BRAKE ISSUE

[tvr2152]

Hello,

Hoping someone can help with a brake problem on a Jeep Cherokee Limited CRD A 2007
The issue is while driving if you pump the brakes you have a hard pedal but the brakes feel like there is no servo.
Can't find any leaks and my mechanic is stumped.

[stevieturbo]

And is there a reason why you're pumping the brakes while driving too ?

[tvr2152]

Yes, I had issues with a universal joint on the rear prop shaft.

[InitialDave]

If you come out to the car after it's been sat for a while, put your foot hard on the brake, and then start the engine, does the pedal feel change as it fires up?

[GreenV8S]

If it's a petrol engine the vacuum is supplied from the inlet manifold depression when the throttle is closed. Since the throttle is normally closed when you're braking, that works fine. If you're left foot braking while the throttle is still open there will be less / no vacuum available. A brake servo will have a non-return valve which would normally hold vacuum for you but even a slight leak would deplete this over a few minutes, and if you've been pumping the brakes it would be depleted almost immediately.

Perhaps yours isn't a petrol engine - otherwise I can't imagine why your mechanic didn't explain this to you.

[Smint]

If you pump the brakes repeatedly its possible you are using the servo assistance faster than it can be replenished, whether this is a fault or not i don't know.