Ford Mustang Forum banner

1 - 7 of 7 Posts

·
Registered
Joined
·
25 Posts
Discussion Starter · #1 ·
I'm changing my front calipers on my 1968 Mustang. Do I have to bleed the back wheel cylinders as well. I have a dual bowl master cylinder. I don't think any air would get into the rear brakes but I'm no mechanic so I'm must looking for some advice.

thanks
 

·
Registered
Joined
·
503 Posts
Yupp you should be fine not bleeding the back. The only reason you would have to bleed them is if you're changing the wheel cylinders or rear brake lines. Since you aren't, the rear brake lines and cylinders are all still full of fluid with no air.

make sure you bleed the new front ones good tho :bigthumbsup
 

·
Registered
Joined
·
1,491 Posts
That is why everyone should switch to a dual bowl master. If you lose pressure or fluid in one, the other will still allow you to stop because it is independent.

Good Luck and BE Safe
Ron
 

·
Registered
Joined
·
38 Posts
first we need to address some common inaccuracies. a low brake pedal cannot be caused by a bad proportioning valve, a bad booster, the short and long shoes in the wrong position or a loose seal on the reservoir seal. pretty much the only things that will cause a low or no brake pedal is an external leak at a wheel cylinder, flex hose, steel line, a leak at the master cylinder rear seal an internal leak in the master cylinder or severely out of adjustment brake shoes. the hydraulic brake system is a completely sealed system that as you already know, can have no air in the system at all. any place that is drawing in air would also be leaking fluid. brake fluid is a liquid, and liquids cannot be compressed which is why it works. although the fluid flows through several components, it is basically a solid link to the brake shoes/pads. the proportioning valve simply sends a certain amount of fluid to the left and right front brakes and to both rear brakes. later model cars have a line for each of the 4 wheels, of course we're talking about pre ABS cars. even if the proportioning valve did have and internal leak/bypass, it would simply apply more or less fluid to either front or rear brakes. it's other purpose is to provide some kind of brakes in the case of a massive leak in the system rather than losing all brakes together. the reservoir cap seal could leak fluid around the cap, but as long as there is fluid in both chambers of the M/C, it will not draw air into the system. the brake booster simply assist in the pedal effort, there is no fluid in it and it is a solid link from the pedal to the M/C it will not cause a low or no pedal but will cause a hard pedal. a internally collapsed flex hose, front or rear will also cause a hard pedal but will not cause no pedal. Short or long shoes in the wrong position will not cause a no pedal situation. If fact, most brake shoe manufacturers do not even provide short and long shoes anymore. if you do happen to have short and long shoes, the short shoe goes toward the front.

back to your original problem. since you said that you had a sudden no pedal situation we can assume that the brakes are close to correct adjustment. if you don't have a mechanical failure such as a broken spring, which you would know because it would be noisy and you would have fluid pouring out of the drum/s and you don't see any external leaks, my first guess is that you had/have a bad master cylinder. assuming that you properly bench bled the M/C and properly bled the M/C at the lines when you installed it, you either have another bad cylinder, or still have air in the system. when bleeding the brakes, you should not pump the pedal more than 3 times and hold it down until you close the bleeder. the pedal should be pumped slowly. when the pedal is pumped rapidly or hard, it will airiate the fluid and cause no pedal. in this case, you need to let the car sit for a fairly long time in order for the bubbles to dissipate, you cannot bleed out these tiny bubbles manually. i;m willing to bet that you still have air in the system and patience is going to be the only way to correct the problem.
 

·
Registered
Joined
·
324 Posts
Mike, I think you posted your answer on the wrong thread. Wow what an answer for a simple question.:kooky:48445 just asked did he have to bleed rear wheel cylinders when he replaces front calipers. The answer is a simple no. Just bleed the front. Mike, you need copy your answer over to the correct thread he needs your answer hes not getting very good info over there. And I dont want to type that much like you did.:nogrinner lol. Great answer by the way. Heres the right thread I believe.http://www.allfordmustangs.com/forums/classic-tech/304577-stressful-braking-repair-problems.html
 

·
Registered
Joined
·
38 Posts
Mike, I think you posted your answer on the wrong thread. Wow what an answer for a simple question.:kooky:48445 just asked did he have to bleed rear wheel cylinders when he replaces front calipers. The answer is a simple no. Just bleed the front. Mike, you need copy your answer over to the correct thread he needs your answer hes not getting very good info over there. And I dont want to type that much like you did.:nogrinner lol. Great answer by the way. Heres the right thread I believe.http://www.allfordmustangs.com/forums/classic-tech/304577-stressful-braking-repair-problems.html
Oops, sorry!

Mike
 
1 - 7 of 7 Posts
Top