Thread: Air off Kit

Dis you edit it? Or am I having another seniors moment?

A senior moment of course

Originally Posted by KOOS BEST

Hi , pse inform me , with this "air in kit" can you pump up the suspension with an auxillary compressor if the onboard one packs up?
If so how do you do it ?
Regards
Koos

How well pushing air back into the tank works as far as getting the 3 to rise back up depends upon what failed in the first place, hence the yes, maybe response.

On a good day when all is well, a full air tank sits at about 220 psig (14 - 15 bar). What is interesting is that the air springs run somewhere between 100 psig (7 bar) and 150 psig (10 bar), just like on the heavy haul trucks.

As per the previous post, shop air might be 150 psig max so in the real world, one would never be able to find 200 psig, (14 bar), air anywhere and that is in my mind, the basic design problem of the 3 air system. If LR had just decided to put a second air tank on the other side and run the system at about 10 bar like the heavy haulers, they would have had a choice of tried and tested compressor designs to choose from - as it is, they are still trying to invent one that lasts.

Anyway, the choice of air source is yours - could be on board as there are a few that make 200 psig, (VAIR 480C), however one only needs maybe 10 bar available to get the 3 to rise and there are lots of compressors that do that. An oil free compressor would be desireable - shop air is generally not that but the ARB and VAIR portables are oil free. Less pressure would work as well to at least get it off the stops so that you can drive.

Your problems are not automatically solved when the air tank is full however. The question still remains as to why is the 3 on the stops. Is it simple air compressor failure or something to do with the computer or the wires / sensors?

Assume first it is just a failed air compressor. If so, the system does not care where the air comes from, only that there is air, so with luck, the 3 will rise once air is put back in the tank.

I say with luck as there are various check routines the 3 goes thru upon startup to see if all is well and it would eventually figure out the compressor was not working. Eventually means within a minute of engine startup probably.

There is another senario - the compressor is working fine. In this case the air tank would have max air pressure and all the Schrader valve is there for is so you can put an air pressure gauge on it and it will show 14 bar or so. You can then assume the problem is controls related and not the compressor so the air in Schrader valve will not do you much good.

This is where pulling fuses can help. I found that even with a control failure but with a good compresssor and full air tank, quite often the 3 will start to raise upon startup and then once it goes thru the check routines, vents the springs to atmosphere and down you go.

There is a fuse F35P behind the inside lower glove box that feeds power to the control system and two out in the engine compartment fuse box, F3E and F26E that can be pulled to disable the release air valves. Pulling the fuses however is tricky as you need them to get the system to rise, but they must later be pulled prior to the air release signal. My link to Disco3 below has more on that, but there is no easy answer.

Back now to the first scenario where it was only the air compressor that failed. Once the 3 goes back up, you should still pull the fuses as that will stop the 3 from deciding later on to release the air from the springs and you are back where you started - on the stops.

Incidently CaverD3 is your guy I regard as the expert on the air system and it was from him I got the idea of the air in mod.

DISCO3.CO.UK Photo Gallery - LR3 Air Suspension fuse 35P ECU Manual Shut Off Switch

How did you depressurise the system before putting the fitting in?

Th original tank bung has a flat side and seals with an 'O' ring. Slowly undo until air escapes when it stops turn some more again.
Don't get in the way of the bung when undoing incase you go too far. a brass bung with 210 psi behind it is gunna hurt.

The Land Rover Engineers are smarter than you would think it turns out.

Depressurizing the air tank is safer and easier than one would first imagine.

First, do not get under the vehicle - the system may dump and drop to the stops. It is not supposed to, but it might for who knows why. I had it happen once as I was walking away from the 3 for absolutely no reason and it is scary.

I lowered the 3 to the access height and fortunately you can get at the bung on the front end of the air tank just by laying along side the 3 and blindly fumbling a 27 mm box end wrench or socket around the bung by feel.

The threads of the factory bung have a line cut vertically in the threads that allows the air to escape slowly with just a bit of undoing. Pretty soon the bung is just finger tight and all the air has escaped.

This is in part because the bung uses a real good sort of rubber O ring recessed seal design and does not rely on the threads for the air seal.

As such, sealing of my new adapter bung to the tank threads was the major problem I had. I did not want to use teflon tape as I never know where the stuff goes so I used teflon pipe dope, but very sparingly. The washer type seal that I did purchase really did not work very well - made a nice buffer between the metal of the bung and the air tank, but it was the pipe dope that ultimately provided the seal.

I did get a seal but it took me a couple of tries with that bubble "soap" liquid leak finder fluid as an integral part of my quality assurance program.

Probably the correct way to do the mod is to first purchase a new bung from Land Rover and then tap it for the Schrader valve or I suppose tap the one you remove. Then you will have the best of all worlds.

You also may as well get some of that leak detection fluid before you start as an air leak is really the only thing that can go wrong.

When I put all back together, I just started the engine back up and the compressor started up and eventually the tank filled back up with air. I seem to recall the compressor stopped a couple of times and rested, but nothing special.

I also made up a 16 bar pressure gauge assembly with a rubber hose about a foot long on it so I can check tank pressure now whenever I wish just by laying along the 3 and fumbling around.

Testing for leaks is easy just a 50/50 mix of dishwash detergent and water sprayed on the joint, leaks will show as bubbles very quickly.
I used teflon tape but the thick yellow gas one.