Landcruiser master cylinder diagnoses

[Jimmytno1]

Evening all, I know this should probably be in technical or Japanese but was after a bigger audience to confirm my diagnosis of a faulty master cylinder! Customer arrives yesterday morning with no brake pedal and no fluid in the reservoir, a quick inspection revealed two heavily corroded rear brake pipes,
one of which had rusted through hence the vehicle losing all it's fluid, vehicle is
a 1998 landcruiser collorado, 3.0 D with ABS by the way! Two brake pipes were quickly made and fitted and the brakes bled out but we just can't get a brake pedal, we can get fluid out of each corner of the vehicle and there is no air in the system but the pedal sinks to the floor everytime, we have tried several different bleed procedures, engine off, engine running with pedal depressed half way/fully with bleed nipples open etc, to no avail.
With all the hoses clamped off there is still no brake pedal so usually this would confirm to me the master cylinder is at fault but for some reason I'm only 99% sure! Does anyone know of a different bleed procedure than I've already tried? Sorry for the long post, I'm just not keen on charging a customer for a part when I'm not 100% convinced it's right!

Edited by Jimmytno1 on Tuesday 23 November 20:40

[Jimmytno1]

Not sure how the smiley thing got into the title, and balls! Spelt diagnosis wrong!

[davepoth]

There could be air in the master cylinder, which sometimes happens on some cars. Not sure if the land cruiser is afflicted though. It may need bleeding on the bench.

[Jimmytno1]

There is a bleed valve on the master cylinder which we have bled out but still no pedal!

[TheEnd]

Two man bleeding or pressure bleeder? Some systems need the ABS pump cycled if they have been ran dry.

It would only be a master cyl problem if the seals were knackered by a bit too much pumping without anything in there, and I'd expect it to have a leak if that was the case

[spaximus]

It is possible that the master cylinder seals are now torn.What happens is that the usual stroke of the master cylinder is say 1/3rd of the bore, when you bleed the brakes you use the full stroke. As brake fluid is hydroscopic (takes in water from the atmosphere)the bore may have some corrosion at the bottom which tears the seals. When you open a bleed nipple there is enough seal to push fluid out, but when you close it off the pedal can be pushed down as the torn seal allows the fluid to pass over it.
This was a common fault on old VW beetles.