Hey Guys,

I have an 08 LR3 with a rod mod and oversize tires. My truck is still using the OEM Hitachi compressor, but it bleeds air from the suspension at about an inch per day. When I drive it everyday it's not so much of a problem, but leaving it for longer periods of time really causes issues for me.

About a year ago past year I've replaced the drier (which cleared my yellow air suspension fault that had popped up) and prolonged the life of my Hitachi a bit longer.

To diagnose the leak, I pulled my fuses and let the car sit for a few days. The front pretty much dropped at an equal rate while the rear stayed up. This lead me to believe that I had an issue with my front valve block. I replaced it. But unfortunately still have the leak. (Looking back on this, I'm not sure if I pulled all the correct fuses.)

Which leads me to my current problem. Recently, I left my truck for 8 days without driving it. I came back to it and the LR3 was lower than I had ever seen and fully on its bump stops, leaving me basically no clearance at all with my 275/75/18s. I got in to turn on the ignition and got a red suspension fault, as well as a fault telling me my self-turning headlights were disabled. The car was pretty much un-driveable, so I had it towed to Expedition Autoworks here in Minneapolis. Once they put it on the lift and dropped the tires down a bit, the compressor fired back up and raised the truck to normal levels. All the faults went away.

To diagnose the leak they left my driver door open overnight in the shop. They claim that the truck didn't drop at all. Their guess is that my exhaust valve is leaking on the expansion tank and that I'll need to get the new AMK unit. Does this sound right? Does it mean I need a new compressor? Would it address my slow leak?

Appreciate the help! And apologies for the long post!

-Chris

 

I don't know that I'd want to replace the compressor based on "their guess." I advise you to get the faults/codes read so that you know what is going on. It would also be good to watch the live values of the gallery pressure as the compressor fills it. There are target pressures it tries to hit, then exhausts. If it can't fill the tank or does it very slowly, it can be either a dying compressor or a leak at the tank (valve).

 

I had the fault codes read a while back and did get one that mentioned that the compressor was slow to fill, I forget the specific code.

Dumb question, but does the tank come as part of the compressor unit? Or is that a separate part?

Thanks

 

C1A20 - Pressure increase too slow when filling reservoir.

I just went through this with my 2008 LR3. I ended up replacing the compressor with an AMK (after a drier and piston rebuild on the original Hitachi.

The compressor is separate from the tank.

 

Thanks for the response. I guess I need to get back on the phone with the guys in the shop tomorrow morning and ask them directly whether I need to replace the compressor, or the tank, or both. I'm still not fully comprehending how it leaks only when the compressor is active. Maybe I'll ask them about that too.

 

You (or they) may be mixing up terms a bit here. There is no exhaust valve on the "tank". The tank or "reservoir" has one line that feeds it from the reservoir valve block (which is located with the compressor). The reservoir valve block has a valve in it which simply opens and closes to allow air into or out of the reservoir (through that single line). Basically, all it does is equalize the pressure in the system. The compressor feeds air into the reservoir valve block, which then distributes it unchecked (i.e. no valves) to the front valve block and rear valve block. It also distributes the air to the reservoir through a reservoir check valve.

The reservoir check valve may open initially when shutting the car off to release some pressure in the reservoir by allowing air to exhaust from the entire system. This is done to bring the pressure down in order to facilitate the compressor starting the next time you start your car.

After that initial release, I don't believe the reservoir check valve should ever open while your engine is off.

Sooo... that leads me to the point. You say you got the "slow to fill" message and the red warning light. This could be for one of two reasons:
1. If there was no air in the system, you might get this warning light just because the compressor will be running a very long time to fill the reservoir from zero pressure.
2. You could get the warning if there is a leak in the compressor, lines, or reservoir valve block/valve. This means that the compressor would be humming along, trying to just top the reservoir off, but only a little bit of the air being compressed would make it to the reservoir... the rest would get leaked.

In scenario 1, your reservoir or reservoir valve would be leaking. In scenario 2, your issue might be very similar to what Airstream345 just posted in other threads... a crack in the dryer cap (though let's just say anywhere in the compressor)

When you say you replaced the dryer, did you purchase the replacement unit from Land Rover or did you refresh the desiccant and/or filters only?

 

To answer this question: You would not be leaking only when the compressor is active. You would be leaking from main lines all of the time. However, keep in mind that the reservoir and each shock are all independently isolated. Therefore, if your valves are all sealing correctly, then you may have zero pressure "in the system", but still have pressure in each shock and pressure in the reservoir because they're isolated. However, when you turn the car on and try to equalize pressure and fill the shocks up from any self-leveling that has been done while the car was off, it may throw a fault because the system tries to equalize. This means that the compressor will try to bring the main lines up to pressure first (there is a pressure sensor it uses in the reservoir valve block). If it can't do this (or can't do it quickly enough), it will throw an error code. Hope this makes some sense.

 

This is all great info...this is a highly knowledgeable community!

...that said, I bet a dollar to a donut that it's the compressor. It usually is.

 

Very much appreciate all the help guys.

They did another "door test" last night and the truck had zero drop. He's certain it's the compressor unit. He said he's only seen a couple expansion tanks fail and it was only ever due to corrosion (midwestern winters).

I went ahead and ordered a new AMK unit from Lucky8. It was $808, about $350 cheaper than the dealer's price. The labor will be $300.

Hopefully, this will end my issues with my suspension for a while. Thanks again guys.

Next up: 90k service. Leaky right front axle seal. Cracking serpentine belt. Transmission/diff fluid flush. Spark plugs. $$$$$$$

 

90k is a biggie....all those things are needed. Get past this and you should be alright for a while.