Hydrovane 90D (Perkins 108 engine)

[NevB]

Hello to all,
Does anybody know how to make the compressor function properly? Here's a bit of it's history, it was given to a friend as faulty because the engine would run ok whilst the pressure release lever was held up but would stall when the lever was lowered. He has the manual with it so after swatting up I removed the adjusting screw and servo piston assy. As I was removing it a gentle tap was required to engage the removal tool (home-made) with the adjusting rod cup, this is in direct contact with the spring, and there was a slight 'ping' which indicated that some had just released itself under spring pressure. I removed all of the items except for the servo sleeve, it would only move a couple of inches before binding in the casting so I put it back in place. After checking the piston was free to move in the servo sleeve I reassembled the unit, filled her with oil and she put out full air pressure and flow. However, the engine was revving away because the governor was not working and one of the oil cooler pipes was ruptured so a new one was fitted.
Started her up again, very little pressure and still revving away. I took the unit end cap off to check vacuum valve and the two others in there (unloader valves I think) and all looked fine. Reassembled and it is still way down on pressure and flow. CAN ANYBODY POINT ME IN THE RIGHT DIRECTION PLEASE?

[martyn williams]

A common fault with these was the pressure adjusting scew would work loose,run back and reduce pressure.Left side of air end.its only a small screw.
Are you using the correct grade of oil ? a 30 sae is best
Is the governor stuck,remove pipe and give it a squirt of WD40.
Open vent cock,or open the air cock fully open.Then close it back slowly.One thing I noticed with these machines.With the cock fully open it seems to be down on pressure.But its delivering it 76CFM of air.It could be an unloader valve stuck.Inlet air filter blocked.or separators blocked.
I will have a bit more time on Friday.If its a compressor that has overheated the vanes stick and the oil will be dark brown.
Martyn

Mine shown in photo has done 300 hours since I overhauled it,great compressor for running my air tools. Its a fairly old machine and has twin fuel tanks.The newer ones had plastic tanks that leaked around the pipe fittings.

[NevB]

Thanks for the info Martyn, I assume the adjusting screw you refer to is the one which is part of the servo assy.
The governor is full of oil and piston is free but there doesn't appear to be any suction at the vacuum pipe.
We used 46 grade hydraulic oil, maybe 30 would be better. When my mate got it there was no oil on the dipstick because of the burst pipe so not able to say what colour it was but overheating could be an issue.
I will try running it momentarily without air filter although it does look ok.

Nev.

[martyn williams]

The screw is to the left of the compressor oil filler neck.46 grade it too thick.Flush out and refill with Shell rotella SX 30 or similar.
I have a book on this machine somewhere.
There is a service kit on ebay listed under Hydrovane compressors. The kits have orings filters etc.If the machine has run dry the vanes may be damaged by over heating but these compressors are pretty robust.
Good luck
Martyn