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I have a GS400 1999, booster pump is operating all the time.

I have a GS400...

I have a GS400 1999, booster pump is operating all the time

Mechanic's Assistant: Have you checked the fluids recently?

Yes

Mechanic's Assistant: What is the model of your '99 Lexus?

GS400

Mechanic's Assistant: Are you fixing your vehicle yourself? What have you tried so far?

Yes, code c1251, c 1256 and c1223 showed up and I bought a used master cylinder assembly with accumulator and pump and replaced the existing one no codes are popping up but the pump connecting to the hyd accumulator is running all the time

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

Is the issue due to low pressure in the accumulator?

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Customer reply replied 3 months ago
brake is fully functional and no leaks
Answered in 2 hours by:
3/26/2018
Pete
Pete, Mechanic
Category: Lexus
Satisfied Customers: 139
Experience: Ase Master Tech
Verified

If the problem happening with the used mc unit I would suspect the accumulator is the problem. The internal seal is ruptured and the pump pressure is bypassing inside the accumulator and not allowing the system to build enough pressure to trigger the pressure switch to turn the pump off.

Pete
Pete, Mechanic
Category: Lexus
Satisfied Customers: 139
Experience: Ase Master Tech
Verified
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