Help - 2015 Q70 Intermittent Brake Malfunction

[mikedamageinc]

Well the problem came back and is pretty much daily. I'm not sure what caused it to go away and then come back but i verified that the ground is good. I noticed that other strange behavior happens when the condition is present, abrupt downshifts when slowing, early upshifts, inconsistent throttle (sometimes numb, sometimes touchy). Also while the pedal sinks, if i keep pushing it all the way the drivetrain slightly bumps kinda like when you put it in drive.

[mikedamageinc]

I'm still having this problem. I replaced the master (again, this time Raybestos) and swapped ABS module with a used unit, it felt great all winter but now that its warming up the problem came back. Seems like around 70+ is when it happens.

[VStar650CL]

With a new master and ABS, if the problem is mechanical then the booster is all that's left. Air in a hydraulic system doesn't come and go, and the odds of two ABS's in a row bypassing the same way are pretty slim. Electrically, did you ever pop the ABS connector and check the pin fits?

[mikedamageinc]

With a new master and ABS, if the problem is mechanical then the booster is all that's left. Air in a hydraulic system doesn't come and go, and the odds of two ABS's in a row bypassing the same way are pretty slim. Electrically, did you ever pop the ABS connector and check the pin fits?

Just a visual on the pins, I didnt try bending them or anything but I might give that one more try. I feel like it cant be physical at this point because if it were, the fluid would have to be going somewhere and I have verified it is not at any of the wheels or leaking into the booster from the master. I dont think it could be the booster because it is solid linkage inside correct? Meaning a sinking pedal would have to be physically broken pieces in the booster which would not come and go.

The only thing I can think is that some strange parameters are being met in the electrical system for it to tell the ABS computer that it needs to bypass fluid which makes the pedal drop. Is there any sort of bias valve later in the lines maybe towards the rear or something?

It always stops well, just sinks while stopped, and off pedal back on will usually keep sinking but initial pedal push always feels solid which is nice but any issues with braking could always go south quick. If I could bypass the abs but still be drivable, I would be ok with that at least in the short term, but if disabling ABS puts it into limp mode obviously thats a no go. Otherwise this things about to get sold to car max on a cold day! I also keep hoping someone would run into me but self preservation always makes me avoid the collision, lol.

[VStar650CL]

Getcha some 0.025" music wire and give the female connector pins a proper check. All it takes is one weak or broken spring to cause a world of grief, and usually giving the male pin a 10~15 degree twist with a needlenose is all it takes to fix it.