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Air Susp. Compressor comes on at startup after car sits overnight, but no drop in height.

Dec 26, 2018
574
464
TX
Hey folks,

Over the last week or so, I've noticed that my air compressor comes on every time I turn the car on after it's been sitting overnight. Obviously there's a leak somewhere.

The air shocks maintain pressure, and the car doesn't drop in height - so I'm curious if the leak is between the tank and the compressor.....or maybe #3 or #4 in the diagram below (not really sure of their function).

Curious if anyone else has experienced a leak *before* the valve block that controls air distribution to the struts, and where it ended up being!



1619660058253.png
 

scaesare

Well-Known Member
Mar 14, 2013
8,534
14,727
NoVA
What vintage car? Power brakes on earlier cars also also used a pump and it's common for those to trigger at power up. Mine has done it since new.
 
Dec 26, 2018
574
464
TX
What vintage car? Power brakes on earlier cars also also used a pump and it's common for those to trigger at power up. Mine has done it since new.

July 2016 P90D. I'm 99% sure this is the air compressor pump, unless the brake booster pump sounds exactly the same.
 

Lasttoy

Active Member
Mar 24, 2017
1,616
852
St Augustine, Fl
How did u hear it??? I had my trunk out for months fixing my liquid system. I heard so many sounds when I worked on it. There's always buzzing or humming. It was fun, touch each thing to see which was working. My pump 2 was bad. U could have an air leak, good luck on finding it if struts stay up.
 
Dec 26, 2018
574
464
TX
How did u hear it??? I had my trunk out for months fixing my liquid system. I heard so many sounds when I worked on it. There's always buzzing or humming. It was fun, touch each thing to see which was working. My pump 2 was bad. U could have an air leak, good luck on finding it if struts stay up.

i can hear the air compressor from the cabin. Heard it a lot when I was installing my lowering links because it required moving up and down and fine tuning.
The nice thing is, since the struts stay up I know the leak must be before the distribution block, and that only leaves one or two hoses.
 

Gtech

Member
Dec 4, 2016
534
647
Netherlands, Berkel en Rodenrijs
Hey folks,

Over the last week or so, I've noticed that my air compressor comes on every time I turn the car on after it's been sitting overnight. Obviously there's a leak somewhere.

The air shocks maintain pressure, and the car doesn't drop in height - so I'm curious if the leak is between the tank and the compressor.....or maybe #3 or #4 in the diagram below (not really sure of their function).

Curious if anyone else has experienced a leak *before* the valve block that controls air distribution to the struts, and where it ended up being!

Seems logic to me that if your shocks keep height the lines from the valve block to the air shocks are indeed not the issue.

You could check this T fitting for leakage:


If not, you can use water with dish soap to check for air bubbles under the frunk, maybe an air hose is rubbing against something.

Good luck and keep us updated.
 
Dec 26, 2018
574
464
TX
Seems logic to me that if your shocks keep height the lines from the valve block to the air shocks are indeed not the issue.

You could check this T fitting for leakage:


If not, you can use water with dish soap to check for air bubbles under the frunk, maybe an air hose is rubbing against something.

Good luck and keep us updated.

I don't actually have that schrader valve on a tee - all I can see on the front crossmember is a loom of three air tubes - black one to the tank, yellow to the passenger front strut, blue to the driver front strut.
 

Doanster1

Active Member
Feb 14, 2018
1,030
558
Oregon
I don't actually have that schrader valve on a tee - all I can see on the front crossmember is a loom of three air tubes - black one to the tank, yellow to the passenger front strut, blue to the driver front strut.
Yep, only the older cars had the Schrader valve on a tee. Now the valve is mounted directly on the reserve air tank. Check for leaks there.
 
Dec 26, 2018
574
464
TX
I FOUND IT! Double check me, but I think this is my slow leak. Connection is from compressor to tank. All others formed no bubbles when sprayed with soap+water.


I may just have Mobile come out to cut some material off and re-seal that connector...I could depressurize the system via the schrader valve, but I don't want to risk it coming back on while I'm working or whatnot. They can disable everything via Toolbox and take care of it easily.
 

