Air system leaks! I want a cure

[cessnatwin]

My M818 Looses air over several hours, and I have replaced the inside cab hoses and sprayed the lines with soapy water, but it stall looses air somewhere fast. Does anyone have any suggestions to solve this. Also, once in a while some sort of valve that I can barely reach from the passenger side behind the fuel tank on what appears to be the transfer case leaks and I can just reach it and hear it, seems to be a valve of some sort, it poors it out quick, but not all the time! any ideas on what this is or how to fix it?

 

[Westech]

the valve for the t case is for your 6x6. if it hissing, time for some new seals. Its not hard to do I hear. I too need to rebuild that valve.

 

[rosco]

I'm not familiar with the 818 specifically, but on air systems, you have a number of different valves that are supposed to do something for you. Leaking is not one of them. These trucks that have the copper air lines, often have corrosion inside of them. Some of the valves are "quick release valves", and "relay valves". When they are activated, they charge something else with air, and when they are de-activated, they exhaust the charge. If the valve is sticky (old age & contaminates), they don't re-seal, after the exhaust cycle. Something holds it open. Sometimes here in the North, that happens in winter when moisture gets into the air system, and ice crystals keep the valve from sealing...... So you loose/dump your air, or can't build any, or enough.

The notion that air valves should be accesible is idealistic. Sometimes I have used a spray can of silicone lubricant with the fine little straw to put the lube in a line, upstream of the valve. The air system will disperse the lube, hopefully with positive results.

The best advice is to study the tech sheets and learn the air system, so that you can trouble shoot it at the red light intersection, because the truck dumped the air, when you touched the brakes, and you can't move it.

Westfolk is right, with the brakes applied, and 5psi/minute with a trailer, brakes applied.

Lee in Alaska

 

[m16ty]

That's not a bad time for losing air.

All air systems leak. Some more than others. My rule is if I can hear the leak I'll try and find it and fix it.

 

[5_TON_TOMATOE]

All air systems leak. Some more than others. My rule is if I can hear the leak I'll try and find it and fix it.

 

[70deuce]

On all my trucks, deuces and 5 tons, air slowly leaks past the emergency air line valves mounted on the frame at the rear of the truck, probably on the front valve on the 5 ton. Can tell this because when I take the gladhand cover off, it spews a little air for a second. Can't hear air escaping so I don't think this would be a 2 hour leak but it is another source of leakdown.

 

[70deuce]

One more place, also found a small leak on the 818's low pressure switch.

 

[cranetruck]

On all my trucks, deuces and 5 tons, air slowly leaks past the emergency air line valves mounted on the frame at the rear of the truck, probably on the front valve on the 5 ton. Can tell this because when I take the gladhand cover off, it spews a little air for a second. Can't hear air escaping so I don't think this would be a 2 hour leak but it is another source of leakdown.

If it's the glad hand at the top left in the dwg below, it should have a vent, a build-up of pressure in this line from leaking check valves will begin to apply your brakes....