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#28166 05/14/2003 9:25 PM | Joined: Mar 2002 Posts: 14 Member | | Member Joined: Mar 2002 Posts: 14 | After driving for about 30 minutes,my rear brakes start tightening up and eventually lock up.The pedal gets hard.Once they sit for about an hour,they will free up.I've replaced the mastercylinder,checked the wheel cylinders,replaced the rubber lines and unadjusted the brakes. The only thing left are the metal lines,which are original,but look in good shape from the outside.Has anyone had this problem ?
Thanks,
Tom | | |
#28167 05/14/2003 9:31 PM | Joined: Mar 2002 Posts: 14 Member | | Member Joined: Mar 2002 Posts: 14 | I forgot to mention that it is a 48 1/2 ton with original suspension and brakes.
Thanks,
Tom | | |
#28168 05/14/2003 10:10 PM | Joined: Jul 2000 Posts: 504 Member | | Member Joined: Jul 2000 Posts: 504 | Check the freeplay between the pedal shaft and the master cylinder.. I think you need to have more..
I don't think this relates to your problem but outside condition of brake lines is not a good indicator of what is inside.. Most times, brake lines corrode from the inside out...
Bill M
53 GMC Hydra-Matic
Home Page
http://home.comcast.net/~bd97/index.html
When you argue with a fool, two fools are arguing..
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#28169 05/14/2003 10:40 PM | Joined: Jan 2001 Posts: 198 Member | | Member Joined: Jan 2001 Posts: 198 | Yes check the rod between the master cyl. and the pedal if that does not work check the residual valve in the end of the master cyl not allowing the fluid to come back or a blocked transfer port in the master cyl. | | |
#28170 05/15/2003 4:12 AM | Joined: Oct 2001 Posts: 194 Wrench Fetcher | | Wrench Fetcher Joined: Oct 2001 Posts: 194 | Also check your brake pedal return spring. Make sure that it is returning your brake pedal to the top and not putting any pressure on the master cylinder. | | |
#28171 05/15/2003 6:06 AM | Joined: Feb 2001 Posts: 1,897 Member | | Member Joined: Feb 2001 Posts: 1,897 | Also check to see that the small port inside and on the bottom of the master cylinder is clear of obsrtuction. If it has crud covering/blocking it, it will not allow the fluid to return to the resevoir. All the things the rest of the guys said are good considerations of what the problem is. Let us know what you find 
There is enough good in the worst of us and enough bad in the best of us that it does not behoove any of us to criticize the rest of us.
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Be yourself. If you are ever lost, It will be much easier to find yourself if you know who you are!
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#28172 05/15/2003 6:30 PM | Joined: Mar 2002 Posts: 384 Shop Shark | | Shop Shark Joined: Mar 2002 Posts: 384 | I had the same thing about a year ago. I heard many things were possibilities, including the brake fluid heating up because the brake line was too close to the exhaust/heat. What seemed to fix it, however, was when I adjusted the brake linkage between the pedal and the master cylinder, so there was more room between the linkage and the floor of the truck, when the brake pedal was released. I think there was a spec in the book. - scott
55 1st Chev.
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#28173 05/16/2003 1:55 AM | Joined: Mar 2002 Posts: 14 Member | | Member Joined: Mar 2002 Posts: 14 | You guys are the ticket ! That's what it was,I had no free play. Hard to believe something that minor can cause such a major headache !Thank you all !
Tom | | |
#28174 05/16/2003 2:14 AM | Joined: Jul 2000 Posts: 504 Member | | Member Joined: Jul 2000 Posts: 504 | Nothing like a happy ending....
Bill M
53 GMC Hydra-Matic
Home Page
http://home.comcast.net/~bd97/index.html
When you argue with a fool, two fools are arguing..
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#28175 05/16/2003 6:50 PM | Joined: Mar 2002 Posts: 384 Shop Shark | | Shop Shark Joined: Mar 2002 Posts: 384 | At last...I was finally able to contribute someting for all the help I got from this board. Thanks - Scott
55 1st Chev.
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