Brake Hydraulic failure

[garyd]

My son has just had a weird brake hydraulic failure on his van which we can't get to the bottom of. It is a 1990 2wd van with the 1.9 DG engine.

On parking (on a slope) he applied the brakes hard to ensure the handbrake was holding properly, only to have the pedal hit the floor. Investigation revealed significant fluid running from above the fuel tank that was definitely brake fluid. Since there is just a single brake pipe running over the tank (to the rear brakes) he got a replacement pipe and installed that. Testing the brakes produced the same escaping fluid. I'm not sure if the clutch pipe is also over the tank but that still seems to work and why should it be pressurised by the brake pedal?

He is 100 miles from me but our phone discussions have not lead to a scenario where brake fluid can be over the tank from any other source. Does anyone have any ideas where else to look, please?

 

[R0B]

I would be taking the dash binnacle off and having a look at the master cylinder.

[garyd]

Thanks Rob,
but what would you be expecting (or fearing) to find there?

[R0B]

It's got to be worth checking just in case. If it's leaking the fluid will run towards the tank.

[garyd]

The fluid above the tank is appearing under pressure - ie as a squirt. So it's not running from somewhere else.
 

[multisi]

Was the pipe that replaced the old one a 2 part or a long single pipe that went from the chassis mounted brake bias valve all the way to the rear.

[R0B]

The fluid above the tank is appearing under pressure - ie as a squirt. So it's not running from somewhere else.
 

You never mentioned that in your first post. I would not have suggested the master cylinder if you mentioned the squirt.

[garyd]

Multisis,
it was, and the new one is, a two part (Brickwerks) pipe and no, it's not leaking from the middle union.

[bigherb]

The front brake pipes also run above the tank.

[garyd]

Thanks for the photo. This is obviously a much earlier, air cooled, van but, if the brake pipe layout is still very similar in the late models, then it does suggest one possible failure mode.
The front brake pipe is shown crossing the vehicle by the forward spring perch brace. If the later ones run behind the brace then a split there could potentially project fluid backwards into the channel in the top of the fuel tank.
That's the next place to check out.

[multisi]

Later pipes run the same, only the brake bias valve unit on the chassis has been up graded.