brake problom
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Senior User
Joined: Oct 2009
Posts: 324
Likes: 1
From: VA BEACH
brake problom
well after the bracket broke and i got her back running on the 8th its down in the driveway again this time the brakes went on the way to school. brought her into the shop at school, vacuum pump tested between 18-20 psi. that and the master cylinder are pretty new. what is happening is the brakes will build up pressure after a while and you'll get one good assisted brake that will stop the truck but after that the pedal is rock hard and it wont stop the truck until it builds up enough pressure in about min or two. let me know what y'all think the problem is
Post Fiend
Joined: Feb 2009
Posts: 8,773
Likes: 1
From: Texas Coast
Could be that your brake lines are cracking inside and fouling out the calipers or cracked and a cracked strip of rubber that is acting as a check valve. You can always pull the port bleeds and gauge the lines individually. I dont know what the pressure should read but comparing the results should give you some more to troubleshoot with.
However you may have air trapped in the master cylinder or lines as well or a leaking vacuum hose or loose belt or bad bearings in the vacuum pump. These trucks are known for seizing the bearings in the vacuum pump. You can also have a faulty check valve. This condition can be diagnosed by starting the engine (to build vacuum), shutting it off, waiting four or five minutes, then trying the brakes to see if there is power assist. No assist means a new check valve is needed
Hope that helps.
Rocky
Forgot to to add this, but its for another issue
http://www.mightyautoparts.com/pdf/articles/gb0901.pdf
However you may have air trapped in the master cylinder or lines as well or a leaking vacuum hose or loose belt or bad bearings in the vacuum pump. These trucks are known for seizing the bearings in the vacuum pump. You can also have a faulty check valve. This condition can be diagnosed by starting the engine (to build vacuum), shutting it off, waiting four or five minutes, then trying the brakes to see if there is power assist. No assist means a new check valve is needed
Hope that helps.
Rocky
Forgot to to add this, but its for another issue
http://www.mightyautoparts.com/pdf/articles/gb0901.pdf
