Depressurising the air suspension

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Catch22

Member
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13
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Norway
Hello. I am starting work on a 1999 P38 and would benefit from some experienced advice. There are several problems of course which interact. The air suspension works reasonably well, but I need to fix leaks at the valve box to prevent the car sitting down overnight. The manual says that the air system can be depressurised via the diagnostics system, but at the moment there is zero contact with that system via the external connector.

Hence my question – is there any means of manual depressurisation? Even though the system loses pressure overnight, I understand that the various pressure lines are separated by the individual control valves, so that while one might have low pressure, others might be at 150 psi. Hence I am not too keen on simply popping off the flexible pipes. Is it possible to energise the depressurisation valve manually, i.e. hot-wiring it? Any suggestions please?
 
Catch22 said:
Hello. I am starting work on a 1999 P38 and would benefit from some experienced advice. There are several problems of course which interact. The air suspension works reasonably well, but I need to fix leaks at the valve box to prevent the car sitting down overnight. The manual says that the air system can be depressurised via the diagnostics system, but at the moment there is zero contact with that system via the external connector.

Hence my question – is there any means of manual depressurisation? Even though the system loses pressure overnight, I understand that the various pressure lines are separated by the individual control valves, so that while one might have low pressure, others might be at 150 psi. Hence I am not too keen on simply popping off the flexible pipes. Is it possible to energise the depressurisation valve manually, i.e. hot-wiring it? Any suggestions please?
Click to expand...
Wear some good solid gloves and eye protection and you can pop the pipes out no problem. DO NOT try to hot wire any valve, it will burn out on 12 volts.
 
I'd get her up to wading height, open a door and switch off. Then pull the delay timer under the passenger seat, lock up and walk away for a day or so. See which corner drops.

Sometimes the tank feed gets a pinhole from an exhaust blow.
 
The only pipe that ever has 150 or so psi in it is the pipe to the tank (No 6) Other pipes will have around 60 psi in them when the suspension is inflated with no load in the boot. As Keith says wear eye protection and pull the pipes.
 
As Data says do NOT wire 12V directly to valves, but there is a safe deflate method without pulling air lines (although pulling lines is quicker)
  • Unplug connector at front of EAS housing.
  • Apply GND to pins 10 & 11, and then 12V to pins 12 & 13. This powers the driver pack.
  • Apply 12V to pins 5 & 6 to open Inlet & Exhaust valves at same time. Tank air should escape out exhaust. (Tank --> NRV2 --> NRV3 --> Exhaust)
  • When tank is empty, disconnect pin 5 to close Inlet valve
  • Apply 12V to pins 1, 2, 3, 4 & 6 to open all four corner valves & exhaust. Air bags should deflate.
Now you can pull the airlines without risk.
 
Datatek said:
Wear some good solid gloves and eye protection and you can pop the pipes out no problem. DO NOT try to hot wire any valve, it will burn out on 12 volts.
Click to expand...
OK, thanks, I will try this. By the way, what voltage does the control system operate on? Is the signal to the valves a simple applied voltage or a digital signal?
 
The signals from ECU to the EAS housing connector are all 12V on-off signals. The driver pack converts these to variable voltage pulsed waveforms to avoid solenoid overheating & damage. This is why you should never connect 12V directly to the solenoids.
 
pwood999 said:
As Data says do NOT wire 12V directly to valves, but there is a safe deflate method without pulling air lines (although pulling lines is quicker)
  • Unplug connector at front of EAS housing.
  • Apply GND to pins 10 & 11, and then 12V to pins 12 & 13. This powers the driver pack.
  • Apply 12V to pins 5 & 6 to open Inlet & Exhaust valves at same time. Tank air should escape out exhaust. (Tank --> NRV2 --> NRV3 --> Exhaust)
  • When tank is empty, disconnect pin 5 to close Inlet valve
  • Apply 12V to pins 1, 2, 3, 4 & 6 to open all four corner valves & exhaust. Air bags should deflate.
Now you can pull the airlines without risk.
Click to expand...
If he tries that and gets it wrong he will be in a world of pain. It's not necessary.
 
pwood999 said:
The signals from ECU to the EAS housing connector are all 12V on-off signals. The driver pack converts these to variable voltage pulsed waveforms to avoid solenoid overheating & damage. This is why you should never connect 12V directly to the solenoids.
Click to expand...
The driver pack uses "Pick & Hold" , a very short 12 volts to pull the solenoids followed by a 9 volt wave form viewed with a DVM.
IMG_2849.JPG
 
Very good - thank you for all the answers!
What about the collets? In case of breakage, can these be bought as separately? Are these a standard air-fitting used elsewhere than in Land Rovers? Are they used in later model Land Rovers?
 
Catch22 said:
Very good - thank you for all the answers!
What about the collets? In case of breakage, can these be bought as separately? Are these a standard air-fitting used elsewhere than in Land Rovers? Are they used in later model Land Rovers?
Click to expand...

Collets can be purchased. But you need to be really hamfisted to break them.
 
I agree on pulling the pipes, which is what I usually do !! But answered the original question just for the sake of it !!

Both EAS-Unlock and Nanocom also have this option if people want to avoid the sudden air release when pulling pipes.
 
Catch22 said:
Very good - thank you for all the answers!
What about the collets? In case of breakage, can these be bought as separately? Are these a standard air-fitting used elsewhere than in Land Rovers? Are they used in later model Land Rovers?
Click to expand...
They will pop out easy enough with the air to help. You are more likely to lose one than break it.
There are two o-rings in each that tend to stay where they need to be but check they are both sitting tidy before putting collets back in.
 
There's also the "reduce system pressure option" . . . .. unplug pump, start car, and change from Normal to High-Mode to Access as often as it will allow to use up the available air. Now when pulling the lines there will be much less pressure in the system, and less risk of collets flying out (never seen this happen though) !!
 
Just do the "pull the pipe" option. Good pair of gloves, push in the collet and go. It's a bit nerve racking at first go but stops a lot of messing around and then you know the system is empty.!
 
Bagshot said:
Just do the "pull the pipe" option. Good pair of gloves, push in the collet and go. It's a bit nerve racking at first go but stops a lot of messing around and then you know the system is empty.!
Click to expand...

It certainly beats drilling an 8mm hole in the bags and tank. :D:D
 
Very good - many thanks! Being the careful sort I will try the cycling option to reduce the pressure as much as possible before pulling the tubes.
But I am still curious about where new collets can be bought, if necessary. Do Land rover sell them for a newer model (than a P38) or are they an industry standard that I can buy from a air equipment stockist?
 
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