Why the oil will come out from the sander? how many oil drop must regulate the regulator

If an automatic oiler system is not used, add a few drops of Pneumatic Tool Oil to the airline connection before operation.
Add a few more drops after each hour of continual use.
buy oil at HF where you bought sander, or HD, lowes.

https://www.manualowl.com/m/Harbor%20Freight%20Tools/280/Manual/429462?page=1#manual

call deon sanders

check oil level in sump. You may have to remove the sump to check for cracked oil pick up line . Check oil pump pressure regulator . replace oil filter as it may be blocked and dropping the oil straight back to the sump.

it seems like you might be adjusting a valve before the regulator. the outlet pressure from the compressor vessel should remain celatively constant. if you are adjusting the pressure whilst using the airtool and when you stop the regulator gauges return to/or close to/ the 150 PSI then this also points to you not adjusting the regulator.
Some compressors have 2 outlets... one regulated and the other not.

Over time water and debris will enter the regulator and cause problems. Easy to fix however. Drain air from tank and turn pressure control knob out to relieve pressure on the internal spring. Open the regulator and clean and lube the internal parts (use silicone paste lube on rubber parts). Some regulators have a small nut on the rear that should be remove to clean small piston. If parts are rusted beyond usefulness, replace with generic regulator that will fit into space. Good luck

Are you sure pressure is dropping or is it a bad sending unit? the pressure is regulated by the oil pump and heat should not effect. Check the sending unit for proper operation

REMOVAL

1. Remove front cover.
2. Remove oil filter adapter, pressure regulator valve and spring.

Fig. 16 Oil Pump & Housing

1. Remove oil pump cover attaching screws, then the cover and gears, Fig. 16 .

INSPECTION

1. Check pump cover and housing for cracks, scoring, porous or damaged casting, damaged threads or excessive wear or galling. Replace as required.
2. Check pressure regulator valve for scoring, burrs or sticking in valve bore. Replace as required.
3. Check pressure regulator valve spring for tension loss or bending, replace spring as required.
4. Check gears for chipping galling or excessive wear, replace as required.

Fig. 17 Oil Pump Inner Gear Tip Clearance Inspection

1. Measure oil pump inner gear tip clearance, Fig. 17 . Maximum clearance should be 0.006 inch.

Fig. 18 Oil Pump Outer Gear Diameter Clearance Inspection

1. Measure oil pump outer gear diameter clearance, Fig. 18 . Clearance should be 0.008-0.015 inch.

Fig. 19 Oil Pump Gear End Clearance Inspection

1. Measure oil pump gear end clearance with gear dropped in housing, FIG 19. Clearance should be 0.0010-0.0035 inch.
2. Measure pressure regulator valve for valve to bore clearance of 0.0015-0.003 inch.

INSTALLATION

1. Lubricate all gears with clean motor oil, then install gears in housing.
2. Pack pump cavity with suitable petroleum jelly.
3. Install pump cover and cover attaching screws. Tighten cover attaching screws to specifications.
4. Install pressure regulator valve and spring.
5. Install oil filter adapter using a new gasket, tighten oil filter adapter attaching bolts to specifications.
6. Install front cover on engine. During front cover installation, ensure inner pump gear is properly engaged on crankshaft sprocket.

Many belt sanders have sealed bearings that are packed with grease at the factory. They require no further lubrication. Sleeve bearings should be lubricated with 30 weight oil or an equivalent after each 10 hours of use.

Only about 2 to 3 drops of oil should be applied to each sleeve bearing. Avoid using too much oil. It can get on the work piece or on the belt and the belt will slip.

what oil regulators?? only change the oil filter and oil ,their is no regulator only a pressure relief valve but thats in the oil pump ,if the injector failed ,and allowed neat fuel into the piston then this would cause the piston to seize because it wash all the oil off the cylinder bore .then seize up time

It sounds like you have trouble with your pressure regulator. Make sure that the knob for the regulator is turned clockwise to increase pressure. If this doesn't work, you may need to replace the regulator.