Doanster1

Active Member
Feb 14, 2018
1,030
558
Oregon
I FOUND IT! Double check me, but I think this is my slow leak. Connection is from compressor to tank. All others formed no bubbles when sprayed with soap+water.


I may just have Mobile come out to cut some material off and re-seal that connector...I could depressurize the system via the schrader valve, but I don't want to risk it coming back on while I'm working or whatnot. They can disable everything via Toolbox and take care of it easily.
Nice job. You could just power the car down while you try to tighten/re-seal it yourself? Even if the compressor kicked on, the noise might startle you, but no real danger.
 
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Dec 26, 2018
574
464
TX
Nice job. You could just power the car down while you try to tighten/re-seal it yourself? Even if the compressor kicked on, the noise might startle you, but no real danger.

Is that connection just a push-to-seal with a thread? As in, I could just depressurize, unscrew, cut the line, push new length through, and screw it back in?
 

Doanster1

Active Member
Feb 14, 2018
1,030
558
Oregon
Is that connection just a push-to-seal with a thread? As in, I could just depressurize, unscrew, cut the line, push new length through, and screw it back in?
That I’m not sure about. Fittings like that usually have “barbs”, but I’d think you’d still need some sort of sealant, whether Tef-tape, silicone, putty, etc.
You could go shade tree and squirt silicone/super/gorilla glue around the fitting and see if that’ll work? :)
 

2101Guy

Active Member
Jan 6, 2020
2,050
2,546
USA
ive found that (most?) air fittings as well as fittings associated with high pressure systems (like old school mercedes hydraulic suspensions) have to be on perfectly to ensure a perfect seal. The right amount of torque (but dont strip) and at the PERFECT head on angle. This might be your case.

I once did some work on an air setup and a separate job on hydraulic suspension. Fittings seemed to be perfect. Didnt feel cross threaded at all. Wasnt until I broke out the reading glasses and BRIGHT light and threaded slowly and carefully did I resolve the issues both times. Its possible to cross thread without actually damaging the threads much at all and it will feel "ok". But in reality, not a perfect seal.
 
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Reactions: outdoors

VaztheDad

Member
Apr 23, 2019
116
67
Nashville, TN
I FOUND IT! Double check me, but I think this is my slow leak. Connection is from compressor to tank. All others formed no bubbles when sprayed with soap+water.

Where exactly is that? My rear suspension typically runs for a few seconds after startup and I'd like to check this as well.

Is this behind the wheel? Accessible with the wheel still on?
 
Dec 26, 2018
574
464
TX
Where exactly is that? My rear suspension typically runs for a few seconds after startup and I'd like to check this as well.

Is this behind the wheel? Accessible with the wheel still on?
What do you mean when you say your rear suspension “runs” for a few seconds after startup?
 

Jillmark99

Member
Feb 1, 2019
243
96
Ontario
That I’m not sure about. Fittings like that usually have “barbs”, but I’d think you’d still need some sort of sealant, whether Tef-tape, silicone, putty, etc.
You could go shade tree and squirt silicone/super/gorilla glue around the fitting and see if that’ll work? :)
Air suspension fittings are compression fittings. Do NOT use any sort of sealant or t-tape on it as suggested above. There is a little furrow inside that compresses and provides a seal. Release pressure from the system. Remove the connector (compression nut). Assuming you have an extra inch or so of hose, cut off the end of the hose that’s damaged/leaking. Remove the furrow from inside the compression nut and discard the small piece of damaged hose. Slide end of hose through the compression nut, slide furrow onto end of hose, connect compression nut and tighten. Pressurize system and check for leaks.
If all good reassemble whatever you took apart to access the fittings. It’s a simple fix. Enjoy.
 

BostonBurley

Member
Jan 13, 2021
138
54
South Pas
I’m having the identical problem on a 2012. When I start the car it runs and runs. If I restart the mcu, it doesn’t do it any longer. It’s done this three times in the past two weeks.
mom guessing I do have a leak similar to OP bc my car does not raise whatsoever while it runs.
 

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