My pressure relief valve on the air tanks has started to pop open every 10 seconds or so. My gauge shows 100 psi and doesn't drop for the second or two the valve is open. The needle is to the right of the 90 line about an 1/8" of an inch. Is that pegged for the gauge where I might actually be at a higher pressure? The valve looks original to the truck, 1970. Do the springs get weak with age? It looks like there is adjustment on this, should I mess with it or just replace it? Is there any place I can screw in a gauge to check pressure vs the reading on the dash? It's LOUD when it opens. I think I've startled a few drivers sitting to my left at lights.
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Pressure Relief Valve Opening
- Thread starter renovate7
- Start date
kaiser2help
Member
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- East Freetown, MA
I have had the same problems with mine. This is known as the air governor. Before you dare to take the undaunting challenge of touching the adjustment, and it is adjustable, try checking the sending air line from the top of the air compressor that travels to the air governor and check that there is no cracks or hole, as well as loose fittings,in the line. This will cause inconsistency in the governors ability to stop the comp at the factory set pressure. My truck had a rigid line between the two and there was no coil placed in the line so therefore the compressor is mounted to the engine and the gov to the firewall. There is allot of flex between the two. So if you install a rigid line be sure to coil the line in 2 or 3 coils at the fire wall to allow for flex. Hope this helped.
acetomatoco
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I believe he means the safety blowoff valve on the air tank. Should not open til 120 or more psi. Just put in a new one....
Jake0147
Member
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- 18
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- Panton, VT
If you want to verify the pressure, The drain cocks on the bottom of the air tank are 1/4 pipe thread. Many standard gauges fit there with no adapters needed. Turned right, it's viewable without crawling under. There are many other places, that is just the easiest/least wrenching that come to mind.
Ace is probalby right though, time and the elements and contamination can "uncalibrate" the blowoff valve pretty easily.
Ace is probalby right though, time and the elements and contamination can "uncalibrate" the blowoff valve pretty easily.
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- Interlachen Fl.
You could put test gage on aux.air line under glove box on firewall if you wanted to check that the gage and governor are correct. The tank drain could be removed to take reading also. Not saying anything wrong but this rules out two things with just hooking up gage. The TM's if found call for 105 psi.
Thanks for the help. I got a 0-200 gauge at Lowes and put it in the air tank. The bed is at the sandblaster so everything is easy to get to...I found I'm building to 140 psi then the valve opens and it bleeds down to 120 before closing. Definately not good. When I first got this in February it wouldn't build pressure above 30, on the dash, so I've suspected a bad regulator. After a few starts it has been OK untill this. I adjusted the screw on the regulator so now it builds to 110 then the regulator on the firewall opens and it bleeds down to 80 before building to 110 and opening again. I've also learned that the dash gauge is either broken or pegged just to the right of 90 line. I already have new gauges that will be installed when I do the dash. I'm going to Aberdeen so a regulator has been added to "the list".