When I apply the brakes on my 86' T-type, the first few times in the morning, I hear a loud humming noise that seems to be coming from the accumulator ball. I can feel it vibrating a little bit on the ball but not on the powermaster unit itself. Brakes are working fine and brake light hasn't flickered or came on at all. Do I need to replace the accuulator ball? How do you check it? What exactly is the purpose of the ball? Thanks, R.B.
Humming Accumulator Ball?
- Thread starter rb68rr
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The purpose of the accumulator ball is... to accumulate! 
It is filled with nitrogen, under pressure, and the pump under the PM pumps in brake fluid, further raising the pressure. Then, as you use the brakes, fluid is pushed out by the nitrogen. When the pressure drops to a pre-set level, the pump comes on, and refills the accumulator until it reaches another, higher preset pressure. Nothing mechanical in the ball, so it can't really hummmmmm. The noise is from the pump. As long as it stops in less than 20 seconds, you're Ok. If it takes longer, then you need a new accumulator, because the nitrogen has leaked out. Or maybe you need a new pump, but try the ball first. Also, sometimes the pressure switch fails, but usually when that happens, the brake light comes on and won't go off- don't drive the car when that happens, you can ruin the pump, or run into something when the car won't stop!
It is filled with nitrogen, under pressure, and the pump under the PM pumps in brake fluid, further raising the pressure. Then, as you use the brakes, fluid is pushed out by the nitrogen. When the pressure drops to a pre-set level, the pump comes on, and refills the accumulator until it reaches another, higher preset pressure. Nothing mechanical in the ball, so it can't really hummmmmm. The noise is from the pump. As long as it stops in less than 20 seconds, you're Ok. If it takes longer, then you need a new accumulator, because the nitrogen has leaked out. Or maybe you need a new pump, but try the ball first. Also, sometimes the pressure switch fails, but usually when that happens, the brake light comes on and won't go off- don't drive the car when that happens, you can ruin the pump, or run into something when the car won't stop!
Red Regal T
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What's the tune? 
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