CONJIN
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Can I replace this plastic 2way check valve found behind the front bumper with one of the Haldex type 2way check valves found under the left side cab? 
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2way check valve
- Thread starter CONJIN
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Ronmar
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Thats a weird looking 2way. Where exactly was it located? Whats on the bottom side? On an LMTV the closest(and only) 2ways to the bumper are located in behind the drivers step up under the drivers floor. 3 in a row, to interface the front glad-hands to the park, primary and secondary brake circuits.
that actually looks kinda like a 2 port quick release valve. They use one for the front brakes and it is in behind the bumper over the front axle. If it is, there will be a rubber flapper on the underside that we can’t see in the pic you shared.
that actually looks kinda like a 2 port quick release valve. They use one for the front brakes and it is in behind the bumper over the front axle. If it is, there will be a rubber flapper on the underside that we can’t see in the pic you shared.
CONJIN
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Well that sounds like what it is, so I guess it's supposed to vent out the bottom?
The problem I have is when I drive up my driveway and then roll back down in neutral the front service brakes (and possibly the rear, but I've only checked the front) lock up. I verified this by jacking up one front wheel. After about 10 minutes you can hear air vent from somewhere and they release. But as soon as I drive and use the brake a couple times, they lock up again.
Ronmar
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Yes it vents out the bottom. It is a remote pressure regulator it matches the outlet port pressures to the input pressure by either passing input to output, or venting output out that bottom vent.
Your problem sounds like your front gladhands are capped? They must be vented. 2ways take in air from either input and pass it to an output. In this case air in from the treadle/pedal valve or the front service gladhand when being towed and out to the brake system. 2ways can leak past and if the gladhand is capped, that chunk of line will build air like a storage tank while you are stepping on the pedal. When you let off the pedal, the 2way shifts and applies air stored in that line to keep the brakes applied untill the air leaks away and releases the brakes.
fronts must be vented, rear gladhands must be capped…
under the drivers floor are three 2way valves. The top with a pressure sw is for the park system. The bottom 2 that are connected together on one side are for the service brakes. One or both of them are leaking. The side that is connected together connects to the front service gladhand. Yes it was applying both front and rear brakes.
if the red gladhand is capped and its 2way leaks, you cannot apply the park brakes as the trapped air will keep the park springs compressed untill it leaks away.
the service 2ways are real easy to bypass until you get a replacement 2way. I did a youtube video on their removal, but bypassing them only takes a few minutes and no permanent modifications. you need to see how bad the front gladhands vent when you step on the brakes to see how bad the 2way is. They can also be disassembled and cleaned…
Your problem sounds like your front gladhands are capped? They must be vented. 2ways take in air from either input and pass it to an output. In this case air in from the treadle/pedal valve or the front service gladhand when being towed and out to the brake system. 2ways can leak past and if the gladhand is capped, that chunk of line will build air like a storage tank while you are stepping on the pedal. When you let off the pedal, the 2way shifts and applies air stored in that line to keep the brakes applied untill the air leaks away and releases the brakes.
fronts must be vented, rear gladhands must be capped…
under the drivers floor are three 2way valves. The top with a pressure sw is for the park system. The bottom 2 that are connected together on one side are for the service brakes. One or both of them are leaking. The side that is connected together connects to the front service gladhand. Yes it was applying both front and rear brakes.
if the red gladhand is capped and its 2way leaks, you cannot apply the park brakes as the trapped air will keep the park springs compressed untill it leaks away.
the service 2ways are real easy to bypass until you get a replacement 2way. I did a youtube video on their removal, but bypassing them only takes a few minutes and no permanent modifications. you need to see how bad the front gladhands vent when you step on the brakes to see how bad the 2way is. They can also be disassembled and cleaned…
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CONJIN
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No, the gladhands aren't capped but I did find the cover for the service gladhand had the vent plugged up!View attachment 885225
No the gladhands aren't capped and I've already cleaned the shuttle valves in the 2way check valves under the left cab. But I did find the service gladhand cover had the vent hole plugged up! Problem solved, brakes are working normal again! Thanks! View attachment 885226
CONJIN
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Ronmar
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That will do it
CONJIN
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Thanks for your help, I do appreciate it!That will do it