Hear air when i push down the brake pedal

Spray brake pedal (treadel valve) With WD-40. May have to remove foot pedal and rubber boot work up and down with pliers until moves freely.

If brakes are mushy then you still have air in the lines.Did you bleed all 4 wheels?have wife push brake pedal down once and hold then bleed hold down one and bleed and so on if this has a quick takeup master cylinder pumping 3 or 4 times then bleed wont work

The air seeping is a dead giveaway. Your power brakes are now manual brakes, but stiffer. The diaphram in the brake booster has torn and the hissing noise is the engine vacuum escaping (you hear it louder when you depress the pedal right?). Replace the booster and you will be fine. The brake lights probably don't work because you can't push the pedal down far enought to release the switch. Please rate. Thanks.

Just keep bleeding the brakes the air will come out. If you have two people one on the brake pedal and one at the brakes have the person at the pedal push the pedal and hold it, the person at the brakes opens the line then closes it with the other person still pushing. once it is closed theperson relieves the pedal. do this 3 to 4 times then check the fluid level and fill. do this to every wheel starting with the wheel furthest from the master cylinder and working your way closer. Also some thing to check is if you have drums in back is the adjustment of the brakes. If they are not adjusted properly you will not get the full pedal. they should be adjusted out close to the drum but not rubbing. also beware of the lip on the drum. it will throw you off. if you can take a grinder and grind off this lip. The method i just explained pushes fluid thru faster. I have had to do this a couple of times on some vehicles.
Good luck
Randy

not sure if you mean while driving or when parked with the ignition off but here are a couple reasons on why the brake pedal may be high and low at different times. If the vehicle is running the brake pedal will feel the same just about every time. If the car is off and you step on the brakes it will get harder and harder to push down since there is no vacuum assist. Another reason would be the brake pad thickness. New brakes the pedal will feel higher where as worn brake pads the pedal may feel lower. Another reason would be if you have air in the brake lines. this will make the pedal feel mushy and soft at first and firm up as you pump the brakes. Hope this helps.

usually an indicator of either a loss of pressure due to low fluid and/or air in the system (brake fluid leak) or extremely worn rear brakes (if drum brakes in rear). possible causes include master cylinder (internal fluid pressure leak), external fluid leaks (calipers, lines, wheel cylinders), rear drum brakes extremely worn down or severely out of adjustment. normally worn disc brakes may reduce pedal height SOME, but seldom "to floor". but the "mushy" quote combined with the "floor" quote suggests a hydrolic fluid pressure problem.

If your power steering is whining you may just be low on power sterring fluid. I would check that first. If that is good your power steering pump may be on its way out.

There is a power brake booster in your system, but that should not affect if your brakes feel "mushy". I would look at the master cylinder, you probably need a new master cylinder they have a tendency to leak fluid past the seals as they age giving your pedal a mushy feeling. I woould also check your brake lines on each wheel to see if one might be leaking, this will give you a mushy feel as well. I doubt that is the case if you aren't loosing fluid however.

seems like you have air in the lines need to bleed the brakes

They need to be bleed again all four wheels but your vacuum pump may be bad since diesels don't have vacuum then have to have a pump, check that the booster one way check valve is good if you can blow thew it both ways it's bad, to bleed start from the wheel farthest away from the master cylinder pump the brakes 5 times and hold down then open the bleed valve keep doing this until you get clear fluid out of each wheel once you have done that if it is still mushy and you know you have vacuum re bleed with engine running this will help push more out with power assist. most like the hard brake pedal had to do with no vacuum check out the pump. You may also have to reset the 2 way check valve if you need help with this let me know.

Well this is very serious I hope you deal with it right away. You mentioned that sometimes the pedal was hard,do you mean that its all the way up and it doesnt feel like you have power brakes?? If so have you noticed any sounds like air escaping (swoosh sound when brakes applied)? Failure of the power booster causes pedal to become very hard and could possibly be your problem for hard pedal if I understood you correctly. check to make sure that vacuum to the booster is conected properly and hose not kinked..Now for the solution for the pedal fading to the floor... You either have air in your brake system, A bypassing master cylinder , or a hydraulic leak...Were your brakes serviced recently?? if so try bleeding your brake system first...That would be the first step if still the problem persist I would isolate exactly where the problem was coming from.. To do this you would start at the passenger rear wheel and line clamp the brake hose to make that part of your brake sytem inoperable...when clamped try your brakes and note if brakes improved or had know affect on system (when testing obviously im not suggesting you drive to determine results of test procedure)repeat test for each wheel you have isolated the problem when brakes feel normal with one wheel clamped,which ever it may be.. This isnt as hard as it might soun and if you are confused at all dont hesitate to ask questions... Remember the only dumb question is the one you fail to ask I would hate for you to get into an accident ... Good luck!!!