Air Brake System on Tractor/Trailer

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  #1  
Old 12-20-09, 01:59 PM
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Air Brake System on Tractor/Trailer

I have a 99 Volvo tractor trailer. Familiar with how things function on regular mechanics of trucks but question is: why would my air-brake system be over pressurizing and does anyone have any do-it-yourself (1-ideas on checking to see if your suggestion on problem is actually it) and/or (2-how to do-it-yourself fixing). Thanks!!
 
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Old 12-20-09, 02:44 PM
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How much pressure does it have? 125 to 140 is normal.
 
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Old 12-20-09, 06:07 PM
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If you're running over, say, 160, which would be too high, the problem is in the regulator. If the high pressure started suddenly or during the time you've had the tractor, the regulator could be sticking.

If you just got the tractor with the high pressure, you can set the regulator down to a lower pressure. It's usually located close to the compressor. The type depends on the engine you have, but they're not hard to figure out.
 
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Old 12-20-09, 08:06 PM
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If you have Bendix compressor the pressure regulator is on the compressor and is not adjustable. Easy to replace though and not expensive. Just make sure to pay attention where the lines are when you take it apart.
 
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Old 12-21-09, 05:37 PM
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Beer 4U2Beer 4U2 The "regulator" is normally refered to as a govenor. Bendix are the most common, they ARE adjustable, (unscrew the black plastic cap, you will see a lock nut and a threaded adjuster screw, back off the locknut and turn the adjuster screw counter clockwise to decrease pressure and vise versa). look at the picture to locate the part on your rig. If you can't open the pic just google bendix govenors and click on images. The part is cheap and I would just replace it if I were you. On a side note, there are rare occasions where the govenor is a intrical part of the air drier assembly. In that case the whole dryer will need an overhaul or replacement.
 
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Old 12-21-09, 05:45 PM
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p.s. all air brake systems that I have delt with are set to cut out at 120 psi and cut in at 90 psi. +/- a couple psi
 
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