Outer Limits 4x4 Board

If you pump a brake pedal without the ignition off, it gets hard to push and the brakes are very hard to operate.
That's happening to my vehicle while I'm driving it with the ignition still on.
I've parked it in my driveway and don't think it will be going anywhere until I know what's going on, and then to drive very carefully to a brake specialist, but before I get told a whole heap of lies there, it would be nice to have SOME idea of what it could possibly be.
Any ideas, it normally clears instantly, and mostly seems to happen when steering hard to either left or right such as turning into a parking spot.

Thanks in advance for any ideas so I'll know what I'm hearing when the brake specialist gives me his opinions.

vacuum leak on the booster. check hoses otherwise vacuum canister, pump or booster.

i assume of course when you say ignition still on you do have the motor running.

With the engine OFF pump the brake pedal a few times and then hold it down,(this should use the vacuum in the booster) and then start the engine, if the pedal sinks a little upon startup your booster is working.
You don't say if it's petrol or diesel
If its a diesel then your vacuum pump may be faulty.

you say its when you do hard turns, could you be pinching a brake line somewhere? something quick and easy to check?

I had an issue on a high country tip just after Christmas.
Brake pedal would go hard and virtually no brakes.

Turned out that there is a one way valve that stops you loosing pressure in the system. This was positioned below the 2nd battery. The battery had been leaking and ate through the plastic and was loosing vacuum.

'89, 4.2 Diesel Patrol.
Thanks for the ideas of what it could be, might even save me a trip to a brake specialist if it's one of the things you've suggested.

Much appreciate the help.

Ezookiel wrote:'89, 4.2 Diesel Patrol.
Thanks for the ideas of what it could be, might even save me a trip to a brake specialist if it's one of the things you've suggested.

Much appreciate the help.

Add a good look at the vacuum pump on the back of the alternator (not there on petrol models)