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 Post subject: air leak
PostPosted: Wed Apr 18, 2018 2:54 pm 
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Joined: Mon Mar 30, 2009 5:16 pm
Posts: 127
I have an air leak I can't find and hope someone here can help. I have a vigorous leak from 120 to 60 in 30 minor so. once the air pressure hits 60 it will hang in for 3-4 hours. the 60# seems to be significant. any thoughts would help. My ears are no good to find it and my wife just says yep I hear it.


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 Post subject: Re: air leak
PostPosted: Wed Apr 18, 2018 7:52 pm 
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Joined: Wed Nov 05, 2014 12:49 pm
Posts: 290
Location: Horseheads NY
Sounds like your leak is cab accessory related. There is a regulator that isolates brake air from air used in the cab for wipers, air seat, diff lock etc. Best way to find it is by doing the following ---
Remove a drain valve from an air tank and install a fitting so that you can feed air to the truck from your shop compressor. This way you will have a constant supply of air without the engine running. Using a spritzer bottle spray soapy water on EVERY fitting, do the exhaust port of the treadle valve and the quick releases on the axles too. I use about a tablespoon of Dawn dish detergent to a quart size bottle. You need lots of soap so the bubble solution will hang on the fittings. Work you way from the front bumper to the mudflaps and then go in under the dash. I would suspect the old blue plastic covered fiberglass air line that runs from the manifold on the crossmember under the back of the cab up to the radiator shutter reservoir on the left front frame and then to the shutterstat. This line crumbles with age, and the air can weep out anywhere. I've seen them start leaking midway between fitting. Once all the fittings have been soaped go down all the hoses too. A couple quarts of soapy water will show the leaks. Another possible is the the air tanks themselves where the mounting bands go around the tank. Rust builds up under the band and can rot a hole in the tank. Soap this area as well.
I recently made a service call to Virginia and spent a couple hours on cute little 358 that wouldn't hold enough air to release the brakes. Using soapy water, we found the leak on the supply line feeding the trolley valve. The hose was dry rotted and the air was coming right out through the body of the hose. Hope this helps, Scott. If you need a hand, let me know and I'll stop by sometime. Stan


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 Post subject: Re: air leak
PostPosted: Thu Apr 19, 2018 5:44 am 
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Joined: Tue May 16, 2017 8:04 pm
Posts: 55
Stan knows his stuff! Spray/soap bottle is now standard shop equipment down here.


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 Post subject: Re: air leak
PostPosted: Fri Apr 20, 2018 10:44 am 
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Joined: Mon Mar 30, 2009 5:16 pm
Posts: 127
thanks Stan! I do have a quick connect on the tank to speed up the morning air up. I thought there was a secondary regulator there from what I was seeing for leaks. I'll fire up a little dawn and water and see where it bubbles. Thanks!


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