Lost Stopping Power

[maytag]

You're one of the smarter guys on this board, so I scratch my head trying to imagine something you wouldn't have already thought of. But I'll suggest some things I'm thinking, in the hopes it'll jog a thought.

Does your car have PSM?

RacerBoy and JayG seem to be thinking along the sames lines as I am: "Glazed pads". What pads are you using, and did you heat them (coming down a conyon, or?) prior to the symptoms appearing. I've been known to "deglaze", when my budget required it. Use a palm sander on the pads and even on the rotors. You're not trying to change the shape, just remove the top glazing that's there. Organic pads are notorious for this. (I've done the same with clutches, fwiw)

Do we understand correctly that this more or less happened "overnight"? and your fluid flush was done to mitigate, not done before, right? I ask because a mis-mix of brake fluid can cause obstructions in the master-cylinder or the lines or the calipers. (DOT 5 doesn't mix with other fluids, for instance,and will create nasty gel in the lines) You hadn't topped-off the fluid recently, or anything, right?

From there, I think I'd be pulling all 4 calipers, inspecting visually, probably cleaning thoroughly, maybe a seal kit if there's one available (I assume there is, they're Brembo) and then this is where scope-creep would take over: I'd be doing pads, rotors, steel-braided lines, etc. Then a complete flush. That oughtta do it, haha. (Sounds like a fun winter project?)

[maytag]

hmmm.... another idea. Spray a light mist of red spray paint on your rotors, then go out and ease into the brakes gently, even just in the driveway, and then get out and look at what paint remains vs what's gone. You'll get an idea about pad-to-rotor contact.

[particlewave]

Originally Posted by maytag

hmmm.... another idea. Spray a light mist of red spray paint on your rotors, then go out and ease into the brakes gently, even just in the driveway, and then get out and look at what paint remains vs what's gone. You'll get an idea about pad-to-rotor contact.

I like this. Between it and the temp gun, I should be able to determine if one wheel is grabbing more or less than the others.

No PSM and car is a ‘99.
“Overnight” isn’t exactly right as I don’t drive it daily, but it was fine one day and had this problem the next time I drove it (noticed on first brake press when backing out).
I suppose it could be glazing, but I haven’t driven it hard in a while. The way it feels and my gut are both telling me it’s something mechanical, though...

The flush was done after the issue cropped up. It didn’t seem like a fluid issue, but it needed to be done anyway (I may have imagined the slight improvement after fluid change). The reservoir had been opened around the time the problem began to check the fluid moisture level, but nothing added.

I haven’t had much time to address it because of the move. Now we’re here, the weather has been great, and I can’t drive.
I hope to have time to hit it hard soon and get it solved.