Please diagnoise this probelm....

I bleed the brakes and my buddy stated that we didn't have to bleed the master cylinder. Is that right? I have power brakes, disk up front and drums in the rear. For some reason, the brakes have to be pressed harder than hard for the car to come to a rolling stop. I got my muffler changed and the individual there said you may want to look at the vacuum lines, "They may not be getting info vacuum for the booster to work correctly". I have never heard of that. So I took pictures of the lines of how the vacuum lines are setup on the booster.

Here is the booster with two lines coming from it! (I know about the bent bolt, so no one needs to point that out ha,ha,ha)

View attachment 395492

The bottom line goes into this

View attachment 395494

The second line seems to go into the manifold (i think its the manifold) and gets split again.

View attachment 395496


The lines gets split and goes across the width of the car and goes into the other side of the fender inner side and connects.


View attachment 395498


If anyone can figure this out or tell me how to correct this it would be greatful.

2nd Mustang said:

You'll need a vacuum gauge to check the amount of vacuum your engine is pulling at idle. If it's too low (mine pulls 12 inches and is able to operate the brake power booster), then your brake booster won't work properly. Looks like one of the vacuum lines from the booster goes to the automatic tranny which may be leaking vacuum, but I would guess that it wouldn't shift properly if there was a vacuum leak anywhere. Maybe the booster just went south, which in some cases causes a very poor idle if the diaphragm is leaking inside the booster which would in turn cause a low vacuum reading also. Good luck.

Click to expand...

Thanks for your diagnoise! Yeah my idle is fine so if the vacumis less than 12 inches, can I safely say its the booster? Thanks

2nd Mustang said:

If your vacuum is less than 12 inches, I would say that either you have a vacuum leak or one wild cam! I have a mild hydraulic Crane Cam which is why my vacuum is only at 12 inches at idle. My booster went out a few years ago, but that caused a really bad vacuum leak. The engine wouldn't idle at all and the brake pedal was hard as a rock.

I would get a vacuum gauge first, before buying anything else. It is a very valuable tool for diagnosing many possible engine problems.

Click to expand...

2nd mustang,

So you are confirming that the lines are correct? And just to verify, if the vacuum is less than 12 inches it 90% can be the booster? The only reason why I say that is due to your previous experience "The engine wouldn't idle at all and the brake pedal was hard as a rock". I am experiencing that. Actually, here is my experience. Going 30 mph I have to begin braking about 20-30 feet ahead braking slowy. If I was going 30mph with a 10 feet gap and the person comes to a screetching stop I'd hit them for sure! Can anyone relate to this or diagnoise if that's the booster? Or can it be not bleeding correctly. My buddy said we didn't have to bleed the MC since we bleed all the wheels throughly!

geostang351 said:

Correct. Air in the lines would allow for the brakes to move further and mushy. I just redid my brakes this winter and had a big problem with a hard pedal and no stopping. Come to find that my 30 year Ganada original caliper was frozen on the passenger side. Are your calipers new or old? Just trying to point something else out.

I changed to new rebuilt calipers and have yet to try it on unsalted, cold New England Roads (I was so good to go until this last storm!!!!!! )

Click to expand...

I just bought the car 2 months ago and getting familiar with muscle cars since I was into imports. How can you verify if the calipers are frozen? If any of the calipers were frozen wouldn't that not allow you to brake or atleast on the wheel? Meaning you can feel car weave ? Just my assesment... Thanks for the tip on what to look for.