrote:What I've seen with significant temperature variation is the corners of the car move about as the temp changes. Due to static friction in the suspension, some move more than others and when it wakes up and sees one or more corners out of kilter it "adjusts". Think a gradual change in force from the airbag until it finally overcomes the static friction in the joints and "squeak/pop" it moves.
My experience has been with the car locked up in a garage, it doesn't move. With it out the front on the driveway it can be down to the stops in a few days. A combination of sun and wind causing large positional temp fluctuations seems to exacerbate the problem.
When I was chasing a valve block leak I set up a time lapse CCTV camera on the car and watched it for several days with the fuses out. I was astonished at how much it moved around as the outside temperature and conditions changed.
We have to park it outside in the elements and it frequently drops. If I leave it in my parents garage it doesn't drop.
This is an interesting take. So you're saying that overnight as the temps cool off the volume of air in each airbag decreases but each individual strut will drop at slightly different times because they get "stuck" for a minute until they loose enough volume. If they're not at the same height when the car wakes up it will let air out of the opposing corner to balance.
My questions would be: doesn't the car only wake up somewhere around 6-9 hrs after being turned off? Unless it wakes up every 15 minutes to level itself, I don't see it having enough "checks" over the amount of time we're dealing with to lose the amount of height I'm seeing. Also, there would have to be some fairly sticky struts to make them resist lowering to any significant degree, no?
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| 9th Sep 2022 4:27 pm |
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BradC
Member Since: 29 Apr 2019
Location: Perth
Posts: 118
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According to the manual it's 2 hours after the ignition was switched off, then every 6 hours after that.
It's not necessarily just the struts that stick, it's also the suspension components. Ball joints, bushes, CV joints, .... all have some form of static friction. In my case, the passenger side of the car gets the morning sun and the drivers side the afternoon sun and I live in a place where the sun can be "severe".
Anyway, that was my observation after watching it over a several day period in time lapse.
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| 10th Sep 2022 2:18 am |
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jekyllman
Member Since: 27 Dec 2020
Location: Pocatello
Posts: 42
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Just an update: I did a timelapse and the droop was a consistent movement downwards; no sticking and adjusting. Still not sure why it's doing this...
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| 3rd Oct 2022 5:55 pm |
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Yankee_Rover
Member Since: 02 Jun 2021
Location: Seattle
Posts: 183
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You would want to do a timelapse with the fuse pulled, then you might see it raising spontaneously. I have observed this behavior myself, it is more prevalent in the fall and spring when the temperatures fluctuate more greatly.
Your other option is to test your ride height sensors as was previously suggested. 2008 LR3 HSE, 4.4L V8
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| 4th Oct 2022 2:24 pm |
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