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Blue brake valve

Posted By Dan Jacobs Thursday, March 26, 2009 2:06 PM
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Dan Jacobs
 Posted Thursday, March 26, 2009 2:06 PM
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My 79 W900 has three brake valves a red one, A yellow one, and a blue one. Obviously the red and yellow one are for the tractor and trailer parking brakes. What's the blue one for? It doesn't seem to make a difference wether it's in or out. Pardon my ignorance on this.

Dan Jacobs 

Dan Jacobs

79 W900A

DENNY
 Posted Thursday, March 26, 2009 3:52 PM
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blue should be tractor parking.yellow is both tractor and trailer parking,and red is trailer supply.if your bobtail and trailer supply cut off you can set tractor brakes with blue or yellow.hope this helps.
John Costley
 Posted Thursday, March 26, 2009 8:05 PM
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Dan,

Im no brake expert, but if I remember right, there was a change in the regs that required the trailer parking brake controller to set ( pop out ) when the tractor parking brakes were set ( pulled out ).Most older tractors with the three line system got updated and the blue valve got bypassed when the updated tractor protection valve and tractor parking brake controller were installed.Most guys just left the blue valve in the dash to fill the hole.You still find some tractors that never got updated.Read this  http://www.bendixvrc.com/itemDisplay.asp?documentID=5393  Theres alot of good info here,  http://www.bendix.com/en-us/service/library/Pages/Home.aspx  Everyone should download a copy of the air brake handbook and read it.Pretty handy.John

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Thursday, March 26, 2009 8:07 PM by John Costley
MIKE WALLACE
 Posted Friday, March 27, 2009 3:56 AM
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I've seen blue green or black to release the parking brakes air reserve valve.

 Mack? I ain't no Mack! I'm a Peterbilt for dang sake! Turn on your lights, ya moron! ...
bobbym
 Posted Friday, March 27, 2009 4:15 AM
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I had a 1970 kw ,if I remember right it was for an emergency brake release to get to the side of the road ,or move the truck if it was out of air.it seems to me you push it in and hold it.if it is working right you have a short supply of air.
Scott Waggoner
 Posted Friday, March 27, 2009 4:50 AM
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KW's had a small air tank with a check valve that was just for getting you off the side of the road. It usually had a green knob and was located to the far right of the air control valves. Blue was tractor only as stated before. We used the blue tractor only alot with our log trucks as you were "trailerless" half the time. When they changed the DOT regs. like John stated they would check and make sure they ,red,yellow popped out when are was low or pulled yellow. They didn't hassle us on making us change that system, at least around here!

Scott Waggoner
Mike Garrett
 Posted Friday, March 27, 2009 7:55 PM
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1995 Kenworth I drive here in NewZealand [Aussie built] has a black button on dash for truck park only, really useful on a log truck for filling air bags on trailers and getting air up with bolsters[bunks] that are moved by air rams [most of our log trucks are truck and pull trailer or B trains] but all the newer stuff just has only the red and yellow buttons and no trailer supply with truck park applied.
Rob
 Posted Friday, March 27, 2009 8:12 PM
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Seems the slide axle trailer, (Landoll type) guys would like to be able to lock the tractor brakes solid to allow the trailer to be operated on an incline.

Rob

Rob
 Posted Friday, March 27, 2009 8:15 PM
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John Costley (3/27/2009)
Dan,

Im no brake expert, but if I remember right, there was a change in the regs that required the trailer parking brake controller to set ( pop out ) when the tractor parking brakes were set ( pulled out ).Most older tractors with the three line system got updated and the blue valve got bypassed when the updated tractor protection valve and tractor parking brake controller were installed.Most guys just left the blue valve in the dash to fill the hole.You still find some tractors that never got updated.Read this  http://www.bendixvrc.com/itemDisplay.asp?documentID=5393  Theres alot of good info here,  http://www.bendix.com/en-us/service/library/Pages/Home.aspx  Everyone should download a copy of the air brake handbook and read it.Pretty handy.John

My 73 RL has a TP-3 valve and the blue knob in the dash cannot be pushed in as it has air pressure on both sides of the piston. You can push it in but there is no detent and it is like squeezing a rubber ball. It comes out as you release pressure.

I wonder if this is because of the "update" to a TP-3 as there is a PP7 in the dash for the trailer brakes?

Rob

John Costley
 Posted Friday, March 27, 2009 10:58 PM
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Rob (3/28/2009)
John Costley (3/27/2009)
Dan,

Im no brake expert, but if I remember right, there was a change in the regs that required the trailer parking brake controller to set ( pop out ) when the tractor parking brakes were set ( pulled out ).Most older tractors with the three line system got updated and the blue valve got bypassed when the updated tractor protection valve and tractor parking brake controller were installed.Most guys just left the blue valve in the dash to fill the hole.You still find some tractors that never got updated.Read this  http://www.bendixvrc.com/itemDisplay.asp?documentID=5393  Theres alot of good info here,  http://www.bendix.com/en-us/service/library/Pages/Home.aspx  Everyone should download a copy of the air brake handbook and read it.Pretty handy.John

My 73 RL has a TP-3 valve and the blue knob in the dash cannot be pushed in as it has air pressure on both sides of the piston. You can push it in but there is no detent and it is like squeezing a rubber ball. It comes out as you release pressure.

I wonder if this is because of the "update" to a TP-3 as there is a PP7 in the dash for the trailer brakes?

Rob

Rob,

Sounds like it, but I had thought the blue would be dead and bypassed after the changeover.Sounds like youres is " looped ".Hey Glenn, want to chime in on this?,lol.

Theres an amazing wealth of info in the Bendix literature library. Tech updates, Service bulletins, disconiuations, plumbing diagrams, past and present catalog pages with part numbers.I found valves in there for functions I didnt even know were possible, amazing what you can do with air.Takes awhile to read thru it, but very educational.Not just for brake valves, lots of other info there too.John

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Sabattus,Maine

Friday, March 27, 2009 11:03 PM by John Costley

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