Brake Problems...

Simmo · tinkerer Joined: 05 Oct 2001 Posts: 58

G'day fella's.

Ive just replaced my back drums, front calipers, and master cylinder with units i know are working perfectly. Brakes have been bled succefully several times. I now have brakes, but they are very strange, in that the first half of the brake pedal travel there is very little resistance and similiar amount of brakes applied. The second part however is firm and braking suddenly comes on very strong, making it very hard to pull up smoothly cause the brakes just grab all of a sudden.

It could be my booster, but the power assistance is still more than acceptable, even though there is evidence of vacuum leakage (ie engine revs change when fooot on brake).

My thought is that the proportioning valve under the master cylinder is rooted, this is supported by my only being able to lock up the back brakes on severe braking.

any thoughts?? i dont really want to spend $250 on a reco booster unless i have to. Sorry for the long post,

Cheers, Simmo.

RJM · tinkerer Joined: 10 Oct 2001 Posts: 109

Sounds like the brake booster is stuffed. Replace it.

If there is a vaccum leak first check the hoses etc, if ok then do the above.

Have recently had the same problem, got a another unit for $50 bucks. Now pulls up nicely.

Ben Wight · backyard mechanic Joined: 04 Oct 2001 Posts: 946

Sometimes when you play with the shaft of the booster, which you might have done when changing master cylinders, it moves a seal inside the booster which gives the symptoms you mentioned.

The easiest fix is the take the booster to a brake joint and they will unscrew it, fix/replace the rubber seal, and screw it back together. Only cost me about $15 6 or so years ago.

Ben Wight

Simmo · tinkerer Joined: 05 Oct 2001 Posts: 58

alright, cheers feela's ill give it ago.

Simmo.