How does the bomb (brake accumulator) work and what's the ppurpose?

holds pressure for using the brakes when the motor isn't running
 

The brakes in these cars have a hydraulic assist system, instead of the normal vacuum booster type. therefore, if the engine is not running, the hydraulic pump is not running, and there would be no brake assist (say, if the car died on the highway and you still needed to stop). The bomb accumulates pressure while the motor is running, and uses that pressure so you can still have full brake assist with the motor off. It also slightly improved brake feel when I changed it on my car.

So weak bomb shouldn't affect braking power when engine is running, right?

According to SJM it does give hydraulic assit during initial application.
 

<ul><li><a href="http://www.sjmautotechnik.com/trouble_shooting/brake.html#bomb">http://www.sjmautotechnik.com/trouble_shooting/brake.html#bomb</a</li></ul>

hydraulic reservoir they are talking about is power steering reservoir, right?
 

As SJM desribed my brake light comes ON when engine is turned on and goes away within 1 minute. And it takes ~30pumps on brake pedal to make it hard to press, so bomb is ok then.

Ahh, me too.
 

I have heard a rumor that flushing your system with Pentosin and cleaning the small screens in the lines helps the bomb properly build pressure.

My car acts exactly the same. I get 22+ (lost count) pumps out of the pedal, and the brake light will go out immediately if the car has been running any time in the previous hour.

When I install my FMIC, I'm planning a hydraulic system flush. I hope that cures my problem.

It also effects the braking while the engine is running.