Hello,
My 1990 245 has an issue with the brakes. The pedal will sink a bit if not used for a bit while driving. I hear a creaking when stepping on the pedal as well. The Master Cylinder is full and I don't have any leaks.
I have to give the pedal a quick double ump to bring it back up, not all the time but aftet driving for a while w/o using the brakes. Like on the highway !
Thanks for you help as usual.
Philvo

If it's just a matter that you have to step down farther after a long drive, but that it doesn't continue to sink (i.e., at the low point it's still solid, just lower down), then it isn't your master cylinder (or brake booster).

The problem is that there is some irregularity with the rotors (one or more) -- driving for a while tends to slowly but gradually push the pads away from the rotor's surface (as if you were compressing the caliper's piston), so with that first jab of the brake pedal you have to press farther in order to push the piston out farther.

Thats probably it as I replaced one rotor when I did the driver's side wheel bearing. Looks like I'll do the passenger's side tomorrow even though that bearing is fine and the rotor looks good. The driver's one was scored....
Thanks, Phil

re: "...I replaced one rotor when I did the driver's side wheel bearing..."

A bad or incorrectly tightened wheel bearing will also cause this -- anything that will cause the rotor to wobble -- because it will push the pads away from the rotor surface as it spins. Are you sure the hub was tightened (and the bearings seated) properly? Or the "hat" of the rotor seated on the hub straight, without anything (piece of debris) beneath to make it cocked to one side?

Hi Ken,
You nailed it. My hub was a little loose, I got another two turns(by hand of course) on the castle nut. I also installed two new rotors and pads and my brakes work great. Nice, high hard pedal and no pulsating whatsoever. I am glad I investigated as I commute to 30 miles to work and it wasn't safe having to pump the brakes.
Thanks again, Philvo

That condition sounds to me like you may need new brake pads.
It's also possible that you have air in the braking system.

I don't believe it's the booster causing the problem.

With the engine idling, pump the brakes up and hold pressure on the brake pedal.
Does the brake pedal gradually travel down to the floorboard?
If it does, that's a indicator of a faulty master cylinder.

If the brake pedal remains firm and doesn't sink to the floor board, that's a indication that the master cylinder is OK.

Is the brake fluid resevoir full?
Have you added any fluid lately?
When were the brake pads last changed?

steve

In checking the MC, use a gentle steady pressure, as when stopped at the lights, and see in pedal slowly sinks.

Excessive pressure pushes the seals firmly against the MC walls and stops leakage past bad seals.
--
1980 245 Canadian B21A with SU carb but electronic ignition and M46 trans in Brampton, Ont.

double pump not ump...

If the pedal is sinking with steady pressure on the pedal the MS is leaking internally due to failing seals.
If so replace it.
Dan