Recommended Hitachi Air Supply Unit (compressor) maintenance?

[twr7cx]

Both our MY12 D4's have the Hitachi Air Supply Units (compressors) fitted. Is there any recommended maintenance or servicing of these to prolong their lives? Most of the discussions from my searching really only start once faults are already occuring. It seems that some has had issues with the desiccant in the Air Dryer going off or turning to powder? Then I've read other stories about people who've done repairs on them to find that they only lasted another month or so.

[rdenyer]

Hello
So I have a 2005 Discovery 3 TDV6 - had it since new.
About a month ago I started getting "suspension faults".
With the IID tool - these were the faults

1. C1A13-64 (28) Pressure does not decrease when venting gallery - Algorithm based failure - signal plausibility failure
2. C1A20-64 (AF) Pressure increases too slow when filling reservoir - Algorithm based failure - signal plausibility failure

Finally - it became almost undrivable with almost no air available (disco 3 is a really uncomfortable drive on the bump stops !)

Some internet and forum research indicated the less likely to be the valve and more likely the desiccant canister is blocked. The filters are probably full of dust from the desiccant breaking down. Air passes in and out through the canister so the air down is probably struggling to exit.

So - fifteen years and 189,000 km, I seems I need to service the compressor - have ordered a kit from 4x4airseals.com along with a complete o-ring kit for all the solenoids.

But in the meantime - I got a tip from a fellow forum member that there are some "cheap" Hitachi compressors on eBay Air Suspension Compressor Pump For Land Rover Discovery 3 Hitachi Type LR023964 6941503307842 | eBay which I have now ordered one.

Plan is to swap out the genuine compressor with the cheap one, to get back on the road then spend my time doing a full refurbishment on the OEM compressor, then swap back . 4x4airseals.com have some great videos.

Will then also have a spare compressor.

Long story, but for your original question, 15 years with no maintenance is pretty good - maybe it could have been avoided if I serviced at 10 years and replaced desiccant, but who knows - have not seen any mention in the service manual, maybe LR thought those in heavy use would burn out the motor an be replaced, before the desiccant , went to dust.

[PerthDisco]

Hello
So I have a 2005 Discovery 3 TDV6 - had it since new.
About a month ago I started getting "suspension faults".
With the IID tool - these were the faults

1. C1A13-64 (28) Pressure does not decrease when venting gallery - Algorithm based failure - signal plausibility failure
2. C1A20-64 (AF) Pressure increases too slow when filling reservoir - Algorithm based failure - signal plausibility failure

Finally - it became almost undrivable with almost no air available (disco 3 is a really uncomfortable drive on the bump stops !)

Some internet and forum research indicated the less likely to be the valve and more likely the desiccant canister is blocked. The filters are probably full of dust from the desiccant breaking down. Air passes in and out through the canister so the air down is probably struggling to exit.

So - fifteen years and 189,000 km, I seems I need to service the compressor - have ordered a kit from 4x4airseals.com along with a complete o-ring kit for all the solenoids.

But in the meantime - I got a tip from a fellow forum member that there are some "cheap" Hitachi compressors on eBay Air Suspension Compressor Pump For Land Rover Discovery 3 Hitachi Type LR023964 6941503307842 | eBay which I have now ordered one.

Plan is to swap out the genuine compressor with the cheap one, to get back on the road then spend my time doing a full refurbishment on the OEM compressor, then swap back . 4x4airseals.com have some great videos.

Will then also have a spare compressor.

Long story, but for your original question, 15 years with no maintenance is pretty good - maybe it could have been avoided if I serviced at 10 years and replaced desiccant, but who knows - have not seen any mention in the service manual, maybe LR thought those in heavy use would burn out the motor an be replaced, before the desiccant , went to dust.

Yes ‘Hitachi Type’ is cheaper knock off.

You’ll definitely want to slot the bracket for the top bolt as that really takes the fun out of swapping them. If you can loosen it a few turns to drop it out so much easier than backing it right out. A long reach thin ratchet spanner would be good also coming up from behind the compressor along the chassis frame otherwise you have to use flex joints and socket extensions over the top of the comp which is like docking the lunar module to get it on the head of the top bolt.

Really take your time to fully disassemble and clean the unit.

