Noise will be the ABS pump as you suspect. It will try to pressurise the system and stop eventually (about 30-40 seconds) but the rear brakes are on the power circit so as soon as you touch the brake pedal, it'll blast all the fluid out of the hose (or more likely pipe) that has just burst. There's two short metal pipes that lurk at the back that rot through. Easy enough to make up a new one in Kunifer tubing but you will need a crows foot spanner to get to the top union. To bleed it, just turn the ignition on and get a glamorous assistant (or a bit of broom handle wedged between the pedal and the seat if you don't have one) to press the pedal.

As the pump has run out of fluid, there's a bleed nipple on the pump itself that may need cracking open very briefly. Do NOT allow anyone to drive it as it is, it'll empty the reservoir in a matter of seconds as soon as anyone puts their foot on the brake,

I also would agree that chances are a pipe has probably rusted through and is causing your leak.

I don't think it's quite as dire as Gilbertd mentions about it emptying itself in seconds (I also would NOT advise driving it far until fixed though!)... as the rear brakes, whilst on the power circuit, yes, don't get the full pressure that the front calipers get from the power circuit. The rear brakes have a pressure reducing valve which is external to the modulator block (hides under the coolant tank) which then creates the slight brake bias towards the front.

It will still drain the reservoir fairly quick - but not as fast as if it was a front line which failed, as they DO have full brake pressure going to them!

Thank you both Gilbert and Marty.

Got some paperwork and final check of calibration to do on the Nissan Elgrand I just converted and then hopefully I'll be able to get onto it..

Cheers, I'll keep you posted.

Simon

Pics of the general leak position below, though I could only just about see the actual leak. It's about as far forward as the rear airspring and just in from the chassis, I removed the wheel arch liner to see if I could get a better view from that angle. While under the P38 I noticed all the brake pipes look shot, I didn't check when it passed the MOT but it must have been borderline then. The only thing I did to cause the leak was press the brake pedal fairly hard while holding just above idle rpm in drive while stationery (useful to do as early part of calibration), probably just as well the leak happened under those conditions than while customer's wife was driving it.

I knew I had a busy day with about 5 customers coming including the owner of the Elgrand I just converted coming to collect it, another Elgrand owner coming for a chat and 'East Coast Customs' owner bringing his Jeep back from Hull hat I swapped the front end on maybe 6 months ago. Off topic but the Jeep was fixed in 5 minutes, just as I predicted from what he'd told me on the phone the problem was just a bad system earth.

So I copped out of fixing the leak and decided to let my mate at Joe's Garage sort it lol. Joe's only half a mile away and East Coast Customs guy didn't mind following me through as I drove the P38 trying not to use the foot brake, brought me back and I fixed the Jeep. Joe didn't get to look at the P38 until 5pm, then called me to say 'I cant fix this mate, cant even get to where the leak was but I pulled on the pipe and the broken bit just came off so I crimped it up to slow the leak'. Joe came and picked me up and I drove the P38 back to mine. I've called Simons Services, a Landrover specialist in Normanton WYorks who I've done a lot of work for before.. He'll definitely be able to fix it but I'll leave that up to the owner. I've emailed the owner, don't have their phone number (maybe because I recently got a new phone when old one broke and last synchronised old phone numbers years ago), explained all this, I await their reply!

Pics. The screwdriver is there to mark the position of the leak.

Simon