I've got a few issues with my brakes, and would love some further help. I'm pretty confused at this point. Originally, I was having an issue where I would brake, but require a bit of pumping to slow down at higher speeds. I replaced the booster with a new one from Zcardepot, and bled the brakes and master cylinder. When I bleed the brakes, the pedal goes all the way to the floor, but once the system is closed up, I have extremely minimal pedal travel, with not much braking pressure (I assume because the booster pushrod isn't pushing all the way through the master cylinder).

That said, I've adjusted my pushrod length, thinking that it was perhaps too long, causing the system to be preloaded. This caused the pedal to have a longer travel (barely), but had a significant dead zone before starting to slow down like it usually does (not much stopping force).

I have Wilwood Forged Superlight front calipers with 2-piece rotors, Wilwood 4 piston rear calipers with functioning parking brake, Tilton adjustable brake proportioning valve. I'm using a wilwood tandem master cylinder. Not that it makes much of a difference, but I've got a Ford 302 motor, generating about 18 mmhg, plenty of vacuum for the booster.

Does anyone have any thoughts or ideas as to what might be going on? My only thought now could be a faulty master cylinder, but I'm 90% positive the seals are totally good there. Thanks in advance!

2 hours ago, solly said:

Originally, I was having an issue where I would brake, but require a bit of pumping to slow down at higher speeds

2 hours ago, solly said:

I replaced the booster with a new one from Zcardepot, and bled the brakes and master cylinder.

2 hours ago, solly said:

When I bleed the brakes, the pedal goes all the way to the floor, but once the system is closed up, I have extremely minimal pedal travel, with not much braking pressure

It would help to be more specific on what "bleed the brakes" means. Are you saying that with a bleeder valve open the pedal will go to the floor and squirt a bunch of fluid? That would mean your pedal and MC are working as they should. The booster just adds force on top of the MC pistons. Does each caliper squirt the same amount of fluid with the same amount of pedal travel?

When you say not much braking pressure do you mean the car does not slow down? Even though the pedal is pushed as far as it will go?

It sounds like the hydraulics are working correctly but the pads aren't creating enough friction. Any chance you got some silicone lube or grease on the pads?

I'd also take a hard look at the proportioning valve. If it's set for too much rear bias you won't get much stopping power from the fronts.

Good luck. Interesting problem.

Or, ignore all of that and assume that you have a bad booster. Maybe put the old one back on if you still have it. Also, check your check valve in the booster vacuum hose. Make sure you're actually pulling vacuum at the booster nipple.

Just now, Zed Head said:

It would help to be more specific on what "bleed the brakes" means. Are you saying that with a bleeder valve open the pedal will go to the floor and squirt a bunch of fluid? That would mean your pedal and MC are working as they should. The booster just adds force on top of the MC pistons. Does each caliper squirt the same amount of fluid with the same amount of pedal travel?

When you say not much braking pressure do you mean the car does not slow down? Even though the pedal is pushed as far as it will go?

It sounds like the hydraulics are working correctly but the pads aren't creating enough friction. Any chance you got some silicone lube or grease on the pads?

I'd also take a hard look at the proportioning valve. If it's set for too much rear bias you won't get much stopping power from the fronts.

Good luck. Interesting problem.

Or, ignore all of that and assume that you have a bad booster. Maybe put the old one back on if you still have it. Also, check your check valve in the booster vacuum hose. Make sure you're actually pulling vacuum at the booster nipple.

Great questions, When the bleeder valve is open, the pedal does go to the floor and squirts a bunch of fluid. There is the same amount of pedal travel when each caliper is bled (and when the MC is bled)

The car slows down, but it takes more time than usual. There's a chance there is something on the pads, I can look into that a bit more. Would you have any thoughts as to why the pedal goes to the floor when bleeding but doesn't move much when I am actually trying to slow down? My thought is that the low brake pressure comes from the pushrod not fully actuating the master cylinder, but I have NO clue why that's not happening.

Thanks for the help! This is my first forum post, haha.

38 minutes ago, solly said:

Would you have any thoughts as to why the pedal goes to the floor when bleeding but doesn't move much when I am actually trying to slow down?

There's nothing stopping the fluid flow when bleeding, that's why the pedal drops to the floor. The fact that the pedal is hard after bleeding shows the bleeding was effective. All of the air was removed. Before, when you were pumping the pedal you were comnpressing air in the hydraulic lines. Brake fluid is not very compressible, air is.

Overall, really, what you're describing just sounds like a booster that's not boosting. No vacuum source or a mechanical problem internally. The system is designed for the force amplification of the vacuum booster. A simple test for a bad booster is to press the pedal with the engine off and note the distance, then compare it to a press with the engine on. The pedal should sink more with the engine on.

You changed several parts at the same time so it can be hard to figure out which part had which effect. I would first confirm that you have vacuum to the booster. Do the test above or just start the engine and remove the hose from the booster. The engine should rev higher or die. If it does, you have a booster problem. If it doesn't yoor vacuum hose is blocked.

Did you remove the check valve on the booster vacuum line at any time? If you installed it backwards that will cause the problem you are describing.