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Old 01-24-2008, 08:10 PM   #1 (permalink)
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Brakes, EOC (engine off coasting) and reserve vacuum

I don't EOC but have in the past and I've found that with the motor off, the power brakes have 3 pumps before you lose them and revert to manual. I also found that if you make a brake application and don't release the brake all the way but just enought to stop the slowing that you won't run out of vacuum for quite awhile and can make multiple applications with no problem. Has anyone else try this or want to verify it. On a deserted road of course. So far It works for 2 of the cars I have driven. It might help with the EOC discussion and safety.

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Old 01-24-2008, 08:17 PM   #2 (permalink)
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I've experienced similar to what you describe. 2 applications in my car feel fully assisted with the engine off.

Another technique some people use if they just need a little braking while coasting but want to preserve vacuum is judicious use of the hand brake (holding the button in, obviously).

One potential hazard there to be aware of is you don't show brake lights to following cars using the hand brake.
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Old 01-24-2008, 08:21 PM   #3 (permalink)
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The three full applications is standard so far as I can tell.
It seems to be the limit of the vacuum reserve tank on the vacuum booster.

By the way this is an easy way to tell if your vacuum boosted brakes are working without going on the road.
Turn the car engine off.
Press the brake pedal repeatedly (normally about three pumps) until it feels hard. Then start the engine with your foot hard on the brake.
If all is well the pedal should move toward the floor as the engine starts.

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Old 01-24-2008, 08:37 PM   #4 (permalink)
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Just chuck the booster in the trash, manual FTW!
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Old 01-24-2008, 08:43 PM   #5 (permalink)
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The ForkenSwift is manual, and it's OK without boost - but I installed larger calipers & discs from the 4-cyl Swift onto the car.

The Flea is brutal without assist. Much more force is required.

I've read that drilling the booster and puncturing the diaphragm makes unassisted braking much easier, but I've been reluctant to try it on the ForkenSwift in case we're ever told we must have assisted brakes.
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Old 01-24-2008, 09:17 PM   #6 (permalink)
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Huh, I wonder how that works... Maybe when the engine's off, the same mechanism that allows air to enter on one side of the booster to help push against the lower pressure portion pumps more air into the same place, increasing the pressure past atmospheric on what's usually the vacuum side?

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