If you have a leak in your dash then it is likely coming from the valves. Once you have the dash apart it isn't very difficult to change them out. I checked on one about a year ago and I believe they cost about $395. You may check to see if they have a rebuild kit for them. Of course, I would not replace anything until I found out where the air was leaking for sure.

 

Back when I had my own truck, I had a leak that I traced back to the parking brakes too. Sure did not cost me $395 unless someone else replaced it. I think mine was only about $170 or so. But, don't expect to get in to the air-line connections with any big wrenches. It's a bit cramped to get into a couple of them.

On the side of your air governor, there is a line that controls the "kick-out". If something has happened so that it does not get the pressure back to the governor, it will not kick out. Things like getting blocked with ice will do it. If that line is going through somewhere that it is getting "pinched off", it would do it. Take that line off the governor and the compressor won''t quit. Building up 170 psi stands to blow out lines and components that would go on for a few more years under normal conditions.

 

if it's the dash park brake it's called the mp3 valve. bought 1, 1 month ago from truck pro. 138.00 same price more or less at nearby truck parts stores.

 

I thought that was the air dryer. Or can I not hear the relief valve, because of the air dryer...

 

Last time I heard air leaking from my dash it was from a leaking brake pot.

 

Was that for the entire valves or just the rebuild kit? One of my trucks is also losing air. I am having difficulty finding the leak. I can't hear air leaking but the air drops fairly quickly when the engine is off. When the engine is running the air is where it is supposed to be. It has to be something simple. It is too difficult to find.

 

Did you check the air operated fan clutch and associated lines and control valve?

 

I haven't noticed anything from around the fan clutch. I am thinking it may be coming from somewhere under the cab since it is so difficult to hear or find. I need to get underneath the truck to see if I can find it. My other truck had a leaking air bag under the cab last year. It was very difficult to find until the leak got worse.

 

There is a plastic T to my air lines inside the dash. I had the dash apart before, I could feel the rush of air coming out of one of the lines. I also managed to find a replacement T, but I went to a number of places looking for it.

I think, in the end, all I did was jam air line harder back into the existing T and if I remember correctly, the new one I bought is laying on the floor of my storage compartment.

Yesterday I couldn't hear the leaking sound and the pressure held pretty well. You know, I don't plan to mess with it like it is.

 

Gman I have an air leak similar to yours, coming from passenger side towards the engine, but I can't find it exactly. I am thinking its the air line to the differential, since the differential don't work! But turn the truck off and poof, air goes down to 55psi in a matter of a minute, but stays there.

As far as the relief valve going off, you cannot miss it, you will hear it every now and again when it goes 'psssssffffft' One truck I drove used to sound like it was farting when the relief went off.