Hello All, I have read through the other brake problem threads with no luck. I have a 1974 Case 680. Some days the brake air pressure will build up to 120+ and I will occasionally hear a release valve letting off air (sounds like it is coming from near the tank, I assume this is the safety valve on the tank). Other days it will not build up past 60 and I cannot release the parking brake. Any ideas what the issue is? Pressure regulator, parking brake valve? Thanks much in advance.
First i would drain the air tank to see how much oil/water is in it, there is a auto bleed on some that i have seen but would still check. I think your issue may be with the air governor, the gov controls the compression of air, it starts or stops compression when it reaches min/max amount of air pressure. When the system reaches max pressure the gov sends air to the unloader valve in the compressor that stops pumping air to the air reservoir. The sound you hear is the gov not sending the air to the unloader popping off the pressure relief at the air tank. Not much to fix on the gov, most times replace them. unloader in compressor may need a reman unit. You can also run your shop air into the tank with you regulator set at 115psi and check for air leaks/brake functions/parking brake/ always block your wheels so it won't roll.
Mattyweb, I also have a 1974 680CK. They are an absolute nightmare when the air is not staying up at 125 to 150 psi. I found the best way to find leaks is to remove the air line on the discharge side of the air compressor and hook a shop compressor onto that line. By doing that you will be able to hear the hissing because there is no engine noise. You may have one or both brake chambers leaking. I would check them first. Set the parking brake. You will know immediately if they are leaking. The hissing and pop noise is most likely the air brakes setting because of low air pressure. That noise comes from the parking brake valve in the dash. Put some soapy water in a spray bottle and start checking all the connections. You will have to lay on the floorboard to check the hose fittings on the parking brake valve and the air pressure gauge in the dash. You can make new air lines by using D.O.T. 1/4 air line that is available at any auto parts store. NAPA near me had the line and the fittings I needed. Don't forget to put the little brass sleeve in the ends before attaching and tightening the nuts. Be sure the hydraulic tank filler cap is not leaking air because the tank is charged with a constant 15 psi. There is a moisture ejector on the bottom of your air tank and also a safety valve on the left side,center.
Thank you both for the help, much appreciated. Tomorow i'll start by seeing if i can charge the system with my shop compressor and see if there are any leaks. I was wondering if it was the governor too. My repair manual says there is a rebuild kit for it, if i can find one. Thanks again, for the suggestions. I'll post up again when i know more.
Hi, Just wanted to post up results and say thanks. I added shop air to the hose from the outlet off the governor and no leaks, everything worked as it should. So I took the governor off and rebuilt it. Wow was it dirty, full of crusty debris that looked like the inside of an old radiator. Cleaned it all out, re-greased it, and re-assembled it and viola!, works like a champ. Pressure built up to 130 right away. For anyone attempting this, an easy way I found to remove the piston in the governor was to remove the top end until the piston is exposed, then apply air to the outlet and it will pop right out. I had to clean the cylinder above the piston first as it was fairly corroded. I love how these machines were so well engineered. I didn't even need to buy any parts, just service it. Can't do that with anything built these days. Thanks again for the help!
Thanks for posting back what you found. Finding that there were no air lines leaking is amazing !
I was surprised to find no leaks as well, although in honesty I have to admit it is only half-amazing. The guy who had the machine before me disconnected the left brake stating the diaphragm leaked. Works good if I need to make right turns though That is a project I have yet to tackle and I'm not even sure where he disconnected it. From underneath all the lines are still connected to the chamber and none are capped. I suspect he did it at the pedal. Have you repaired one of the one of the actuators before? I am aware there is a large spring and will not attempt this at home, but wondering what the best method is. Bring the whole can to a brake shop and have the diapragm replaced or replace the whole can itself? I heard there is a non Case equivalent actuator available at Napa for 1/10th the price but I do not know the part number equivalent.
The actuators are easily repaired . Usually they only need cleaning and a new bladder. It must be done by a professional with the proper tools and training. Just remove the can assembly and let them do the rest. Most any truck and trailer shop will have the parts and be able to fix it. When mine were done I don't recall what it cost but it was not very expensive.