Brake pedal goes to floor on first pump

[Yankee]

I have replaced the front calipers and pads, the rear wheel cylinders, and the master cyclinder. The brake lines were replaced with stainless braided lines prior to my ownership. The booster is still original.
What is happening is on the first push of the brake pedal it goes right to the floor. You can then pump it up and it will hold. It will not fall. There is no leak from anyway. I just re-bleed all the lines today and had no air in the lines. It also kind of sounds like a hiss noise when I push the brake pedal. My question is, is there some other ways to try and diagnose or repair this first pump pedal falling?

 

[klip]

Double check your rear shoe adjustment.

 

[Lead Head]

Did you bleed the load sensing proportioning valve? It has a bleeder and can trap air?

When I did the brakes on mine, I bled them RR, LR, LSPV, FL, FR.

 

[Yankee]

I haven't checked my rear shoe adjustment yet, and I didn't bleed the LSPV. I'll check those out tomorrow. Thanks for the suggestions.

Is it possible that my issue might be a bad booster as well? I'm unsure since it's 40 years old.....

 

[onemanarmy]

Of course the booster can go bad....but bleed the entire system again including the LSPV. Cheap stuff first

 

[BurntToast]

Keep bleeding till you loose your mind or the pedal gets firm. The booster won’t change it, just adds vacuum assist when the vehicle is running

 

[Godwin]

Did you check and/or adjust the booster push rod distance when you installed the new MC?

 

[too tall]

Adjust the rear brakes. The fluid flow is to the rear before the front. When the rears are out of adjustment you will have more pedal application to actually apply the brakes.

 

[franklin40]

pump up the brakes so they hold with the truck off. then start it while still holding the brakes. you should feel the power brakes make holding the brakes easier. (bad booster will make brakes firmer not pedal to floor). that’ll tell you if you booster is working. if you can pump and hold with no brake pedal fade your master is probably good (they can act up intermittently). my bet is you still have air in the lines (and or) brake shoes need adjusting. i had that exact thing happen and it was lsvp that i hadn’t bled.

 

[mongoose2231]

Also, check and see that the rear cylinders are installed correctly, with bleeder on top. They are interchangeable.

 

[Yankee]

Thank you for the suggestions everyone. I checked everything out today and was going to bleed it all over it again, and then realized that I hadn't mentioned that my landcruiser is a 1985 FJ60; therefore, no LSPV exists.

I'll go ahead and take the rear wheels off and check the brake shoe adjustment this weekend.

 

[Yankee]

Also, does FJ60s have self-adjusting brake shoes?

 

[mongoose2231]

When u use the emergency brake, they self adjust.

 

[Yankee]

When u use the emergency brake, they self adjust.

Interesting. I'll still check the brake shoes to see if something is funky. The bleeder is on top with the brake lines below it for the rears. When I bled the brakes last Saturday there wasn't any air in the lines that I could see, and there isn't any brake fade. It's just that the first pump of the brake pedal after driving it drops really far then grabs high when I re-press it.

 

[3_puppies]

are the rear shoes adjusted properly?

 

[duncanrm]

Loose front wheel bearings can cause this.. the rotor pushes the caliper back in as it moves. Jack up the front of the car and check for play in wheel bearings. If the vehicle was fine before the new calipers etc, and you haven't had the hub apart its unlikely to be this though.

 

[franklin40]

they may not self adjust if the bell cranks are seized. they are often rusted and don’t work. if your ebrake holds well then they’re probably ok though. on the automatics the ebrake rarely gets used so they seize up. on a manual they normally don’t. mine are not working properly though even though my truck is a manual. that’s on my to do list soon.