2011 Toyota Sienna XLE, 120k , Automatic, Had Code C1441 (Pending),Cleared code but hasn't returned (yet).
Issue: Brake Sinks to floor when the engine is running.
My initial thought was a bad master cylinder, So replaced the part.
Bench bleed the MC, manual bleed brakes.
Problem remained.
Used computer (techstream) to air bleed braking system (and ABS module)
Problem remained.
Brake pedal is hard when the engine is off.
The Brake pedal gets harder when the engine is off and brakes are pumped. Figured the replacement MC is good.
The vacuum check valve is good.
No apparent leaks anywhere. No Fluid loss. (before or after the MC swap)
Car does stop, but not until brake pedal is near floor.
My typical experience with Brake Booster is if they are bad, the pedal is hard to press when the car is running or not, but I am having the opposite issue.
My experience with bad Master Cylinders if if you hold down the brake with the engine off they usually sink. I'm not having this issue.
Wondering if this is a sign of a bad brake booster or something else.
Thanks for your advice. Love your videos!
Much Appreciated!
That is a weird one, my thought would maybe be the ABS module. I have heard that the seals can go bad in it and can blow by under high pressure.
I ended up replacing he ABS module as suggested as well as the Brake Booster, I rebuild the calipers (even thought there was no leading because they needed new dust boots anyway). Re-blead the brake. Firm peddle that does not sink when the car is not running. Once the car is started there is no pressure at the peddle (goes to floor). when the car is turned off and brakes are pumped to release vacuum, the peddle become firm again and does not sink.
Summary of work done: Master Cylinder replaced, Brake booster replaced, all 4 calipers rebuilt, rotors replaced, ABS unit replaced with used unit. System air bleed using TechStream. No air is coming out of the bleed screws at the calipers.
Any further ideas of what might be going on here and how to resolve?
Also no leaks identified. Fluid level remains stable.