Brake pedal to floor intermittently - JeepForum.com

 
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post #1 of 7 Old 09-18-2013, 07:41 PM Thread Starter
BigAl63
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Brake pedal to floor intermittently

The last couple of days, the brake pedal has been normal on stops after start up. After a little while of stop and go driving, the pedal begins going almost to the floor. Still finally get to brakes, but the pedal is almost to the floor. Then, randomly, it returns to normal. Brakes catch at the normal position. I'm thinking master cylinder, but has anyone had this happen and what was the prob? It's full of brake fluid. 99 Laredo, 4.7 if it matters. Thanks in advance for any help.


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post #2 of 7 Old 09-18-2013, 07:54 PM
bradywgn71
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That's the sign of a bad master cylinder. Does the brake pedal get firmer if you pump the brakes?

2002 WJ Overland - 4.7HO - 231tc - 6" Clayton - 285/75-16 Cooper STT - ProComp 5129 wheels - Kevin's Offroad Belly Skid and Rock Sliders - JKS Track Bar and Disconnects - ProtoFab bumpers
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post #3 of 7 Old 09-18-2013, 07:57 PM Thread Starter
BigAl63
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No it does not. It just keeps going to the floor. Then out of the blue, it returns to normal. Pumping while I'm stopped or rolling does not help.

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post #4 of 7 Old 09-18-2013, 08:18 PM
Merc1973
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Quote:
Originally Posted by bradywgn71 View Post
that's the sign of a bad master cylinder. Does the brake pedal get firmer if you pump the brakes?
+1

2002 WJ Ltd. 4.7 V8, QuadraDrive
1973 Mercury Cougar Xr7 convertible 351CJ, C6, 9" rear
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post #5 of 7 Old 09-19-2013, 12:18 AM
silentbob21
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does seem like one of two things... bad master cylinder or some weird case of air in the lines that sometimes fixes itself hah... id go with #1

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post #6 of 7 Old 09-19-2013, 05:33 AM Thread Starter
BigAl63
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Thanks guys. I was thinking master cylinder too. Just looking for some confirmation.

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post #7 of 7 Old 09-19-2013, 09:50 AM
nickblack
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Master cylinder. Fix it quick because soon it won't come back up at all.
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