79L824SPD

Have a issue with my brakes. It's a 79. Brake pedal feels fine when just slowing down, but when you come to a stop the pedal will be at the top, then slowly go down, sometimes to the floor. I'm thinking master cylinder? Am I correct with that or could it be the booster also? Thanks in Advance!!

Sayfoo

Probably the mc. I would bleed the brakes first. Sometimes a lot of air in the lines can confuse things. To check the mc, engine off, pump the pedal a few times to get a hard pedal, then keep the pressure on. If the pedal goes down over the next 20/30 seconds, then you were right.
I went through this about 2 yrs ago. 1st Napa rebuilt unit was bad out of the box. I returned it and got another brand. It failed while bench bleeding (leaked out the rear seal). Napa said that they had alot of returns lately and just gave me my money back.
I then bought a new AC Delco and it had a China sticker on it. It started to fail recently like yours, so I went retro and bought a new reproduction unit. No indication where it was built, but it is now working fine. So, the point is, you have to be aware that some parts are bad right out of the box. If you replace your mc and you still have a problem, it doesn't necessarily mean it's not the replacement part.

79L824SPD

Thanks for the info. I did what you said today and sure enough the pedal went down, although slowly. I'll try a master cylinder. I'm pretty sure its original to the car. Does anyone know anything about those so called easy bleeder screws I see in the catalogs.?

Sayfoo

Be sure to bench bleed it before installing. Instructions can be found on this forum.
Good luck