our truck has a d12 engine in it , we have a new air dryer, new governor and new air valves inside the cab, and still when the governor kicks out the psi gauge drops to about 90 before it starts pumping up again. we have no air leaks that can be heard, we are at a loss, even Lexington ky Volvo seems to be stumped, 1500.oo in and still have to problem. has anyone else had this problem? when the air compressor does kick in it pumps up to about 130+ psi, cause we thought it originally was the compressor. any ideas would greatly be apprecaited
07 volvo780 air pressure problems
Discussion in 'Volvo Forum' started by melinda824, Jan 25, 2015.
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From experience Volvo dealers are the worst at throwing parts at a problem and see what sticks, at your great expense. With what you've already done it only leaves the tanks, hoses, fittings and suspension bags. I'd be looking at hoses and fittings, get a spray bottle, 1/2 water and a squirt of soap and spray everything looking for bubbles. I've found leaks that I could not hear with this method and it's quick and easy to do. With the age of truck the rubber components are at end of life and fittings will be corroding.
*Has the compressor been replaced? Spray that too, they are known to crack around the fittings. When the compressor kicks in does it take about the same time as it always has to get up to 130psi or is it taking longer than before?Last edited: Jan 25, 2015
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Well how long does it take to drop down to 90?
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I have sprayed every hose and have replaced , a lot of little o rings, when the governor kicks out it slowly drops to 90 psi and the compressor kicks in and it goes up to 130psi then the cycle restarts. it builds back up to 130psi pretty quick but it is slower when it kicks out all the way to 90psi.
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an no the compressor has not been replaced
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First on your governor pressure range should be about 20 psi ( not from 90 to 130). You can adjust governor cut out by adjusting bolt
on the governor (under the cap).
Similar problem on my truck. Disconnect airline from governor to air compressor. Connect 120 psi air line with pressure gauge from another source to compressor unloader port (where governor airline was connected) and look if pressure drops your compressor unloader valve is bad. -
I had the same thing only with a Cummins, couldn't find anything. Turns out it was the unloader valves inside the compressor, was leaking internally and you couldn't hear it.
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