Originally Posted by porourke
Check valves block flow in one direction and allow it in the opposite direction. Most are a Ball,spring and cone setup in a tubular sleeve container threaded on both ends. Before I found the leveling valves leaking on my coach this is one of the things we checked. My pump sets just inside the front service compartment area and to the right of the radiator, below it is the 2 or 3 gallon accumulator tank, Commming off the pump is the pressure out line that goes to a Tee fitting. One line going to the Tee comes off of a 12v
normally open solenoid that comes on and off with power to the compressor. The other line goes to the check valve. The other side of the check valve goes to the bottom of the accumulator container just below the pump..The reason for the Soleonid is to keep the pump from comming on with Hi pressure on its output and deadheading it.. When the pump comes on and the solenoid comes in it closes the exhaust off the check valve stays closed till the pressure in the lines between the check valve, pump and solenoid gets high enough to over come the spring in the check valve and it opens up sending air to the accumilator. With the system fully aired up, 140# on the dash air guage, we took the line on the side of the check valve loose on the side going to the pump and soleonid, put a short pice of Tygon clear flexable tubing on the end of the check valve and taped it to some of the wireing comming off the pump with the tubing opening pointing streight up. Next filled the clear tube with 3 in 1 oil and waited for bubles to show up and rise in the oil but after an hour decided there was no leakage at that point.
The next used vehicle I buy, I hope it is from a gentleman who does the research and repair like "POROURKE".
It takes time and love of what you are doing to do the RIGHT repair.
It is not difficult, but you have to start the job, determine exactly what the problem is, and with the repair completed, there is the satisfaction that another good job has been well done.
Ownership is only part of the fun. Great satisfaction is gained from exploring every aspect of your unit including repair.
A lot of information on this site and others will generally led you in the right direction.
Always document your repairs so that future investigation will be easier.