Braking Problem

[78blazaer]

I have been having some brake issue on my 78 Blazer (low brake pedal, hard to stop). I bleeded the brakes several times and got all of the air out. When I hit the brakes, I hear a gust of vaccum air comes out around the brake pedal/booster area when I pressed on the brake pedal. I think the problem maybe the brake booster. Does anybody know how to diagnose a vacuum operated brake booster? I am about to give up on this issue and thinking of upgrading to hydroboost instead.

Thanks in advance.

 

[chevydan3]

I had the same problem. It was the vacuum booster. Replacing the booster fixed the problem. I also replaced the master just to be safe, because it was leaking.

 

[78blazaer]

I'll try replacing the power brake booster. http://www.autozone.com/servlet/UiB...e|~REGULAR+PARTS+LOOK+UP|~BRAKE+POWER+BOOSTER

Thanks for the info.

 

[diesel4me]

its hard to tell

The "official" test of the booster is to pump the pedal several times with the engine off --then apply the brake,and start it up--if the booster is working,the pedal will sink toward the floor slighty--after you shut it off,you should be able to push the pedal 3 times before it gets hard again....the only problem is many times when the diaphram fails inside the booster,its not a huge leak,and might not leak quickly,or badly enough to affect the power assist every time you step on the brakes--and then when you need it most--NO power assist!!

I'd reccomend getting the master cylinder and the booster as a rebuilt unit together,since an old master cylinder can leak into the new booster and damage it--its not that much more for both...or if you are short on cash,you could search the junkyards for a good one--my 79 C10's booster croaked his summer--all the junkyards had no 79-80 trucks with good boosters(the only years that the Hollander interchange book said would fit,and had many questions,like single or dual diaphram,rear brake size,etc)--I ended up finding one I had lying in my shed from a 73 K10 that fit perfectly,and stops just fine!--I just hope it lasts a while,since it was sitting for years..didnt have the dough for a new one--guess the book isnt always gospel when it comes to interchanging things...