Guinea Jay

I did the master cylinder about a year ago. I don't see any leakage there or along the brake lines and calipers. I can build up pressure if I pump the pedal but if I go just a short time without doing it the pedal will almost hit the floor.
Doesn't seem like a tough job at all, I've gotta put her away for the winter and do a bunch of other stuff anyway, but I want to make sure before I spend $200 on a new booster.
Oh yeah car is an 85. Thanks

1st87

is the brake fluid level down?? if so then it could be rotted line or caliper. are you stepping on brake with car running?

Nowhere Man

if your fluid levels check out that sounds like a booster

samsonb

Are you having to pump the pedal to get brakes? If so, then it sounds like a bad master that is leaking internally. Also, it sounds like a bad master with the pedal almost hitting the floor.

Brake Master Cylinder Troubleshooting:

www.trustmymechanic.com/master_cylinder.htm

RollaMo-LT4

The symptoms described does not sound like a booster issue.
If the pedal goes to the floor, that is a brake fluid issue.
Air in the lines or a leak of some sort, even could be internal to the master so you wouldn't actually see a leak.

A bad booster would act like your car had no power brakes, with a very hard pedal.

86PACER

A bad booster won't cause the pedal to nearly botton out. A bad master will. A bad booster causes you to have to press the pedal extra hard to stop.

If when you come to a stop sign and the brake pedal slowly sinks further and further to keep the car still it's a bad master.

Muffin

The votes are in and counted:

Mastercylinder---80%

Booster---------- 5%

Other-------------15%

jesredvette

I had a bad booster last year. The pedal didn't go down any farther; it just felt like I had no power brakes and I had to push like hell to get the car to stop. This sounds like a master cyl issue. Might not be a bad idea to give the brakes a good bleeding before spending any significant dough. If bleeding doesn't resolve it, it's clearly the master. Avoid cheap aftermarket stuff; go with original ACDelco if you can.

oldalaskaman

check your rear brakes, bleed all your brakes in the right order, it wasnt done enough last time and you have air in the lines, and check your hand brake adjustment.

jpanek

My booster went bad after about a year, because 1 of the 2 attachment bolts loosened up and then I was pushing on it at an angle, which I suspect killed it. Make sure you put loctite on the fasteners, or you may have to do the job an extra time...don't we all just love going upside down under the dash?

samsonb

I don't think I'd want to put locktite on them. As those bolts are hard to get to and would make it a harder job if the bolts were stuck on from the loctite.

I made sure I tightened them up good when I installed my booster.

Guinea Jay

Thanks for all the help. I'm actually hoping it's the master cylinder since I just bought it last year I think Autozone will give me a free one. Haven't had time to get to work on it yet.

wjalex4

Oh, the brake light on the dash. It comes on when I pull up on the parking brake lever, and goes back off when I push the lever back down. I Have not seen the brake light come on during any of these bleeding procedures or my subsequent testing with my foot on the break pedal.

drcook

You are in a 9 year old thread. If you are having an issue, create your own so that the solution/suggestions are for you, not getting mingled in with folks not seeing the other posts are 9 years old.