pedal is soft at the bottom
my car is 1970 2 door hard top swinger power steering and non power brakes with the complete suspension ( front disc and rear drum) and drive train out of a factory V-8 1974 swinger 2 door hard top and i don't remember now if the 74 had power brakes or not.
my car has the factory steel BBP wheels and 14 inch tire size from the 74 car. I never did anything to the brake lines nor the proportioning valve on the car so they are still 1970 stock form. I have new brake pads/calipers/rotor and wheel bearings in the front.
i know i am prob missing some important info you would need to help me. But my problem is The brakes seem to work OK at best and are super soft at the bottom.
thanks in advance Don
Do not continue to drive it this way!Do not continue to drive it this way!
Which M/C is in it? And what is it's history.And do you know the bore size?
What size and type of brakes were on the 70?
Were the calipers, or wheel cylinders ,opened?
Are the wheel cylinders and calipers operating correctly?With no seized parts?
Are the hoses new?
Can you assure us that the rear brakeshoes were correctly installed and adjusted?
As well the front pads, correctly installed, on true rotors, and freely floating on the pins? Is the M/C correctly plumbed to the P-valve?
Keep in mind this issue could be either; hydraulic, or mechanical, or installer, as well as a mismatch of parts. A soft pedal is the hardest problem to diagnose. But quite possibly the easiest to remedy. So there will be many question.By answering these and other question to come, it makes it easier for us,to, long-distance, come to a possible conclusion.
It's like having a tummy ache; Is it kidneys? or bladder,or stomach,etc, or just gas?
But here is a shortcut.
The absolute quickest way to figure out where the problem lies, is to clamp the rear hose off.In this way, the #1 most likely cause has been defeated; a problem in the rear.This is a highly questionable procedure, as it is easily possible, with old hoses, to damage them internally.This may not show up until weeks go by. Or almost immediatly. Through experience, I have never damaged a new hose with this method.
If the problem then goes away, then it is in the rear.
But if the problem persists, then you for sure have an issue in the front. It could still be hydraulic, or mechanical.Air in the system is always the first go-to. A quick check of the operation of the Compensating port, can reveal a lot.A large hit-the-hood gusher, on brake pedal release,instantly means there is air in the system, or a springyness in one or more components. A small fountain is normal, with the rear system clamped.No fountain at all points to an incorrect pushrod setting.Protect your painted surfaces.
-Assuming the C-port is correctly indicating,then the next place to look is at the rotors. New pads on used,unmachined rotors, would be next. This rarely works well. During the brake in period, the pad edges sit on the outer circumference of the rotors, where the rust and slag accumulate. This causes the pads to twist during a brake application,with the outer edge getting destroyed by the rust, and the inner edge just contacting on a thin edge. The result of this is very little brake action going on,a lot of leg power required to achieve any action,a long pedal stroke, and a spongy-bouncy feel to it.Additionally, once the pad has been ground down to conform to the outer ridge, it may still not sit flat against the rotor.And additional ridges there will continue to lengthen the break-in period, as the pad slowly conforms to the crumby surface.During this period the brakes will not have full performance, requiring a lot of pedal pressure.
-There are still two more possibilities in the front. If your rotor surfaces are fresh and clean; next we move to the caliper-piston to pad interface. If the pads are not sitting absolutely flat on the pistons, either due to bent pins, bent pads, or incorrect install, then they will act like little springs forcing too much fluid back to the master.Again the result is long pedal travel and a springy pedal.
-And finally are the hoses. When they get old, they can soft-fail. That is they can get soft and become like balloons, expanding with every pedal application, and retracting with pedal release. Guess what the symptoms are.That's right ;long pedal travel and a springy,spongy feel.
So if you are willing to clamp the rear hose,This pretty much takes care of the front.