Brake problem 300tdi

I went to my caravan today to start my p reg 300tdi for the first time since last September !
I took a fully charged battery with me as I had taken it off when I parked her up.
Fitted the battery & to my joy she started first turn of the key. Idled nicely no smoke & no funny noises ! Tried the clutch, fine, 4 Hi, 4 Lo & difflock all fine. I hadn"t left the handrake on (chocked a wheel) so that wasn"t siezed. Put her in reverse & the brakes were jammed on. Selected Lo reversed & the brakes freed off.
Pressed the brake pedal & it went to the floor ! Pumped it several times & it became firm but then after a few seconds (with my foot on it) went back down to the floor. Drove around the site for a while pumping the pedal with the same result, went firm after several pumps then I could press it to the floor. Pumping it I could stop (doing 10mph) but only just !
The brakes are way to bad to drive it off site to a garage to get them looked at (nearest is 20 miles away) so I need to sort them myself. Or at least get them working good enough to get to a garage.
Brake resevoir is full.
Could the cylinders/callipers be seized, brake lines leaking, master cylinder gone.
Any idea where I should start looking ?
Any advice greatly appreciated.
Thanks in advance.

headlight

Sounds a bit like one of the master cylinder seals may have turned, if you have no fluid loss, get someone to pump pedal while you look in top of brake fluid reservoir, you may see bubbles??
if not, clamp each brake hose in turn and press pedal this will eliminate calipers, if the pedal still drops i suspect replacement master cylinder
good luck#Billy

billyloadsamud said:

Sounds a bit like one of the master cylinder seals may have turned, if you have no fluid loss, get someone to pump pedal while you look in top of brake fluid reservoir, you may see bubbles??
if not, clamp each brake hose in turn and press pedal this will eliminate calipers, if the pedal still drops i suspect replacement master cylinder
good luck#Billy

Click to expand...

Right I went back to my caravan this afternoon & took a mate with me.
I started the Disco & got him to pump the brake pedal whilst i looked in the reservoir. Didn"t see any bubbles but every time he pressed the pedal a jet of fluid spurted out of the resovoir !
I take it this shouldn"t happen & the master cylinder is knackered ? I assume that the seals are knackered & allowing the pressure into the reservoir instead of down to the calipers.
Does that sound right ?

headlight

headlight said:

Right I went back to my caravan this afternoon & took a mate with me.
I started the Disco & got him to pump the brake pedal whilst i looked in the reservoir. Didn"t see any bubbles but every time he pressed the pedal a jet of fluid spurted out of the resovoir !
I take it this shouldn"t happen & the master cylinder is knackered ? I assume that the seals are knackered & allowing the pressure into the reservoir instead of down to the calipers.
Does that sound right ?

headlight

Click to expand...

Something like that, new master cylinder needed.
Try paddocks.