MG MGB and MGB GT Tech Talk
Usually my brake pedal feels okay but after i drive my 1980 B for a while the brake pedal becomes hard and it is tougher to brake....car has a new master cylinder and brake lines and wheel cylinders are fine...any suggestions. Thanks!
This may be way off, but have you tried bleeding them again? Maybe when they stiffen up they're actually the way they're supposed to be.
If you didn't say new lines I would also say maybe your rubber hoses have deteriorated and the rubber flakes are cloggin up the pistons, happened to me once.
take a look to see if your brake booster is operating properly...is the vacuum line hooked up from underneath it to the Zenith intake? is brake fluid leaking back into it?
First of all make sure you aren't developing a vacuum leak to the brake booster after the car runs a while. Carefully check the lines, connections, and check valve. If you don't find the problem there it's inside the booster, Tony or Chris should have a good one on hand.
If it occurs ONLY after driving for a while there may not be enough free play in the pedal, or the rear brakes are over adjusted, and in either case the brakes are dragging and the excess heat generated causes the brake fluid to expand in the system and make the pedal become almost rock solid.
