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Slow Brake Release

Posted By beemergary Sunday, June 26, 2011 5:10 PM
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beemergary
 Posted Sunday, June 26, 2011 5:10 PM
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Got my first big truck 359 Pete  It takes a good 5 seconds for the brakes too release. The fronts release right away but the backs don't. All four back brakes move freely so I am thinking its in the air system. If you just barely touch the pedal they will work faster. HELP THANKS
peterj
 Posted Monday, June 27, 2011 12:07 AM
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It's likely the relay/quick relase valve.  It could be just bees/wasps building in the exhaust port...  or dirt , rust inside...

peterj 

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White9064TD
 Posted Monday, June 27, 2011 1:02 AM
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I agree with the quick release valve just go to NAPA and swap it out.  Do you have a copy of Bendix Airbrake Handbook, I think they have it in the Research library.

Dan:cool:
Monday, June 27, 2011 1:03 AM by White9064TD
JeffLipinski
 Posted Monday, June 27, 2011 3:46 AM
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Make sure the plunger in the foot pedal isn't just dragging (weak spring or steel piston corroded in aluminum housing). First bet is mud wasps in the quick release. Has the truck been sitting for any length of time? 

Jeff
beemergary
 Posted Monday, June 27, 2011 5:11 AM
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Truck was setting for a good 12 years. Is the quick releasevalve the one that has like 5 lines going too it. I did take that apart. Says Bendix on it and there's a piston with a O ring on it and a spring. Looked good but cleaned it and lubed the O ring. Didn't make a difference. There's also a smaller looking valve by it with 3 lines and one goes to the Bendix valve - one to the junction block too the front axle brakes and the other towards the front of truck.
JeffLipinski
 Posted Monday, June 27, 2011 10:15 AM
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Five lines is probably the relay valve. Is this  valve back by the axles on the frame? A quick release is usually mounted on the axle or very close to it- three lines, one in, two out to the brake cans. You could mistake it for an oversize T if you weren't paying attention. If you follow the lines off the cans up, the quick release is the first thing you (should) come to. 

Jeff
beemergary
 Posted Tuesday, June 28, 2011 3:39 AM
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The big valve is mounted on the frame. Did a search on what a quick release valve looks like. Thats whats on the front brakes and also on the parking brakes. Abig burst of air comes out when you release the pedal and they work fine. The service brakes are the ones being slow and the air comes out of the relay slowly. Does that relay suppose to work as a quick release even though its called a relay?
jungerfrosch
 Posted Tuesday, June 28, 2011 4:25 AM
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The relay acts as both a relay and as a quick release valve.   There is a high pressure line to it from you tank, lines out to your brake chambers and a control line that will run to your foot pedal.  Without a relay valve you can have a delay in rear brake engagement as the air must travel though the lines to the rear.

Most likely your relay valve is not venting properly.  I'm not sure if they are serviceable or not.

Tad





46 Chevy OS 1.5 ton, 47, 48 & 49 IH KBS-8-1, 51 IH L195 Wrecker, 60 IH RF195, 64 F250 16ft flatbed, 65 Datsun 320, 72 IH Travelall
beemergary
 Posted Tuesday, June 28, 2011 2:39 PM
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jungerfrosch (6/28/2011)
The relay acts as both a relay and as a quick release valve.   There is a high pressure line to it from you tank, lines out to your brake chambers and a control line that will run to your foot pedal.  Without a relay valve you can have a delay in rear brake engagement as the air must travel though the lines to the rear.

Most likely your relay valve is not venting properly.  I'm not sure if they are serviceable or not.

Tad
OK So I see a triangle shaped metal plate. Its pretty rusty but there's a hole drilled into the valve with another hole thats full of rust probable from the metal cover. I clean it out andNOW THE BRAKES ARE WORKING FINE------THANKS 
jungerfrosch
 Posted Tuesday, June 28, 2011 3:23 PM
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That's great to hear.

Tad





46 Chevy OS 1.5 ton, 47, 48 & 49 IH KBS-8-1, 51 IH L195 Wrecker, 60 IH RF195, 64 F250 16ft flatbed, 65 Datsun 320, 72 IH Travelall

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