Have a '94 D1 with about 101K. About 2 years ago the brakes suddenly failed while driving. The truck has been sitting since then and I decided to put it back on the road if I can and use it as my new Beach Access Vehicle for surfcasting. My current truck is an Expedition which uses too much fuel and is just too plain big... (get 14 MPG downhill with a tailwind!)

When the breaks failed ithappened suddenly while my wife was driving the truck.... really failed... I mean no break power at any wheel. The break pedal will make a whoosh sound of wind, but no real resistance to speak of, and travel to the floor. It does return on it’s own. There is no break fluid leaking anywhere I can see. Not the master, not the calipers, not the ABS unit, not from the servo, not a drop. In fact when you pump the break pedal, the fluid in the master cylinder clearly moves and sloshes.

I just can not figure out what caused this.Thought the most likely candidate was the master cylinder, and figured I would go ahead and try to replace that first.Maybe before I do thathave someone pump the break pedal and then back off onthe break lines at the ABS unitjust to see if there is fluid flowing there.

So.... Sort of half hoping a bunch a people on this forum would say HA HA... that is a commonfailure of a specific part in D1 Disco's... replace the XYZ what-cha-ma-call-it. Any ideas before I start purchasing parts?

Many thanks in advance!

SurfRat

 

Well the ABS modulator going out is a common problem on DI's. Pull the ABS fuse under the hood and no more problem.
But thats not your problem.
If the brake pedal goes all the way to the floor when you press it then you have no brake pressure, either from a bad master cylinder, a vacum leak or low brake fluid level.
You said your brake fluid level was fine so it is either a vacum leak or a bad master cylinder. I am betting on the master cylinder though.

 

Sounds like a master cylinder to me...

If it was a vacuum leak, you would hear it and feel the idle fall...