power brake booster

[pizza3260]

i have a 73 power brake booster that loses pressure,when i start the car i idle for about 5 mins. then pump the pedal untill i feel a good pedal.if i take off without pumping the pedal the pedal will go right to the floor.what's going on.

tom b.

 

[JonM]

Sounds like a master cylinder is shot...does the MC have fluid in it? I wouldn't drive it, if I were you.

 

[Steve Grodin]

I agree, definitely the master cylinder is bad. They can be full of fluid and still be bad.

 

[pizza3260]

the master cylinder is new & holds fluid.

tom b.

 

[Steve Grodin]

the master cylinder is new & holds fluid.

tom b.

I've had new master cylinders turn out to be defective right out of the box.

 

[cntrhub]

Try this. Don't start the car. Just pedel the brake a number of times to get all the air out of the booster. Now you should have a very hard brake pedal. It should not feel like mush, or go to the floor. It should be very hard and resists so, that it wants to come back up. If you don't have a hard feeling pedal, then you still have air trapped in the line from the M/C installation.
Did you bench bleed the M/Cylinder before you installed it? Did you begin at the farthest brake caliper for your first brake bleed? The sequence goes: R/Rear, then L/Rear, followed by R/Front, and ending with L/Front Caliper. Recheck your work before you buy a part that is not needed.

 

[Copdogcorvettes]

Well one last thing to check into; if everything is good master cly. power booster and all the lines have been bleed properly. Check the flex lines to each wheel. If they get old and if the car sat for a long time this could be the problem. My 78 had been in storage for a few years and i could not get a good pedal. I replaced the booster, the master cly and bleed everything three times. NO luck. I finally trailered it to the shop and said, "Fix It." All new flex lines and the problem fixed. This may not be your problem, but if all else fails you may want to check into that.

GOOD LUCK,

Gary

 

[pizza3260]

power booster

thanks to all i will start over from step #1,bleed the m/c & so on.

i have new m/c,flex lines & calipers.

tom