Remove the regulator body from the manifold with a wrench.
Compressor drain valve leaking.
The valve on the outside of the pressure switch may look something like the one in the image.
By the way c clip ring shown in the picture prevents the screw from being removed from the drain valve assembly.
You can try to clean out the old one.
Product links below in order of appearance.
Drain the air tank from the drain valve.
Http amzn to 2ir0elq pittsburgh forge 12 piece screw extractor.
How to fix it.
They usually use a high strength thread locker on the drain valves so it may just be very very hard to remove.
Besides the drain valve is relatively easy and inexpensive to fix.
After cleaning replace the parts.
Makita mac700 air compressor.
To fix the air leak caused by a faulty drain valve there are three choices.
Turn off and unplug the air compressor.
Which i ve never seen done on any compressor tank.
Clean the regulator body air piston spring and cap with wd40.
Unloader valve is leaking air when the air compressor reaches the normal cut out pressure and stops but you notice while the air compressor is off that air is leaking out of a valve attached to or perhaps inside of the air compressor pressure switch.
If the check valve is now.