Brake issue
Thread Starter
Racer
Joined: Dec 2009
Posts: 382
Likes: 8
From: Wellington
Brake issue
OK, so the thing is that I have a 76 which has not had brake problems before, but the other day a strange thing started. When I use the car for the first time in the morning, the brakes do not work properly, the pedal hits the floor and there is a hissing noise coming from down by my feet. After about 30 seconds of driving it all comes right and it wont play up again until the next morning. I have had the mechanic check it out and he said that everything looks normal, the fluid is clean, the master cylinder is new(ish), the pads are good and there is no air in the system.
I am guessing that the hissing is the clue that should mean something to someone.
Any ideas?
I am guessing that the hissing is the clue that should mean something to someone.
Any ideas?
Pro
Joined: Mar 2005
Posts: 683
Likes: 4
Here's what I would think. Its the power brake booster. It's hissing in the morning probably because there is a tear in the rubber diaphram. After the motor heat up the rubber diaphram the tear will close. The same thing happened to my vacumn advance that has a diaphram in it as well.
GOOD LUCK
Steve
GOOD LUCK
Steve
Pro
Joined: Mar 2005
Posts: 683
Likes: 4
Its inside the power brake booster. The big unit that the master cylinder is attached to. I would see if the hissing is coming from this unit. It has a vacumn line attached to it. Remove the line when it is hissing and plug it with your finger and see if it stops.
Team Owner
Joined: Jul 2003
Posts: 24,650
Likes: 8
Correct me if Im wrong here..but Ive wrenched on a few cars...
The brake booster is a big diaphragm with vacuum applied to one side of it. The vacuum makes it so less foot power is required to actuate the master cylinder rod. and pressurize the lines/calipers.
A faulty diaphragm would mean there is no assist..and thus would have the effect/feel of manual brakes, meaning a hard pedal.
With or without the booster, the end result to stop is the same...the piston pushing in on the master cylinder, just one requires less work by the driver.
The brake booster is a big diaphragm with vacuum applied to one side of it. The vacuum makes it so less foot power is required to actuate the master cylinder rod. and pressurize the lines/calipers.
A faulty diaphragm would mean there is no assist..and thus would have the effect/feel of manual brakes, meaning a hard pedal.
With or without the booster, the end result to stop is the same...the piston pushing in on the master cylinder, just one requires less work by the driver.
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Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
Correct me if Im wrong here..but Ive wrenched on a few cars...
The brake booster is a big diaphragm with vacuum applied to one side of it. The vacuum makes it so less foot power is required to actuate the master cylinder rod. and pressurize the lines/calipers.
A faulty diaphragm would mean there is no assist..and thus would have the effect/feel of manual brakes, meaning a hard pedal.
With or without the booster, the end result to stop is the same...the piston pushing in on the master cylinder, just one requires less work by the driver.
The brake booster is a big diaphragm with vacuum applied to one side of it. The vacuum makes it so less foot power is required to actuate the master cylinder rod. and pressurize the lines/calipers.
A faulty diaphragm would mean there is no assist..and thus would have the effect/feel of manual brakes, meaning a hard pedal.
With or without the booster, the end result to stop is the same...the piston pushing in on the master cylinder, just one requires less work by the driver.