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Old 07-26-2009, 03:07 PM   #1
LtNoogie
 
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Anyone have their brake pedal go rock hard on hot days?

I first noticed this on a hot day while autocrossing and thought it was brake fade.

I've since swapped in SS brake lines, a high performance set of rotors, and high performance pads. (this was done for the autox, not the hard brakes).
Now that summer is here, I'm getting the symptoms again. My mechanic filled the system with the ATE Super Blue brake fluid so I don't think the heat is affecting the fluid.

I'm sure that if I take the car in to the dealer, they'll blame these aftermarket parts so I'll go back to my mechanic.

Thanks in advanced.
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Old 07-26-2009, 06:06 PM   #2
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Quote:
Originally Posted by LtNoogie View Post
I first noticed this on a hot day while autocrossing and thought it was brake fade.

I've since swapped in SS brake lines, a high performance set of rotors, and high performance pads. (this was done for the autox, not the hard brakes).
Now that summer is here, I'm getting the symptoms again. My mechanic filled the system with the ATE Super Blue brake fluid so I don't think the heat is affecting the fluid.

I'm sure that if I take the car in to the dealer, they'll blame these aftermarket parts so I'll go back to my mechanic.

Thanks in advanced.

Sounds like Vapor lock, too me .
Brake fluid boiling ,
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Old 07-26-2009, 06:20 PM   #3
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The DOT 4 racing brake fluid is supposed to stop the brake fluid boiling. I'll have to check to see what could be the cause of vapor lock.
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Old 07-27-2009, 03:18 AM   #4
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Vapor lock applies to fuel lines. When fuel lines run close to the exhaust manifold or near the exhaust pipe, the gas will boil and instead of liquid gas, just vapor would feed the carb.

Long, you're not giving enough information to make a diagnosis. It could be that before you had air in the lines and now you don't.
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Old 07-27-2009, 10:50 AM   #5
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I've had that problem. I generally chalk it up to pad fade. It's not fluid fade. The pedal goes mushy when your fluid boils. What you're describing (and what I sometimes feel) is that you're giving the pedal a good firm push... the pads just aren't biting. Pad fade.

It just happens so rarely for me that I haven't bothered to change out my pads yet!
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Old 07-27-2009, 01:27 PM   #6
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^^ I agree, and its not air in the line or it would be constantly crappy.

Have you converted your fog lights to brake vents yet? :D
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Old 07-27-2009, 05:41 PM   #7
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Originally Posted by supmet View Post
^^ I agree, and its not air in the line or it would be constantly crappy.

Have you converted your fog lights to brake vents yet? :D
Or you could put on some nice , well vented Alloy's
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Old 07-27-2009, 09:56 PM   #8
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Quote:
Originally Posted by Loren View Post
I've had that problem. I generally chalk it up to pad fade. It's not fluid fade. The pedal goes mushy when your fluid boils. What you're describing (and what I sometimes feel) is that you're giving the pedal a good firm push... the pads just aren't biting. Pad fade.

It just happens so rarely for me that I haven't bothered to change out my pads yet!
I could understand pad fade if I was driving and braking hard. This was inching around the parking lot of a Walmart looking for a parking space.

I wait 10 seconds, pump the brake pedal and then it depresses and I feel the brake pads bite like normal. It's almost like something is getting under the pedal and I just can't push it hard enough to slow down.

I'm not too cool about this because it could happen at a bad time.
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Old 07-27-2009, 09:58 PM   #9
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Quote:
Originally Posted by supmet View Post
Have you converted your fog lights to brake vents yet? :D
I've got the ten feet of RV sewer hose. Just need to get down there and cut the foglight inserts.

I'm slow that way.
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Old 07-27-2009, 10:11 PM   #10
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Hmmm... that IS strange. I've only experienced it at the track and sometimes at an autocross.

Maybe you have a vacuum leak and are losing boost?
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Old 07-27-2009, 10:12 PM   #11
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Wait... you're supercharged, aren't you? Supercharged cars often have problems with vacuum... hard to have vacuum when you have boost! Look into it. You may need to add an electric vacuum pump.
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Old 07-27-2009, 10:17 PM   #12
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Ok, but the first thing I looked at was my vacuum gauge and was showing good vacuum. I'll have to find where vacuum is going to the brake system.
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Old 07-28-2009, 11:20 AM   #13
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There is a vacuum check valve on the brake booster. If that valve fails it will cause the pedal to become mighty hard. You can unscrew it from the booster and blow in either side to see if it is OK.
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