Brake pedal goes to floor intermittently

[stangsteeda]

Hi guys, I have a 2001 Sport 2wd with manual transmission. I just finished a Springtech 3" spindle lift and discovered my brake pedal goes to the floor only occasionally. When this happens they can usually be regained by pumping the pedal.
To accomplish the lift I replaced the factory 12" rotors with new 11.25" rotors and reused the stock calipers and pads so no bleeder screws or lines were opened. When I unbolted the bracket holding the hard line from the frame rail I carefully secured it lower and wrapped vacuum tubing over the part of the hard line where it contacts the frame rail. I have jacked the vehicle up and looked to ensure the brake lines are not overstretched or pinched and they look fine. Also the fluid level looks good, the ABS light is not on, and there are no leaks that I can see. This also is not really a problem that occurs under full lock steering as some people have experienced it happens at any steering position.

Thanks, in advance.

 

[stangsteeda]

Ok after going out on another test drive I discovered the trigger of the problem. When I turn full lock steering (either right or left) my brake pedal will go to the floor. It can be regained easily by straightening the steering and pumping the brake pedal once or twice and then my brakes are perfect again.

I am going to jack up under both lower control arms so the vehicle will be at true ride height and turn the wheels lock to lock as I double check the brake lines in these situations.

Thanks in advance.

 

[410Fortune]

check for leaks in the brake booster vacuum hose and fitting

If the master cylinder (pedal) is going to the floor it points to either air in the brake lines or the seals in your master cylinder are failing, but first check the booster for vacuum

 

[Cobraguy]

but why only when the wheels are fully locked? Puzzling. If the booster loses vacuum, the pedal shouldn't go to the floor...just get hard. But I do believe Jamie is dead on about the master cylinder. I had a race car that did this to me twice. Both times it recovered by pulling the pedal back up. I replaced the master cylinder and it never happened again. But why this does it at full lock is something that needs to be investigated. I will really be interested in seeing what you find. First things to check would be your brake lines at full lock and see if something is binding or stretched.

EDIT: Just a thought...this hasn't been converted to a hydroboost has it?

 

[stangsteeda]

Hi guys, I discovered the problem. When checking all clearances I missed the little balls on the lower control arm which as I believe serve as steering stops with the stock spindles. Well under those full turning situations the little ball would depress the caliper in a way to press the piston back into its bore. So then it is like when you replace brake pads and have to pump up the pedal to get the pressure back.
I took the side grinder to the little things and all is well now.

Thanks guys for helping though.

 

[Cobraguy]

Wow!

 

[410Fortune]

do you not have stock spindles?

I dont like taking my 4x4 trucks to full lock unless I have to
I know the steering stops on my 88 BII with a 93 front end are toast, so I dont turn that far
I know the CV's on my explorer will bind at full lock, even in 2wd it gets stiff, so I dont turn that truck that far either

I would love to see a pic of what you are talking about, I am having a hard time picturing it in my head! LOL
Especially a pic of your grinder fix


Nice work! Having a look see at the parts, checking clearances, for binding, and looseness is always a great way to diagnose instead of just buying parts