Touchy brakes?

[punisher72]

Hey guys. When i brake i just touch the peddle and the brakes are very deadly? If im not careful we all would fly through the window? The peddle dosent feel hard to push like normal,its very touchy. Could this be too much vacum? The brakes have done this since i got the challenger?

[dodj]

If it's the rear brakes, check for a leaking axle seal.

[punisher72]

Definately no leaky rear seals and the rear slave cylinders were replaced! It feels like the front?

[Bullitt-]

I just Googled "touchy brakes" & other than the standard "oil on the pads make brakes grab" reply I found a few references to leaking boosters
"Check to see if your brake booster can hold vacuum. I went through a lot of trouble to find mine was leaking and was causing a very soft and touchy brake pedal while the car was running. The pedal was very hard with the car off. If I ran the car, it would have 1 pedal of "assisted" brake pressure then it would be hard again. It should take 2-3 pedals to get hard after shutting the car off."
  http://www.starquestclub.com/forum/index.php?showtopic=100870
  Turns out that a leaky booster can create this symptom. 

[punisher72]

Thanx Bullitt! My pedal Is really hard with motor off,and I'm not sure if it takes a couple of pumps to use up the vacum? I thought I might have too much vacum???

[Bullitt-]

  Hard pedal with motor off is normal but you should have a pump or three, right after shutdown, before all the vacuum is lost. I think a vacuum gauge would be the best way to test for leakage.
   Another item to look at is the check valve, that is the plastic part that the hose connects to, if it is bad you can have issues although maybe not this one.

[UKcuda]

Is this front discs or drums. 

If you have power front drums and they are not set up right they can grab like crazy - I once had it on a '68 Chevy stepside and it was like you say - "we're all leaving now, right out the front screen"

[punisher72]

The front is disc and the rear is standard drum! Im not home to check the plastic valve right now! Maybe i could try pinching the vacum hose a little to restrict the vacum??

[punisher72]

I tried my brakes today after the motor was shut down and i got 3 or 4 pumps before vacum run out? I took vacum line off when motor running and it sucks like crazy!!!!!!!! The booster looks new as its just metal and un painted? Any help or other ideas to check whats wrong? Could it be the proprtioning valve not adjusted correctly?

[Supercuda]

This is likely a booster problem. Many rebuilders now make a more "generic" product than they used to, and it is easy to put the wrong parts into a booster, or to incorrectly box the completed remanufactured part. A new booster should correct your problem, but don't expect it to go away any other way. The last time I ran into this, it was on a Ford pickup truck. booster, I got the exact complaint you have, and it would not go away, no matter what I adjusted, or how it was adjusted. I told my customer this, and warned him not to use his brakes aggressively (he needed his truck NOW). If he wanted a solution, I could have a new booster after the weekend. He loved it! Go figure. Basically, your booster is over-assisting your brakes, and this cannot be solved without replacement.

[punisher72]

Thankyou Supercuda. I was affraid i would hear that Its just more money i guess 

[Supercuda]

Sorry about the bad news. There is a possibility that you could make this liveable, but it requires some work and a LOT of patience. Check the pushrod length, coming out of the front of the booster. If it is longer than it should be (check a repair manual for the full procedure), shorten it. If it is the correct length, you can also shorten it, but I can't recommend this as a fix for your problem. I suspect that it was correctly assembled, and you just have to get one that is built right for your car.

[punisher72]

I noticed yesty that when i brake,the pedal is getting close to the floor before it takes up so to speak!!!! When u pump it up  the pedal stays in the same position? Could this be about the rod your talking about Supercuda? They work fine so im sure they dont need bleeding

[Aussie Challenger]

This is likely a booster problem. Many rebuilders now make a more "generic" product than they used to, and it is easy to put the wrong parts into a booster, or to incorrectly box the completed remanufactured part. Basically, your booster is over-assisting your brakes, and this cannot be solved without replacement.

Some boosters are made for low vac. motors and they have the effect you describe or the reaction valve inside your booster is faulty.

[Supercuda]

You didn't mention a low pedal before. This might be salvageable after all! Check the booster pushrod length. If your brakes are low, and seem to apply only at the bottom, and with unusual force, the pushrod is likely TOO SHORT. I have seen more of this in recent years, as more people lose the skills and techniques necessary for his "oldschool" technology. The advent of "packaged" repair parts has helped this along, and the new crop of "technicians" out there often have no idea how to adjust anything. The procedue and specifications should be in ANY repair manual for this car, and it is simple. All it requires is the removal of the master cylinder from the booster, and you don't even have to open the hydraulics. Measure the depth of the m/c piston hole, and compare this to the booster pushrod protrusion. This dimension should match, or nearly do so. I am betting, from this last tidbit, that yours is too short by about 1/4".