Got two 1978 thunderbirds and my little blue bird has only the front brakes working.I was told that its the proportioning brake valve,and that I needed another P-valve of the same yr.,and make. is this true or are there options besides finding another 78 t-bird and chance taking one off another 78 bird,hoping it works.
“I was told” Told by WHO?? Chances are, it’s the master cylinder…You have a double chamber master cylinder. The chamber that feeds the rear brakes has probably failed…Much more likely than the proportioning valve…A good brake shop will have pressure gauges that can be installed on the master to check available pressure…Or you can just by a new one…
Loosen the line (at the master cylinder) that feeds the front brakes. Get in the car and push the brake pedal down. If it goes all the way to the floor, the master is shot…
There are 2 inlet ports on the proportioning valve. How many outlets are on it? If there are only 2 outlets, one to the front and one to the rear, how can the valve cause one front caliper to operate and not the other? Take a close look at your valve and post the inputs and outputs.
"how can the valve cause one front caliper to operate and not the other? " Where did you see that Knox??
Thanks for the reply,the answer is Yes I put a new master cylinder on it,and still get only front brakes.And I took car to midas and they did same as you suggusted,with the finding I mentioned.(proportioning valve is shot)So I’m back with my original questain, Do I have to find a same yr.,make and model propotioning vave? or are there options??
I suggest you find a real mechanic and quit trying to cheap it out. This is obviously beyond your abilities. This might cost you some bucks, but the car will work properly.
Oh, and it’s obvious Midas doesn’t have real mechanics either.