Brake bleeding FYI / rookie mistake

1990 XJ, 4.0 non-ABS. Ok, so I was replacing some carrier bearings in preparation for a wheeling trip when I realized my calipers had seized up over the winter. Naturally, I replaced both with a new set of pads and had a grooved rotor turned to boot. All is good. Bled the brakes 'till I didn't get any more air, but never could get a firm pedal with the engine off. Ok, this is odd. Took the rears apart, got them adjusted (they were WAY out), checked for leaks, broken parts, etc... all should've been good again after adjusting them. Tried the pedal again... no luck. Dug a little deeper into the issue. Discovered the brakes could be "pumped up" and would hold pressure as long as my foot was holding down the pedal, but as soon as I'd let off the pedal for about 3-5 seconds and push down again, the pedal would go all the way to the floor. VERY odd at this point. Did some research, figured it must be the MC bleeding through itself. Changed it with a reman, bled, bled, bled some more... still no luck. Long story short, both of my new calipers were made for passenger-side applications... meaning the bleeder for the driver's side was located on the bottom of the piston... meaning mass quantities of air was trapped in the caliper. Didn't wanna mess with taking back a perfectly good caliper, so I un-bolted it, flipped it over so the bleeder was on top, cracked it open, and gravity-bled the air out. Brakes work perfectly now.

Just thought I'd post up in case anyone runs into a similar issue. Don't rule out the simple stuff until you know for sure!

How did you just flip it over? It should only go one there in one direction unless I'm completely missing something.

Lowrange2 said:

How did you just flip it over? It should only go one there in one direction unless I'm completely missing something.

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Maybe he flipped it when bleeding the brakes and then turned it back around? I was wondering the same thing.

MagicNelson said:

Maybe he flipped it when bleeding the brakes and then turned it back around? I was wondering the same thing.

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That would make sense.

Sounds like he unbolted it and positioned it with the bleeder up top while just hanging from the vehicle, cracked the bleeder open and let gravity do the work. No pumping of the brakes required. I don't know how effective it is vs pumping the brakes, but I do generally start by just gravity bleeding the fronts if I've had the system opened up for something.

Great job catching that, most people would have not seen that. I have always gravity bleed my brakes. I was told when i was a kid to do this(over 40 yrs ago). My father was a lot smarter than i gave him credit for.

Gravity bleeding is one of my favorite services to do. Once the 12 pack is done, brakes are bled.

I have done the same exactly thing... but I noticed putting it on (was broke and my only spare was a drivers side, I needed a passenger side) so I just held it upside down and gravity bled it. Worked fine till I had money to put new calipers on it, would have worked longer than that but I was doing a ton of other work on the brake system and figured it was the right time since I'd only have to bleed the brakes once.