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Air pressure gauges not indicating evenly - 09pornstar - 10-15-2018
My prostar started developing another beautiful sympthom.
When i press the brake pedal only #1 gauge goes down, the other stays at 120 the whole time. When i get off the highway it slowly goes to 90 just from one pump. No audible air leaks whatsoever on tractor or trailer.
Im bringing the truck in this weekend to get the camshafts replaced but i would like to know what to expect and maybe order parts. Thanks!
RE: Air pressure gauges not indicating evenly - Nilao - 10-15-2018
When mine had this issue it was a ruptured brake chamber on the drives. The emergency side will leak anytime the knob is pressed if ttat diaphragm ruptures. If the service side ruptures it only leaks with the brake pedal pressed
RE: Air pressure gauges not indicating evenly - 09pornstar - 10-16-2018
(10-15-2018 )Nilao Wrote: When mine had this issue it was a ruptured brake chamber on the drives. The emergency side will leak anytime the knob is pressed if ttat diaphragm ruptures. If the service side ruptures it only leaks with the brake pedal pressed
I had my buddy press the brake pedal with the engine off and i checked every brake chamber and didnt hear a thing. Even when i cruise its only dropping one side. I would expect to hear at least something with that kinda pressure drop.
RE: Air pressure gauges not indicating evenly - Rawze - 10-16-2018
(10-15-2018 )09pornstar Wrote: My prostar started developing another beautiful sympthom.
When i press the brake pedal only #1 gauge goes down, the other stays at 120 the whole time. When i get off the highway it slowly goes to 90 just from one pump. No audible air leaks whatsoever on tractor or trailer.
Im bringing the truck in this weekend to get the camshafts replaced but i would like to know what to expect and maybe order parts. Thanks!
Air brake inspection...
https://youtu.be/rMZwffPGAiQ
Every person that holds a CDL license is required to do this inspection regularly to their trucks,... yet I rarely ever see anyone bothering to do so. -- If a person has just purchased that used truck, or is test driving it to see what may be wrong with it, -- TEST EVERYTHING AND THE BRAKES TOO. Do an air-brake test on it and make sure it passes. Truck-school 101 style. -- BEFORE PUTTING IT ONTO THE ROADWAYS~!!.
This is just a reminder to everyone out there -- INSPECT YOUR EQUIPMENT, MAKE SURE IT WILL PASS ALL DOT INSPECTIONS, AND KEEP YOURSELF AND THE REST OF THE MOTORING PUBLIC SAFE!> SOMEONE'S LIFE DEPENDS ON IT!>
The last thing anyone wants to face is huge fines or god forbid, someone else getting severely injured or killed because you drank coffee that day on that 15-minute pre-trip instead of actually checking your truck out or bothering to do that cdl-required air-brake inspection on regular occasion.
RE: Air pressure gauges not indicating evenly - bwake - 10-16-2018
(10-15-2018 )09pornstar Wrote: My prostar started developing another beautiful sympthom.
When i press the brake pedal only #1 gauge goes down, the other stays at 120 the whole time. When i get off the highway it slowly goes to 90 just from one pump. No audible air leaks whatsoever on tractor or trailer.
Im bringing the truck in this weekend to get the camshafts replaced but i would like to know what to expect and maybe order parts. Thanks!
When you press the pedal and the #1 gauge is the only one to drop, how hard are you getting on the brake pedal? The #1 or primary system is what controls the drive axle brakes and the steer axle is controlled by the #2 or secondary reservoir. If you are only lightly getting on the pedal, there is no reason that the steer axles are going to engage if you are loaded. (weight on drives so that's where we want the braking to happen). I would check the applied stroke with full brake application on all 6 brake positions and depending on what size chambers you are running, the stroke should be around 1 1/4 to 1 1/2". Your max stroke (again, depends on the chamber size and standard or long stroke) will be no more than 2 to 2 1/2". If for some reason any position has no stroke (possibly steer based on the complaint) you are going to have to look into the treadle valve (brake valve), the line going from it to the quick release valve under the radiator (usually) to make sure that you have psi going there. If so, check the air lines from the QR valve to each steer chamber.
