Originally posted by Fat Audi 80
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All bombs left for a period of time will slowly leak away their stored pressure but new ones take longer than old ones so if you replace your bomb you'll be able to leave the car longer before you get the "!" warning after 30 seconds but you'll still get it eventually, it just may be only after months of no use with a new bomb.
You get the "!" warning because it's taking your hydraulic (PS) pump more than 30 seconds after start-up to refill the bomb so it's back up full of energy in the form of stored hydraulic pressure to assist your brakes. When your pump gets old it takes longer to refill the bomb especially if you're using the PS at the same time, i.e. manouvering the car off your drive. However, as the "!" warning does go off and as long as it doesn't come on again, then the system is fine. If Audi had set the time limit to 1 minute rather than 30 seconds most folks would never see the "!" warning and the bomb wouldn't get the bad rap it does.
The test of how many brake pushes you can do before the pedal goes hard measures how much energy the bomb can store. That's the one that counts. As long as the bomb can store enough energy to work your brakes, that's what matters, not if the "!" comes on after 30 seconds and then never comes on again.
John
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