Brakes need pumping

[swifty]

I have a 72 swinger with power brakes and BBP discs in front. If the car is sitting for a while the brakes need to be pumped once or twice and then will work fine. Most of the time driving brakes work fine. Every once in a while brakes will be weak, give them one pump and work fine. I thought it was air because I could not get one front bleeder open. After alot of Kroil and heat I finally got it open and bled. Very little to none air. The brakes are firmer but still occasionally need a pump. What do I look for: air in system, bad master cylinder, bad check valve for brake booster? Engine is stock worn out 360, still has 18" at idle, did not check when in gear. Just wondering where to go next?

 

[74Dusted]

I'd try bleeding them again, air can cause this.

But, this is almost always a sign of a master cylinder failing. I bet if you unbolt the master cylinder from the brake booster and slide it out a little to look at the booster, it's soaked with brake fluid inside. The engine is sucking up that fluid and burning it.

If this was a Manual (no booster) Brake car, your firewall and floor would have brake fluid from fluid leaking out of the master cylinder.

 

[1968FormulaS340]

I would start with bleeding the entire system. Bleed them until all of the old fluid is out and see where you are.

 

[godfatherofchry]

I would start with bleeding the entire system. Bleed them until all of the old fluid is out and see where you are.

X2.. and if you cant see the bottom of the reservoir its time to change the fluid any ways.............

 

[swifty]

I'd try bleeding them again, air can cause this.

But, this is almost always a sign of a master cylinder failing. I bet if you unbolt the master cylinder from the brake booster and slide it out a little to look at the booster, it's soaked with brake fluid inside. The engine is sucking up that fluid and burning it.

If this was a Manual (no booster) Brake car, your firewall and floor would have brake fluid from fluid leaking out of the master cylinder.

I have kept an eye on the vacuum line and it always looks dry. I will try bleeding the master cylinder and then the entire system again. If this does not work do we agree I need a new master cylinder?