Thread: OBA for air suspension?

Originally Posted by ytt105

I've got a 1993 Range Rover with original air suspension. 270,000kms and 14 years, not bad for a 'troublesome new fangled suspension'.

However, the compressor is starting to take a little bit longer to pump up these days. Obviously, its getting a bit long in the tooth.

I know I can rebuild it, and this is my first option, but I've started to think about adding another air-con compressor plumbed into the suspension circuit.

Anyone think of any problems? I'm a bit worried about water/oil in the system.

It is easy enough to fit seperators in for water and oil, if you have a look in any workshop / factory that has compressed air running round/ plumbed in - you will see water oil seperators - they come in vairous shapes and sizes, and as long as you have a place where you can fit it, normally at the lowest point on the system you should be fine.

Plus if you get the air intake from the engine bay, where it's hot, most of the moisture would have been 'boiled' off anyway. .......but you would still need the seperators for the oil.

I played around with one on a truck once, and had two seperators, one of which was just after the discharge, to collect oil, and it had a purge line/equaliser that had a solenoid so when the system wasn't running, any oil collected in the seperator was fed back to the compressor.

Whilst ac compressors do the job well, they are prone to kick out the oil, and if you run dry they will bugger up quite quickly, so this return line/soleoid set-up just about solved this. ......but still has to add about 10 mm every 6 months or so due to oil getting past the first seperator and into the 2nd - which was dumped.

Whatever you do, do not uses PAG, AB or Polyolester type compressor oils in this 'endless air' type setup. These oils are very hygroscopic, and as they absorb more and more moisture you and up at a point where the oil will emulsify, and turn into a horrid gooo, with zero lubricity and that will root a compressor quicker than you can say jack robinson.

Either use a good quality refrigerant grade mineral oil (suniso 4gs ) or a 4th generation synthetic from the poly alpha olafin (PAO for short) these are virtually none hygroscopic. Somebody like Actrol will carry a PAO oil in stock.

When in use as an ac compressor they would normally use a 42 - 68 centistroke oil - but this is diluted by refrigerant, so with air where there is no dilution you can drop down to a 32 centistroke oil if you want - you don't gain anything - but it's an option.