It's been about 2-3 weeks since swapping the front calipers (in addition to rotors, brakes and some front suspension components while I was at it) in my 1995 Accord. I drove it a bit around town, and the brakes felt great! Afterwards, I was only concerned about having tightened the nuts on the suspension components adequately, and I previously posted on that. I think those issues are resolved or mostly resolved at this point.

Last Wednesday, I took my car in for inspection and it passed. However, on Friday, driving into town, I found that my brake pedal went nearly to the floor upon stopping. I didn't drive it Thursday, but my husband said his experience was the same. I was actually wondering at the point if the inspection process opened up some leak, but would rather know now than when I have kids in the car driving on the highway!!

At any rate, I took the car into my garage, fearing that maybe I had destroyed the master cylinder when bleeding brakes after caliper installation, even though I took extra care and put a block under the pedal and so forth. The brake fluid level still says it's full--maybe it's a bit lower, but hard to say. I had also cleaned the ABS sensors when installing the calipers and for the first time since I've owned it (bought last year April), the ABS modulator doesn't run for a minute upon starting before faulting.

I did add some fluid to the ABS reservoir, mostly because I couldn't see the level, but evidently it was full from the start...didn't take any additional.

I did NOT bleed the ABS unit because my Hayne's manual states you only have to bleed the wheel where you change the calipers... so in this case, both front ones...even though a full proper system bleeding would start at the right rear, left front, etc.... If I had had more time (needed vehicle the next day), I would have cleaned the garage so my entire vehicle would fit, changed out the rear rotors, pads and whatever else, and bled the system, but at this time, I had only the front end in the garage on jackstands. Nonetheless, for the time it seemed adequate.

So on Friday, my thoughts were... is it the master cylinder? Is it related the the ABS unit now that it's faulting out much less (sometimes not activating the light at all during a trip out, and sometimes only after a while). Is there a leak?

Saturday, when I pulled the car into the garage (with caution, worried brakes would fail and I'd run over stuff...put car in low gear to drive in), I turned off the ignition, pumped the brakes and the pedal acted normally, rising with each pump.... then held the pedal down for over 30 seconds, maybe even a minute, and the pedal remained firm at top.

So... I'm thinking it's not a problem with the master cylinder, right?--because if it were, the pedal would sink to the floor as fluid flows back into the reservoir, so I understand. I was perplexed, but was a little relieved, thinking all I need to do is bleed the brakes, figuring maybe I didn't get all the air out, though I would have expected the problem to surface sooner.

Sunday, when I had a little more time, I took all the wheels off, looked at the rear suspension components, where all looks fine... then went to gather tools to bleed brakes, not yet seeing time to do rear brake rotors and pads as the car would be needed today. I found that the rear bleeder valves would need to be replaced...seemed like the calipers were probably fine (couldn't get light where I needed to view the brake pad behind the one rotor)... but then:

I saw an ever so slight liquid stain on the top of the rear passenger caliper. It's maybe damp, not entirely sure. Definitely not a puddle or drop that is clearly new. But it's under the one rigid brake line that goes over the caliper, where it attaches to the flex line containing the banjo bolt to the caliper. It's notable that the brake line DOES have flaky rust on the surface but no visible hole (scraped at the exposed segment with my finger nail), and when I wiped it with a paper towel, it seemed to have some very slight liquid residue and dirt. So I thought I found my problem...though not sure if I have to order the piece from Honda or what....

Anyhow, now I just went out to the garage to see if there are any stains on the floor, put paper towels under the rear wheels, went into the car and pumped the brakes and held them down a few times....and there is no new liquid residue or film, nor any liquid on that line itself.

Is it possible that my line has developed a leak so minor that it cannot be detected upon observation, yet enough to let air into the system over time? Is it possible that the inspection process let air in that now needs to be bled? Is it possible this air was trapped from before and is now in a compromising area? Could it be that this particular spot isn't actual a compromise but some other spot is...with no stains left on the floor?

Yes...mostly, I want to know the best way to proceed from here. Right now, I'm going to go put on the new rear rotors and brake pads... if I find calipers to be damaged, then I'll replace those as well.

I can't bleed the ABS unit myself, but can do that tonight when my husband gets home, and proceed to bleed the system in proper sequence UNLESS I should be doing something different.

Any advice is appreciated!

 

I would start with a fresh full system bleed but also check the interior cabin for leaks from the MC.

 

I'm going to summarize the above a bit--don't mean to write a book, just type fast!

PREVIOUSLY
Last month I replaced the front calipers, rotors, brake pads, some front suspension components and the front wheel bearings, after experience brake pad grinding that is associated with bad calipers. My car had no other symptoms.

Of course, I bled the brakes after all was done, and happily drove my car around for 2-3 weeks. Car passed inspection last Wednesday. Brakes were failing Friday.

I propped the car on jackstands for 2 days, noticed a slight stain on rear caliper (maybe leak source? Don't know), wiped it clean... no drips or leaks appeared on floor. I followed up above...did not notice leaks in interior, but will check again, just since lighting is bad at night when I work.

LAST NIGHT
Cleaned up rear bleeder screws (that were plugged) and bled system last night, including ABS reservoir. Did not notice any air in system, though admittedly, there could have been some escaping rear bleeder screws, since I had to remove them to unplug them. I did gravity bleed those calipers for a bit... but no air seemed to travel through the clear line.

TEST DROVE CAR last night and it seemed good to go.

TODAY
My husband drove the car to work...and he has to travel a bit to appointments. I called him midway through the day and he said he hadn't driven a whole lot but didn't experience any problems at that point. When he came home, he did mention that he felt the car creeping forward slightly at a stop light, but he didn't have his foot on the pedal hard; pressing down stopped the forward motion, but...

I'm now thinking that it IS the master cylinder at fault? Any tests I can do?

 

Besides checking for leaks I am not aware of any, and if you are visually inspecting it off the car might as well replace since they are inexpensive enough.