A few days ago I posted a message stating the brake pedal in my '94 Chevy
S10 lost tension briefly and then went back to normal.
The advice was that either a brake pad sheared off or my brake master
cylinder was failing.
Could it also have anything to do with the brake booster being connected to
engine vacuum from the intake manifold. If the engine misfired or for any
reason lost vacuum pressure, would this have affected the booster and caused
the pedal to lose tension?
What does "lost tension" mean?
If you mean that you put your foot on the pedal and it normally resists
your pressure, but this time it sank with no resistance, then that's a
hydraulic fault (and a serious "don't drive it until fixed" fault).
If you mean that the pedal is normally easy to push down (and the
brakes work) but this time it was hard to push down (but the brakes
still worked), then yes, that could easily be a problem with the vacuum
system and the brake servo (booster).
Nope. When the booster cuts out the pedal gets hard. Try it by
unplugging the booster and plugging the line to the engine.
Pedal dropping out is bad news. Make 'sure' the emergency brake works
and you know how to stop with it before driving that vehicle.
My Chevy pickup did that and I pushed it because I didn't have the money
at the time to fix it. It failed totally very soon after the first
warning.... when I was at the top of a 10 mile long hill.... Not a fun
drive down that hill to the garage at the bottom... Low range and the
e-brake kept me in control.
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
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"Nadeem" wrote: '94 Chevy S10
I posted a message stating the brake pedal lost tension
briefly then went back to normal. The advice was that
a brake pad sheared off or my master cylinder was failing.
Could have anything to do with the brake booster being
connected to engine vacuum from the intake manifold.
If the engine misfired or lost vacuum pressure would this
affect the booster and cause the pedal to lose tension?
The vacuum line from the engine to the brake booster has a
safety check valve to keep booster vacuum from disappearing
when the engine is shut off or quits. That is why you can
still use your brakes once or twice after turning off the car.
It is possible for the check valve to fail but it is very rare.
An intermittently soft brake pedal is most probably a sign
that the master cylinder is failing. Your liability depends on
how fast and in what direction you are going when it fails.
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