Another observation... lot of black oily gunk when you release the "water" drain from the front pressure tank. Engine oil I presume from worn compressor rings???

Mammoth should be on the money with the 4 air tanks. There will be a valve mounted near the tanks with 3 or 4 sort of bumps on it. Follow the airline from the compressor to the air tanks. The tank this one goes into is the wet tank. The airline out of the wet tank will go to the valve with the 3 or 4 bumps on it and that valve will have airlines going out of it to the other air tanks. That valve distributes the air to the tanks. When you build up air one needle will move untill it gets to about 60 psi, then the other will start to move till it gets to about 60 psi, then both of them will move together. It acts a bit like a hold back valve in that it won't let air through to the next tank untill there is enough pressure in the first tank. If you need to buy air valves or a bit of advice on the air system, try Air Brake Services (ABS Trailquip) on Beatty rd at Archerfeild. They have a good range of non genuine valves that are pretty cheap and if you get the right bloke there they can probobly help with a bit diagnosing over the phone.

just for what it's worth, trackhappy noted in his first post a few issues with the crane and no PTO?...

could this be something lashed up from an 8x4 prime mover, or truck and dog?... hence the problems with supply air, brom brake, etc

feel free to cut me down as well :-/ :-/

Thanks Detective, I would never cut you down or anybody else for that matter. I respect and appreciate everybody that has the generosity to post their opinions and experience here to try to help. If there is any suggestion that I have cut anybody down it is purely unintentional and I sincerely apologise.

As for the truck, the body and crane are definitely not original. The brackets don't line up with the marks on the chassis and the mounts are VERY poor. The whole body is currently held on only by 6 1/2" bolts in fact, and you can't even easily fill the fuel tank as the filler is right on top of the tank under the tray with ony 4" clearance - wonder how long it would take to fill that tank dribbling fuel in sideways???. It is a long chassis - tray is 7M long. "They" have welded 18" odd of extra main chassis rail on the back which comes right to the back of the tray, and there is nearly a metre of gap between the front of the tray and the back of the cab, where the crane was.

Plan is to get it registered as-is then take it to a body place and have them move the tray forward, mount it properly, cut the dodgy rail additions off make it a beaver tail and add ramps. My job is to fix everything I can befoe it goes over the pits for its inspection and hopefully registration.

MrsMacPaul - Deck height is 1.25 approx and excavator is less than 3 M when the boom is stowed so height should be ok I gather.

I don't have a place to post pictures, but here are some from the auction site while they are still up there:

www.manheim.com.au/trucks-machinery/Item...D=000000000003453243

BigCam - That part seems at least to be working. Pressure builds up in one gauge until just after the red line, then the other builds until both are well into the green. They don't seem to lose any sitting which is good (Only loss is when I start fiddling) and the charging process at idle is pretty quick. You can just see the three tanks in the photo, not sure where a fourth would be unless it is very small but will go on a hunt in the weekend.

Hava a look at the bottom tank, quite a lot of truck tanks are split so it looks like 1 but there is 2. Truck may only have 3 air tanks though, wet and then one for each circuit. They normally have an accesories circuit though as well that won't get air untill the rest of the system has 75 psi.

Hava a look at the bottom tank, quite a lot of truck tanks are split so it looks like 1 but there is 2. Truck may only have 3 air tanks though, wet and then one for each circuit. They normally have an accesories circuit though as well that won't get air untill the rest of the system has 75 psi.

Count the drain valves ... that'll tell you how many tanks (or compartments)

Not going to let you off lightly with the pictures, it only takes about 5 minutes to set up a photobucket account like the rest of us.
Or you can right click on the picture, go properties and copy and paste the url inbtween the img code icons, which is the middle one when you are writing your post.

g'day Trackhappy .. i didn't quite word that last bit properly and no need for any apologies at all

keep toiling away...you'll get there....cheers