Why have I lost my brakes?

[BZG Wagon]

I seem to have lost braking ability in my Nissan Terrano.

Symptoms:
1) When I pump the brake 2 - 3 times (car running) the pedal goes hard and the handbrake light comes on. It feels similar to stopping it when the engine isn't on.
2) If I slam hard on the brakes the pedal goes (almost) to the floor and the truck gradually comes to a halt. But massively diminished braking ability.

Can't see any obvious leaks, and the fluid is completely topped up. Driving normally the brakes seems relatively normal; just hard stops or repetitive use of the brake it fails.

Any ideas?

[Dell'Orto]

Sounds like a leaky master cylinder...unsure why the handbrake light would come on though, that's usuallly related to fluid level.

[matt dunn]

the truck gradually comes to a halt.Any ideas?

I presume by that that the vehicles is a diesil of some sort?

Will be either slipping fan belt, stuffed alternator vacuum pump,
or a vacuum leak somewhere.

The handbrake light coming on means that vacuum is low as most diesil's have a vacuum switch to monitor brake vacuum.

[Grrrrrrr!]

I'd go with failing brake booster.

Diesel or petrol? If petrol check for vacuum leaks etc, If diesel look at the alternator, the vacuum pump is on the back IIRC.

[BZG Wagon]

Yes it's diesel.

Will have a squiz tonight and see if anything obvious is loose or has come off.

[evil_si]

Like matt said loose alt belt or Its vacuum pump will be stuffed,

Diesels have a small pump on the back of alternator (usually) to generate vacuum for the brakes

Pull the big hose off the top that runs to the booster and see if its sucking

[THA SHZ]

also if its rear drum brakes make sure your axle seal hasnt gone and its been leaking oil into your rear brakes , had this happen with the hilux