Very soft brakes after re-attaching caliper

When I drive over bumps it sounds like there's a bag of rocks under the hood. I talked to my mechanic and he said to check the rubber bushings that wrap around the 7mm bolts that hold the caliper on. Sure enough, they were all missing or falling apart, allowing the caliper to rattle around. So I this morning I replaced them with brand new ones, and---woops--now I've got almost no brakes! I can put the pedal to the floor and I still roll to a gentle stop. Not good.

Here's the exact steps of what I did:

1. Unbolted the wheel and removed it.
2. Removed the 7mm bolts that mount the caliper
3. Took the caliper off the disk and cleaned out the gunk inside the two mounting bolt holes
4. Greased the inside of those holes and slid the new bushings in.
5. Wrestled the caliper back onto the disk.
6. Tightened down the 7mm bolts.
7. Bolted the wheel back on.

I never detached the brake hose leading to the caliper, and I was careful not to disturb the little nipple/port (which I assume is for charging the system). What did I do wrong to loose all my braking pressure? (and how to I fix it?)

Thanks as always!
 

Assuming its correctly assembled,  pumping the pedal a few times might restore the hard pedal.

I agree that the pedal needs a few pressings after any work to reseat them and re-pressure the lines.

Also you may want to bleed them prior to any more changes.

abfmk1 I test drove it around the block which meant I probably pressed it ~4 times. Should I do it more? The brakes felt fine before I messed with the bolts, and I didn't actually disassemble anything so I'm confused how they got soft.

Briano1234 Can you say a few words about why it needs a few pressings to get re-pressurized? I thought that it was a closed system, and so I'm surprised that me moving one of the parts around (without opening the system) somehow caused it to lose pressure.

Is the pedal soft because I somehow got air into the lines?

I fired it up and did a quick test. After a few more pumps the pressure DID build back up… but then as I kept pumping, it seemed to decrease.

After a few pumps it stiffened up. But after that, if I press the brake hard, it will slowly let me push the pedal to the floor. It may have always done that (even before I fiddled with the caliper) but I can't be sure.

It sounds like I need to bleed the brakes… but I'm still confused about what happened, since I never opened the lines.

What happened was that parts moved, and it takes a few pumps to get everything back in its ready to work position, quite normal when brakes are disturbed even if the lines are not opened. A bleeding session does sound like a good idea.

Got it. When everything is set up correctly, should I be able to gradually press the pedal to the floor like I described above? Fortunately, I haven't had much reason to notice that during my normal daily driving. ;-)

I bought a cheap brake kit and bled the system. Now they feel much better! Still a little soft, but it might just be that I'm paying closer attention than ever before.

The pedal shouldn't travel to the floor.

If it does there's a leak somewhere or air in the system.

If it's still doing it you may have a leak on the master cylinder. Keep a close eye on the brake fluid level  

Ian

borednow Is there an easy way to determine whether it's a leak or air in the system?

I don't see brake fluid squirting around under the hood, but a tiny pinhole along any of the hoses would produce the same results, right?

A leak can be internal, ie fluid leaking past a seal in the master cylinder but not escaping the system so no fluid is actually lost.

Air will generally give a spongy feeling to the pedal when pressed hard, whilst with a leak, the pedal feels reasonably normal but will sink at a steady rate, under consistent pressure, all the way to the floor, the rate of sink being proportional to the size of the leak.

It is also possible that dirt entered the system, or existing dirt within the system was disturbed and is now preventing a seal from doing its job properly.

If bleeding the system helped, it may be that further bleeding may help and if the fluid is over 2 years old it should be changed anyway. I highly recommend the gunsons pressure bleeder to achieve both, it's not expensive and does a great job at both with relative ease. It will also help flush out any dirt that may exist in the correct direction thru the system.

"the pedal feels reasonably normal but will sink at a steady rate, under consistent pressure, all the way to the floor"

^ This definitely matches what I'm experiencing. :-/

What you said about the dirt in the system is interesting.  The two front bleed ports didn't have the little protective rubber caps on top of the valve. I tried to clean out the nozzle a bit with a small pick but I did see a small cloud flush through the tube when I was bleeding out the fluid. I wonder if some of that got under the valve cap and isn't letting it close all the way… if this were the case would I expect to see a dribble of fluid around one of the valves? I'll check.

I'll try bleeding it some more too. I thought I got all the bubbles the first. I followed instructions in another post that say to start at the rear passenger brake and work towards the master cylinder. But I was working alone so I could actually see the fluid passing through the tube into the bottle.

The fact that you got bubbles show that you likely did have air in the system (not definitive, as if the bleed nipple is loosened enough, or in poor condition, air can be drawn in past the threads and expelled thru the tube making it look as though there is air in the system), so bleeding again will certainly do no harm.

Dirt in the system will generally only cause an internal leak if its present in the master cylinder i.e. dirt on a seal between two areas of fluid. Dirt elsewhere, if causing a leak, will be expected to cause an external leak.

^ Yeah, what Morr said.  

Bleed again and if you're still getting the drop to the floor change out the master cylinder  

Ian

morr said

The fact that you got bubbles show that you likely did have air in the system (not definitive, as if the bleed nipple is loosened enough, or in poor condition, air can be drawn in past the threads and expelled thru the tube making it look as though there is air in the system), so bleeding again will certainly do no harm.

One Big reason that I advocate wrapping the Bleeder ports with Yellow PTFE tape.  Keeps them from Rusting up, then using a mighty-vac it won't suck air in the bleeder threads.  

The MC's are also known to leak from the Pusher seal into the brake booster, so if that happens you will get a soft pedal and Fluid in your booster that you ned to clean out.

When replacing the MC, Take your time.  Take each bolt down together 5 turns on one 5 on the other failure to do this can cause the Pin on the Booster (if installed) to become dislocated from the booster fingers, then depending on how it separated you may need to source a new booster.

Briano1234 said

One Big reason that I advocate wrapping the Bleeder ports with Yellow PTFE tape.  Keeps them from Rusting up,…….

An excellent tip from Brian, I must do that myself next time.

On that point, whilst using a pressure bleeder vs a vacuum bleeder is largely a matter of preference, I do prefer the pressure bleeder as amongst other differences it greatly reduces the possibility of air being drawn in via the threads in the manner mentioned previously, when compared to a vacuum system.

morr said

 An excellent tip from Brian, I must do that myself next time.

On that point, whilst using a pressure bleeder vs a vacuum bleeder is largely a matter of preference, I do prefer the pressure bleeder as amongst other differences it greatly reduces the possibility of air being drawn in via the threads in the manner mentioned previously, when compared to a vacuum system.

Which is why I too use a power bleeder of my own making, as I don't need a 2nd person (momma) who takes exception when I as for her assistance.