Brake Problems - Air in lines?

[Zhanshi]

Sorry for the long post, but I recently installed the Budget Baller brake setup and have been getting some strange brake problems.

Some background information:
I have the Wilwoods calipers up front and stock calipers in the rear. I used to have Q45 calipers up front and had similar problems. I currently have an auto brake booster with the 7/8" MC (both have ~116k miles). The front calipers have stainless steel lines and the rear has stock rubber lines.

The problem:
When I step on the brake pedal, sometimes it's relatively firm. However, the remaining time I need to pump the brake pedal once. After I pump the brake pedal once, the pedal is firm. Either case will stop fine. The pedal drops a little too far (but not to the floor) to instil any confidence while braking if I dont pump it.

Last week I went on a spirited drive and noticed that my brakes were pretty hot after I parked. The driver side brakes (front and rear) were radiating heat while the passenger side brakes (front and rear) were cool to the touch. The car does not pull in either direction when I step on the brake pedal. I also noticed that my passenger rear brake rotor still has the cross-hatching from when I installed it new almost 3 years ago. The driver's side rear does not have the cross-hatching anymore.

Yesterday I installed speed bleeders all around thinking it was air in the lines from my last bleed. I bled the brakes, but the pedal still feels the same. Sometimes the pedal is firm, other times I need 1 pump to stiffen the pedal.

The pedal does not drop to the floor and there are no visible leaks from any of the lines or cylinder. The pedal also returns to its normal position in both cases. The pedal also holds firm when I pump the pedal with the ignition off.

Is this a case of air in the brake lines or do I need to upgrade to a larger master cylinder (looking into the 15/16" cylinder) to accommodate the piston sizes up front? Is my master brake cylinder on its way out?

I'm pretty stumped at this point and frustrated with what could be causing it. I've been reading about the possible scenarios and cant put my finger on any one fix. Any insight would help! Thank you!

[cozzmo]

Pumping the pedal to give a firm result suggests some kind of rotor runout/pad knock off that is pushing the pads away from the rotors and you need to pump it to bring it closer.

I would have thought 15/16" would be a good idea to upgrade to in either case, especially when running larger multi piston calipers ?

[Matt93SE]

1. Check wheel bearing condition- look for play in the wheel bearing allowing the rotors to have lateral movement in relation to the caliper. this causes pad knockback and a soft pedal.

2. check slider pins on the rear calipers, or look for siezed pistons on them

3. make sure the lines are hooked up properly to the master cylinder. all of your braking on the left side of the car sounds fishy- especially with new calipers up front.

4. this may take more testing than you have tools for.. start the car and put a constant 100lb load on the brake pedal. measure hydraulic pressure at each caliper by removing a bleeder screw and plugging in a 1500psi gauge. check to see that pressures are equal side-to-side, but that the fronts are higher than the rears (assuming you have above 500psi at the front calipers. below about 400psi or so, front and rear hydraulic pressure is the same.)

some of this is mentioned in the FSM, some of it is just 'brake knowledge'. but chek through the FSM for these issues as all of that still applies even with aftermarket brakes.

[Zhanshi]

Thanks for the quick replies!

I'll check the wheel bearings again today along with the calipers sticking. I actually changed out the front bearings about 3 weeks ago. I have peak performance 5 lug front hubs and one hub had 0.03" of play in between the bearing and the C clip. I pressed in new bearings with bearing retainer liquid so the bearing doesnt shift.

Hopefully the lines are in the right place, I believe that is the original master cylinder. Time to trace the lines.

Thanks again!

[0wn3r]

I would assume when you were bleeding that fluid was coming out of the passenger side lines and not clogged up as well. Dunno, just a thought.

[BeerBringer]

Simply a to small MC? 7/8 is Nissans smalest cylinder. Try a 1" or even a 17/16" one.

[Zhanshi]

Just replaced my MC with a 15/16" one. Brakes feel great now!

While replacing it, it found out that the wheel bearing was shifting again. I think the heat destroyed the bearing retainer I put around it. I cleaned it up and put more bearing retainer and pressed it back into the hub. Seems to be holding up for now.

Thanks again everyone!

[Def]

Just replaced my MC with a 15/16" one. Brakes feel great now!

While replacing it, it found out that the wheel bearing was shifting again. I think the heat destroyed the bearing retainer I put around it. I cleaned it up and put more bearing retainer and pressed it back into the hub. Seems to be holding up for now.

Thanks again everyone!

That bearing mount wont work there. Id replace that whole hub NOW.

[Matt93SE]

Yup. tons of force on those bearings. when one bearing goes, it ususally damages the hub too and as soon as it starts moving relative to the bearing, it's shot. you can't fix it without black magic on those bearings. better to replace the hub and move on.

[Zhanshi]

Ah, got it. Any decent hub recommendations?

The quality control of Peak Perfomance was kind of lacking with the 0.03" gap from the c-clip :/

[Matt93SE]

OEM for the hub is your best bet unfortunately.