The brake pedal has started emitting a slight "hiss" @ the firewall. This stops when the pedal is depressed slightly. I'm guessing the air booster has a small leak but not a critical safety issue? Does that sound right? Is there a easy fix? Thank you for any comments.
Description and a Flash movie of the booster in action:
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Hissing at rest means either:
- The seal between the housing and the piston assembly has gone bad.
- The internal valve isn't seating properly, allowing outside air to constantly leak through the booster. Could be a piece of dirt, a chunk of the air filter (the pedal's pushrod goes through a foamy, spongy thing... the filter), or some kind of corrosion on the valve's seat keeping it from closing. Pressing the pedal a bit moves the internal valve enough to seal the front chamber from the rear, so no more flow.
When mine started hissing years ago, by the time I got it to the shop later that day (maybe a 20 minute drive), I had to stand on the pedal with both feet to stop, so yes, it IS a critical safety issue, unless you don't care about your life or that of others around you.
You problem can progress to a sudden catastrophic failure very quickly without further notice. It is a safety concern and should be repaired at the earliest opportunity with as little vehicle operation as possible until it is repaired. The ass you save may be mine!
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