Mystery Brake Issue

[Tbullet]

Need a little insight on a brake issue I am having. When i initially press the brake pedal it is a little soft/squishy. The second press always is firm and seems to be okay.
If i open the brake fluid reservoir it equalizes in pressure. Can't tell for sure if it's a vacuum or compressed. Either way, my brakes perform normally until it sits overnight and then rinse and repeat.

Any ideas on what this could be and how to resolve it?

Cheers

 

[AK Wes]

Did you try bleeding your brakes yet?

 

[Tbullet]

Did you try bleeding your brakes yet?

Yup. Twice.

 

[AK Wes]

Yup. Twice.

Hmmmmm...... This really does sound like an issue with air in the brake lines/hoses somewhere, but it could be another issue since you have already ran through two bleed cycles. I hate to throw money at problems, but if it were me I would start contemplating new brake bleeder screws and hoses. I'm not sure if you have replaced those recently or if they need to be replaced. You could have a really slow leak happening somewhere that isn't registering in your brake fluid reservoir just yet.

Just trying to throw some ideas out there. Let us know if you find the culprit!

 

[2001LC]

Did it do this before bleeding.
Did you Time Test that accumulator motor stops within 30 to 40 seconds.
Over 40 second, FSM states re-bleed. But this is often due to a bleeder or two weeping (leak).
Did you go out a drive on dirt road and active ABS hard three time. Then re-bleed if over 40 sec and no leak found.

Over 40 sec., also seems to happen after a master rebuild sometimes, but corrects itself within a week or two usually.

The accumulator bleeds down as vehicle sits with key off. So when you first get in and step on brake as you insert and turn key to on, peddle my go further at first, until pressure builds back up.

Note: Dry brake fluid out of bleeders with compressed air. Keep good rubber bleeder caps on, once dry.

 

[TXLX100]

There is a thread here about master cylinder rebuild. There is some debate / conversation about adjusting the master cylinder piston v rebuild that will improve the symptom. I had the same issue and replaced piston and a few other bits (prob not needed), and fixed the soft pedal.

 

[Vermont]

I had similar symptoms to you - It was a pin-hole leak on a line, wasn't enough to drip constantly, but was enough to lose pressure in the system over a short period of time.

 

[Maxxer]

I also had similar symptoms. Bled brakes multiple times, no difference. Replaced pads, a little better. Finally adjusted pedal free play and no more soft pedal after setting for awhile.