TL; DR: This is not (directly) GMT-related (but someone may find it helpful, so... get off my @ss
... LOL)
Tackled the brake issue in the Accord, after receiving a nice flaring tool, a tubing cutter, and a reamer from Amazon. Had a credit plus some Amex points, so it ran < $20 USD. After it arrived, I found the 'conventional' type flaring kit I'd bought from HF on a closeout and stashed away. Oh, well... free returns with Prime (btw, I heard on the news that Prime is going up another $20, soon... to $139 USD)
Jacked up all four ends and put the whole car on stands. Couldn't find a leak anywhere.
Hard lines looked ok (Honda coats the lines, and additionally covers the exposed / bent ends). Flex hoses looked OK. Dry, no swelling / ruptures. And yet, the fluid reservoir was dry as a bone.
Filled up the reservoir, which took about half of a quart. A lot of fluid, considering.
No leak in the reservoir or line connections. Lines to the VSA module looked OK, as did the module.
Pumped the brakes expecting to see some fluid escaping somewhere, and... nope. Still dry.
Brake booster looked OK. Bled the front calipers. Still dry. Moved to the back... if the front is OK, it must be in the back, right?
Moved one of the rear tires out of the way, and saw the back side of it. Why was it still 'wet' in spots? It had been in the garage for days, now.
Then it hit me...
When I did the brakes last year, I replaced both rear calipers, as the parking brake was inop, and one caliper had frozen (a common problem on Hondas). I actually use my parking brake, and my Accord has the M/T, to boot.
(fyi, with Hondas and many Asian vehicles, the parking brake is cable-operated, but the cable moves a lever that turns a circular disc that, in turn, then pushes the caliper piston against the disc. Sounds complicated, but I'm really just pointing out that it works a bit differently than the 'drum-in-hat' parking brake we're used to on the GM trucks. Anyway... )
When I compared the old / new (reman) calipers, I had noted that the supplied new washers that go on either side of the banjo bolt were smaller in O.D. and made of copper, while the existing OEM were aluminum. So I decided to reuse the OEMs, as they looked to be in good shape.
That was my undoing.
Even though I torqued the banjo bolts to 36 ft-lb, and didn't see any leakage when I bled the new rear calipers... they eventually leaked out. Took the better part of a year (I don't drive the car everyday), and I didn't notice any gradual degradation in braking (having an M/T contributes to this, as I use the brakes way less, vs. with an A/T)
The front calipers weren't changed out, so that explained why I didn't have any leakage there.
But both rear tires had some wetness (brake fluid) on the inside sidewall. One was way worse than the other, but both had the telltale spots.
Looked up Honda's part for the washers... and they're selling for about $6-7 USD, each. For one 10mm flat washer! (2 are needed for each caliper)
Hmm... $28 and a two-day wait (or even more expensive from the local dealers)... or sub-$10 for four of the correct sized ones in copper, 15 min away at AAP. I picked the coppers. Will put them on tomorrow, bleed, and check the banjo connection thoroughly, this time. And I have to run a diagnostic cycle on the VSA module afterward, but I don't expect it'll cause me any trouble. I have a decent scanner for the Accord (not a factory tablet, but still pretty good).
If they leak again, I'll bite the bullet for the spendy Honda washers, since now I know what happened, it's not an extreme pain to redo them, and I'll now keep a closer eye on the fluid reservoir for a bit, to make sure the hydraulic system is intact. The only thing that bothers me is that the loss of pressure was really binary -- pedal felt fine... until it didn't. Another reason to keep a closer eye on things until I'm
sure everything's good.
Was reviewing an 'Eric the Car Guy' video today, and he mentioned himself that while it's technically a no-no to reuse the washers, he thinks re-using the OEM is preferential to using aftermarket coppers. Was nice to see we thought alike, given how by the book he is with Hondas (I've watched him go on rants about things like not reinstalling the brake rotor hold down screws (that most times, have to be drilled out, anyway). I like Eric, but sometimes he can be even more anal-retentive than me.
And with that, the mystery of the squishy brake pedal is resolved.