Wierd problem with pac brake

[Cowboy Medic]

I have a wierd problem with my pac brake. It is sticking closed, but only when the engine is cold. Once I have driven it a while and the engine gets up to temp everything works fine. Pac brake sent me a new elctric control valve and I replaced that, and that was not the problem. I have taken the brake apart and checked it all out, it does not appear that the butterfly sticks at all and the cylinder responds to the vacuum to move everything just fine. I am totally stumped on what is going on.



Any ideas?

 

[Driftwood Ram]

I have a wierd problem with my pac brake. It is sticking closed, but only when the engine is cold. Once I have driven it a while and the engine gets up to temp everything works fine. Pac brake sent me a new elctric control valve and I replaced that, and that was not the problem. I have taken the brake apart and checked it all out, it does not appear that the butterfly sticks at all and the cylinder responds to the vacuum to move everything just fine. I am totally stumped on what is going on.



Any ideas?

Have you ever lubed it??I had to replace the vacuum cylinder on mine. Before you do that pop the hood and see if you can move the butterfly by hand, engine running when it is stuck closed. Proceed with caution. You might try disconnecting the lever and make sure the butterfly dies not bind closed, engine not running.

 

[Cowboy Medic]

Yep I usually lube it once in the spring and once in the fall. I can open and close the brake by hand and it does not feel like it sticks at all. The times when it sticks I can get out and manually push it closed. To me it is almost like air pressure is getting stuck instead of being vented. But like I say, Pac Brake sent me a brand new control valve and it hasn't made a difference. I guess what makes it seem the most wierd to me is like I say it only does it when it is cold, once it has warmed up it works fine. About the only thing I can still think to try is to see if I can pull the vacuum cylinder apart and see if it is dirty inside of there, but I am not sure if it can be disassembled and reassembled or if it is an item that just has to be replaced.

 

[NIsaacs]

Cowboy, check all your vacume lines while truck is cold. Sometimes they will leak when cold, then seal up when warm. It sounds like low vacume to me. Use a guage if you have one, with the noise of the motor, it can be dang hard to find a vacume leak.





"NICK"

 

[WDaniels]

Hey Cowboy,

take off the solonoid and clean it. They get carboned up and stick. Mine is doing it right now. You can check it by reversing the two larger lines that come into the solonoid. When you start it up the valve will close. Then rev it up, the brake should stay closed. Now put them back. If the brake opens, it sounds like the solonoid needs cleaned.

WD

 

[Cowboy Medic]

WDaniels, I just put a brand new solenoid on. So it should be clean. I am thinking maybe NIsaacs may have it as the brake has been on the truck since about a week after it came home and the lines have been taken off and put back on, but never replaced so they could be wearing enough to be giving me a small leak. I am going to try replacing the lines tomorrow. They are cheap and are probably due anyway.

 

[Driftwood Ram]

I do not think the canister is field repairable. Like perviously suggested you can put a vacuum gauge on at the canister. Hope just replacing the lines works. If not, the canister seals still could be leaking. If you take it off you can just stick your thumb across the holes one at a time and see it you can move the rod. With the hole blocked, you should not be able too.

 

[Cowboy Medic]

That sounds easy enough to check. Thanks!!!