master cylinder questions

[oldbeater p/u]

How can I tell if its out. My peddle goes to the floor. I changed a caliper and this was my end result. I did try and bleed it the moment i put new caliper on. I need to know how to test it or should i replace it?

[NISTECH]

if before replacing the caliper you did not have a problem you most likely still have air in the system. calipers can be difficult to bleed. fill your master up with fluid and have someone inside to pump the pedal.Rig up a bungy cord so that it will pul the pedal back up if it is pushed down. ( i usually hook it around the pedal arm just above the foot pad and the other end hooked to the steering wheel) open the bleeder screw. once open have your friend pump the pedal as fast as he/she can while the screw is open after a few blasts of fluid close the bleeder while they are on the down stroke. check your fluid level top as nessesary. Continue to bleed in the normal fashion, he/she pushes the pedal down you crack the bleeder to allow fluid to escape then cinch up and they release and push down again till all air is escaped.

In the future when replaceing a caliper before removing anything use a pair of needle nose vise grips or pinch off pliers to pinch the brake hose just before the caliper this will prevent any loss of fluid from the brake lines. also before installing the new caliper remove the plastic plug in the brake line hole and crack the bleeder screw place it so the 2 are somewhat level and at the highest point from the ground(gravity effect) pour fluid into the brake line hole till fluid backs up and comes out BOTH holes. this can be tedious but it will save you the headache of a difficult bleed such as your having. once it is full tighten the bleeder screw and keep the caliper so the line port is up. go to the car and screw the caliper onto the brake line snug as best you can you will tighten it complety once installed. install the caliper to the knuckle,secure your brake line and open your bleeder screw. now release your vise grips or pinch off pliers. allow some fluid to bleed off then close the bleeder. you should now be able to climb in the car and after a couple pumps(to press the pads against the rotor) you should have a near perfect pedal. if not a couple of bleed shots with your helper will bring it right up. the whole process from jacking the car to putting it back on the ground should take no more then 20 to 30 mins.(with the right tools)

[oldbeater p/u]

We did as you suggested and there is still no brake pressure. We can hear the master cylinder moving air with bleeder valve closed. Is that a possible sign that the master cylinder needs to be replaced? Any other suggestions to bleed the system?

[oldbeater p/u]

thanks for the info. But sad to say I still am having troubles bleeding out air.

[NISTECH]

fill your master up and crack the lines at the master and allow it to gravity bleed then perform your bleed procedure with those lines as you would with the brake bleeder on the caliper. no fast pumping on this procedure, just regular bleeding. after doing this if it is just air in your system you should get some pedal even a minimal amount. you may also need to bleed all your brakes since you may have trapped air elsewhere in the system.

Did your master run dry of fluid when you were replacing the caliper?

[p00t]

if you had the brake disconnected from the car and lots of fluid came out then air is in the lines. often the air will work its way higher up into other pipes.

just try bleeding out the wheel on the other side of the car, for example if its the right rear caliper you changed bleed the left rear as well.

also make sure you followed nistechs advise properly, when you bleed you must: push pedal down, open bleeder, close bleeder, pull pedal up and repeat. it takes awhile, its a *****, be patient.

good luck.