Thanks to the workshop manual, I know where the compressor is located and how to R&R it, but there's a part that I need clarification on:

Depressurize using the T4

Pressurize using the T4

Does this part make an air compressor R&R a, "Dealer ONLY" event? If not, what does the T4 do that we can't do as DIYers?

 

I would risk an opinion that this is a dealer safety related instruction. In the US they have to contend with workman's comp insurance claims, and I am sure many other countries have similar laws and agencies that do OSHA-like things. Would seem that with battery disconnected, slowly opening an air fitting and allowing it to bleed off would be prudent. Now whether the fittings can do this I don't know. As for re-pressurize, would think power it up and system should handle that, after all, it is air.

Reason for safety, compressed air can move things a lot quicker than you might think. Eye protection very important.

The Rover manuals seem to tell you to disconnect battery many times, and while we suspect that it is to run up the task count and billable time, it may also be related to safety of dropping a wrench on live parts, or a village idiot starting vehicle while another team member has close personal contact with soon to be moving parts.

 

You are correct to be concerned about what happens when you remove the compressor. In theory, if all works as it should, not much.

My question has always been how many spare fingers do I have? So far the answer has been none as I like the ten I was born with.

What I am getting at is that if you notice, at a Land Rover dealer, the vehicle is always on a frame hoist and the wheels hang down. Since I do not have a frame hoist but am instead under my 3, then I use four nominal six ton axle jacks, but they are as I use them, frame jacks. I lift the 3 up just enough with my trolley jack so that the axle jacks carry the main vehicle weight and there is very little load on the tyres/wheels. This is so if one of the air springs deflates, it will not matter where my fingers are.

The reason one disconnects the battery is so the auto level program does not play out and try to drop the 3 on you - and do not trust that bit about leaving a door open inhibits lowering. Maybe it does on the Queen's LR but not on mine.

Yes, while the LR instructions say de-pressure the system, in reality one can pretty much remove the air compressor without doing so assuming you have the frame jacks under etc.

In theory, the front and rear block valves fail closed and lock the air into the air springs; the centre one kind of locks the air tank air in as well. In practice, if you have a circa 2005 /06 LR3, then there is a bung in the front end of the tank that you can undo and let the air out. See my album as below re the air tank mod.

Below is a link to a number of albums within some of which are files related to the air system - block diagrams, wiring diagrams, etc. You might want to study some of them a bit more before you remove the compressor. After you have done it once, it is relatively easy, but remember, your 3 is no Chev - there can be lots of surprises.

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If your installing a new factory compressor, you are supposed to update the software too. Its also a good practice to hang a new relay as well.

 

...does that mean that a compressor R&R is a dealer-only fix because of the software update (I'm assuming you mean that $125 deal they do that takes 20 minutes)

 

Below is the link to my file on changing out the air compressor relay and provides some info re the air compressor software update.

I would say that you could replace both the compressor the relay yourself, and in theory pay the Land Rover dealer to do the software update. In practice, the dealer may not even know about the update or claim he can only do the update if he does the compressor install.

DISCO3.CO.UK Photo Gallery - LR3 Air Suspension fuse 35P ECU Manual Shut Off Switch/Underhood Fuse and Relay Box drawing

If an independent or yourself has access to a Faultmate or something similar plus the software, then that is an alternative to the LR dealer and his T4 unit.

As noted in the referenced file, among other changes, the update reduces the air tank operating pressure from a nominal 240 psig to about 210 psig and this presumably extends the life of the air compressor.

 

That is correct and is what I used to do before I got properly equipped to work on Land Rovers. We would do the compressors at the shop and off to the dealer for the software.

20 minutes is probably a fair evaluation, but you paying for more than just the tech's time. When you consider what it costs to be able to do such a task, $125 is a bargain.