One thing that many don't understand on brake stroke is this: if you have a wheel end that is out of specs on the stroke, there is an issue with the foundation brakes that needs to be addressed! Auto slacks are made to keep these things in proper adjustment and if it can't, there is a problem you need to find and fix. Do not just adjust it and hope the issue goes away, it will come back when the brakes wear again leaving you in the same position you were in to begin with.
When you say "it" goes to 90. Are we talking only one gauge, both gauges, happens every time or only in certain situations, etc? Depending on which one this is happening to can maybe tell us a little more about what is happening. The secondary system runs a lot of stuff on these trucks (fan clutch, air ride suspension (cab, chassis and seat), supplying air to the trailer tanks if the double check valve is working correctly.
There are so many things that are not going to be easy to diagnose over the web and I could write a book on what to look for depending on how the system is operating. Attached is a link to a basic air system that may help some.
http://www.totaltruckparts.net/brake/airschematics.html
RE: Air pressure gauges not indicating evenly - 09pornstar - 10-17-2018
(10-16-2018 )bwake Wrote:(10-15-2018 )09pornstar Wrote: My prostar started developing another beautiful sympthom.
When i press the brake pedal only #1 gauge goes down, the other stays at 120 the whole time. When i get off the highway it slowly goes to 90 just from one pump. No audible air leaks whatsoever on tractor or trailer.
Im bringing the truck in this weekend to get the camshafts replaced but i would like to know what to expect and maybe order parts. Thanks!
When you press the pedal and the #1 gauge is the only one to drop, how hard are you getting on the brake pedal? The #1 or primary system is what controls the drive axle brakes and the steer axle is controlled by the #2 or secondary reservoir. If you are only lightly getting on the pedal, there is no reason that the steer axles are going to engage if you are loaded. (weight on drives so that's where we want the braking to happen). I would check the applied stroke with full brake application on all 6 brake positions and depending on what size chambers you are running, the stroke should be around 1 1/4 to 1 1/2". Your max stroke (again, depends on the chamber size and standard or long stroke) will be no more than 2 to 2 1/2". If for some reason any position has no stroke (possibly steer based on the complaint) you are going to have to look into the treadle valve (brake valve), the line going from it to the quick release valve under the radiator (usually) to make sure that you have psi going there. If so, check the air lines from the QR valve to each steer chamber.
One thing that many don't understand on brake stroke is this: if you have a wheel end that is out of specs on the stroke, there is an issue with the foundation brakes that needs to be addressed! Auto slacks are made to keep these things in proper adjustment and if it can't, there is a problem you need to find and fix. Do not just adjust it and hope the issue goes away, it will come back when the brakes wear again leaving you in the same position you were in to begin with.
When you say "it" goes to 90. Are we talking only one gauge, both gauges, happens every time or only in certain situations, etc? Depending on which one this is happening to can maybe tell us a little more about what is happening. The secondary system runs a lot of stuff on these trucks (fan clutch, air ride suspension (cab, chassis and seat), supplying air to the trailer tanks if the double check valve is working correctly.
There are so many things that are not going to be easy to diagnose over the web and I could write a book on what to look for depending on how the system is operating. Attached is a link to a basic air system that may help some.
http://www.totaltruckparts.net/brake/airschematics.html
Thanks for your help and it was the brake valve that went bad! Most likely because the old air compressor was pushing oil down the line(air filter was sludgy and fan solenoid had oil on the bottom). I got new brakes all around plus new trailer so i didn't really notice decrease in stopping power. Thanks again! Now on to the next issue...i suspect coolant going into the transmission and i hope im wrong :))
RE: Air pressure gauges not indicating evenly - Chamberpains - 10-17-2018
Don't just suspect that problem. If you think there's going to even be a chance of getting coolant in with the gearbox find yourself the tool to pull the plug out and check that immediately. Coolant or even water intrusion will wipe the bearings out in no time.