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As my GT has aged, I've noticed that the brake pedal has become stiffer when the engine is off. When i go to start it, the pedal barely moves but once it starts it has normal pedal travel and the brakes work fine. I'm just wondering what would cause something like that? I've never had that happen on any of my previous cars.
FYI: It's a non-PP GT Premium with 37K on the odo. A couple of weeks ago I rotated the tires and gave the brake pads and rotors a thorough inspection (plenty of pad left and no abnormal wear on the rotors).
Last edited by TomServo92; Dec 31, 2024 at 07:47 AM.
Perhaps a vacuum leak? The brake booster uses vacuum from the engine to give you the boost. In my experience usually it'll hold the vacuum after you shut the engine off, but if you were to pump the pedal a few times with the engine off, you end up using up the residual vacuum and the pedal will get stiff.
If it's doing that right away after shutting off the car, you might have a vacuum leak. Try checking the hose going to the brake booster for cracks and to make sure it's seated properly on both the engine and the booster.
Perhaps a vacuum leak? The brake booster uses vacuum from the engine to give you the boost. In my experience usually it'll hold the vacuum after you shut the engine off, but if you were to pump the pedal a few times with the engine off, you end up using up the residual vacuum and the pedal will get stiff.
If it's doing that right away after shutting off the car, you might have a vacuum leak. Try checking the hose going to the brake booster for cracks and to make sure it's seated properly on both the engine and the booster.
I've never checked it right after turning the car off. I'll do that today and see what happens. Thanks!
Perhaps a vacuum leak? The brake booster uses vacuum from the engine to give you the boost. In my experience usually it'll hold the vacuum after you shut the engine off, but if you were to pump the pedal a few times with the engine off, you end up using up the residual vacuum and the pedal will get stiff.
If it's doing that right away after shutting off the car, you might have a vacuum leak. Try checking the hose going to the brake booster for cracks and to make sure it's seated properly on both the engine and the booster.
You were spot on! After turnng off the ignition, the pedal acts normal for a couple of pumps and then stiffens up. I'm going to inspect the vacuum hose but I'm wondering if the problem could be a faulty check valve?
I turned out to be an easy fix! When I went to pull the valve, I noticed the it didn't seem to be seated properly and was very easy to pull out of the booster. I went ahead and disconnected it from the hose and blew air through it and verified it was working. Inspected the hose and it looked good. Put it all back together and made sure the valve was firmly seated and no more brake pedal stiffness.
glad you got it figured out .... but I'm a little confused because I always expect the pedal to be harder when the engine is off, because the power brake assist does not work when the engine is off ... apparently I am missing something
glad you got it figured out .... but I'm a little confused because I always expect the pedal to be harder when the engine is off, because the power brake assist does not work when the engine is off ... apparently I am missing something
That's what was happening. It was hard when I went to start the car but went to normal after it was running. After turning it off, it would be normal for a couple of pumps and then sitiffen up again. I guess I didn't explain it well enough.
It started doing the stiff pedal thing at startup again. Given that the brakes function perfectly when the engine is running, I'm assuming that the check valve isn't functioning properly even though it passed the test when I pulled it. I ordered a new valve so we'll see if my assumption is correct.
A Brake Booster is a Vacuum Chamber. A Leaky Valve Can Cause it To Lose Vacuum or a Leak in The Booster Itself. Over Time it's Ability To Hold a Reserve Can Diminish and Eventually Come To a Point it Always Leaks and Then You Always get a Hard Pedal. The Leak Can Be a Torn Chamber or The Seal Where The Piston Goes in & Out. Sometimes When they Go Bad They Actually Suck Fluid out of Master Cylinder.
A Spray Bottle With Some Soapy Water Can Be Used To Check For Leaks At Those Areas Oh Also The Rubber Gasket The Check Valve Plugs into can Get a Split in it. Total Failure of System Can Take a Day A Week or Years Depending on What is Going South. What you Are Currently Experiencing is Worth Keeping an eye on But not Overly Concerning if it were my Car at The Current Point.
Hope My Information Helps!
BTMO
KC
I Would Also Check Sensor Grommet.
Heck Sensor itself Could Be Leaking. If Your is So Equipped!
A Brake Booster is a Vacuum Chamber. A Leaky Valve Can Cause it To Lose Vacuum or a Leak in The Booster Itself. Over Time it's Ability To Hold a Reserve Can Diminish and Eventually Come To a Point it Always Leaks and Then You Always get a Hard Pedal. The Leak Can Be a Torn Chamber or The Seal Where The Piston Goes in & Out. Sometimes When they Go Bad They Actually Suck Fluid out of Master Cylinder.
A Spray Bottle With Some Soapy Water Can Be Used To Check For Leaks At Those Areas Oh Also The Rubber Gasket The Check Valve Plugs into can Get a Split in it. Total Failure of System Can Take a Day A Week or Years Depending on What is Going South. What you Are Currently Experiencing is Worth Keeping an eye on But not Overly Concerning if it were my Car at The Current Point.
Hope My Information Helps!
BTMO
KC
I Would Also Check Sensor Grommet.
Heck Sensor itself Could Be Leaking. If Your is So Equipped!
Yeah, I thought about the booster itself might be leaking but decided it was worth $6 to change out the valve (plus it's an easy job). Also, since it got better for awhile after pulling and testing the valve, also makes me think it's the probable culprit. In a few days I'll either have my answer or ruled out one part of the system.
You Are On The Right Track, I was Just Laying Out Other Scenarios For Not Just Your Situation But Others Who Wrestle With Similar but Not Identical Pedal Issues! We are 98% Library Here and 2% Active Q&A. {EXAMPLE} 4 Active Members Logged on, 483 Viewers at the Moment. I Really appreciate it When The Op's Continue on Issues Unlike Others Who Come in Wham Bam Got My Info, No Thank You and Fail To Update What Fixed Issue. It's The Loyal Regulars Like Yourself Who Help With Good Topic Content!