You’ll do the piston seal as well.

There’s a couple of interesting orings for the hose quick connections not well explained. The new cap for the dryer takes care of those hose connections but on the other end of the comp there are two low pressure larger intake ones. You prise the movable collar out and there’s orings inside that are included in the kit.

Use needle nose pliers to push the hoses fully in then hold the collar down (screwdriver or another needle nose pliers) then pull the air hose out. A bit of crc helps.

[twr7cx]

Long story, but for your original question, 15 years with no maintenance is pretty good - maybe it could have been avoided if I serviced at 10 years and replaced desiccant, but who knows - have not seen any mention in the service manual, maybe LR thought those in heavy use would burn out the motor an be replaced, before the desiccant , went to dust.

Yes, and this is why I wonder if I should replace the desiccant and such on our second MY12 D4 that is of similar age (but slightly higher kms) to the one currently experiencing the fault to avoid a future fault appearing.

[PerthDisco]

Yes, and this is why I wonder if I should replace the desiccant and such on our second MY12 D4 that is of similar age (but slightly higher kms) to the one currently experiencing the fault to avoid a future fault appearing.

I did the desiccant and lid (the old lid had a hairline crack between the hoses as they do) only about 4-5 years ago preventatively on my MY08 and it worked trouble free till mid last year when it clearly started to need a new piston seal. I fully rebuilt a spare unit and swapped.

There’s an oring for where the dryer fits on the comp also in the basic kit that’s easy to change.

I pulled apart the old one completely there was nothing sad or wrong it just also needs a kit and clean out. Desiccant was still in good nick. WA is friendly on this stuff vs a more humid environment.

We only have a dry heat over here!

It gets very dirty and dusty so does not hurt to take covers off and get it out and exercise all the hose connections etc.

[DiscoJeffster]

I did the desiccant and lid (the old lid had a hairline crack between the hoses as they do) only about 4-5 years ago preventatively on my MY08 and it worked trouble free till mid last year when it clearly started to need a new piston seal. I fully rebuilt a spare unit and swapped.

There’s an oring for where the dryer fits on the comp also in the basic kit that’s easy to change.

I pulled apart the old one completely there was nothing sad or wrong it just also needs a kit and clean out. Desiccant was still in good nick. WA is friendly on this stuff vs a more humid environment.

We only have a dry heat over here!

It gets very dirty and dusty so does not hurt to take covers off and get it out and exercise all the hose connections etc.

I think the desiccant fails more often if you have a leak. The desiccant continuously absorbs moisture on intake as the system is always taking on air and rarely exhausting air which helps to dry the desiccant.

[PerthDisco]

I think the desiccant fails more often if you have a leak. The desiccant continuously absorbs moisture on intake as the system is always taking on air and rarely exhausting air which helps to dry the desiccant.

I was just also thinking about this. From memory the pump is blowing compressed air through the desiccant to dry it because the dirt shows on only the piston side of the filter pad that sit under the desiccant. Also that’s why the desiccant bottle lid fails because it’s under pressure? That was my memory of how it works.

The incoming fresh air is only coarsely strained through the filter that lives in behind the tail light.

[DiscoJeffster]

I was just also thinking about this. From memory the pump is blowing compressed air through the desiccant to dry it because the dirt shows on only the piston side of the filter pad that sit under the desiccant. Also that’s why the desiccant bottle lid fails because it’s under pressure? That was my memory of how it works.

The incoming fresh air is only coarsely strained through the filter that lives in behind the tail light.

The air the pump is collecting is fresh air. It doesn’t matter how it gets through the desiccant canister - it still has moisture in it. The idea is intake is wet and cleaned via desiccant and the exhaust air is dry and as it exits the desiccant canister it takes out the moisture. If your system has a leak then the balance will be lost.

[PerthDisco]

The air the pump is collecting is fresh air. It doesn’t matter how it gets through the desiccant canister - it still has moisture in it. The idea is intake is wet and cleaned via desiccant and the exhaust air is dry and as it exits the desiccant canister it takes out the moisture. If your system has a leak then the balance will be lost.

Yes but every time I start my car in the morning the compressor will turn on soon after and run for a few minutes. I therefore assumed the desiccant and lid is seeing condensate heavy compressed air every day you use the car.