Noise in master brake.

[Ray Lasick]

When I apply the brakes I get a humming sound form the unit.Why is this happening? What is the fix?Brakes work,but I'am also geting a CHECK ENGINE light when sitting at a stop light waiting for it to change.The engine looses some RRRRRS and shudders. Light will go off when I accelerate from the stop, it takes to the count of 12 to go off.
Are these problems related to each other?
I'am on my third master brake assymbley,the car has 119 on it.

 

[REEDOG]

Hi neighbor. Humming is normal for the powermaster when the brakes are applied. I would ditch the powermaster setup and convert to vacuum. Costs less, fewer parts and it's much less trouble. Mine works just as well. About the check engine light, can you read codes? Doesn't sound to me that the two are related. Start by finding out what code is being displayed. Let me know if you need some help.