Brakes lock up over time?

NEED_FUMES

MEMBER
2005 HONDA PILOT
3.5L
V6
4WD
AUTOMATIC
217,000 MILES

Initially, I had a spongy brake pedal. I replaced the master cylinder and bled the brakes. Still spongy, so I changed the brake booster. It got better, and I could stop with ease.

To put on the cylinder and booster, I had to move some ABS lines out of the way, but I put them back on and bled the whole system as standard.

After going through a drive-through (engine running 20 minutes from house to drive-through), the brakes drag and finally lock up. Hot brakes and high RPMs to get off the road. The brake pedal was tight and did not have the normal give that would be in the brake pedal. I had to pull the booster vacuum tube to get the brakes to work correctly and get it home.

I do not see an adjustment for the booster pushrod (rebuilt from napa) nor an adjustment for the master cylinder pushrod (new from amazon). I have looked in many manuals and cannot find an adjustment as the brakes drag and then lock up when the engine or brake fluid is warm.

Is there an adjustment for the brake booster or master cylinder pushrod to account for manufacturer tolerance differences?

What would cause the brakes to lock up over time, maybe a bad portioning valve in the booster not letting the boost drain when not in use?

1 Reply

KEN L

MASTER CERTIFIED MECHANIC
47,643 POSTS

I would replace the brake booster and master with high quality parts, which is the problem with aftermarket, they use internal parts that don't work, you can confirm the booster or the master by loosening the brake master mounting bolts two turns and the brake should release. The problem is either the booster is not allowing the master to return to the neutral position, or the brake master does not have a strong enough return spring internally.

This guide can help explain:

https://www.2carpros.com/articles/a-comprehensive-guide-to-fixing-automotive-brakes-locking-up

Please go over these guides and report back.