u might want to give a check on your water pump..

ps: i hope u never skimmed your car head before.

i'm facing the same problem as you before , send my car to workshop .. they said it caused by water pump.. my water pump fins got stuck.

change the water pump + timing belt .. then everything goes normal back.

ps: the problem might be vary , 

yeah . the ground dry. same as mine. check for a leak , got no findings. then i remembered , i never changed the water pump since i bought the car late dec 2005. till 2012.. 

Possibly hose leak between your coolant tank to the radiator. Usually assoaciated with older cars. You should be able to visuallise it if you look close

Collision before ma. U sure all parts are in good conditon after repair.

I assume coolant disappeared meaning coolant loss.  First thing you should do is flush it and then refill properly with coolant.  By properly I mean there should be no air bubbles in the system.  Clean up the spark plugs, rad cap, inlet & reservoir.  Then use the car for a day.  After that you can do your diagnosis.

Things to look for are:
- Color spread around the engine & rad coolant inlet. (hose/radiator leak, thermostat)
- Coolant level in the reservoir.  It should be over max when hot, down to max when cold. (hose/radiator leak)
- Coolant shouldn't have faint petrol/exhaust smell in it. (gasket leak)
- Exhaust smoke shouldn't be white when hot. (gasket leak)
- Fan should be running properly. (fan motor, electrical)
- Coolant shouldn't jump out like spring when start the car at cold and rev it. (gasket leak)
- Coolant should be flowing out the inlet/through steadily when car is running. (water pump, electrical)

The cheapest stuff you can replace are:
- radiator cap
- thermostat
- fan motor

my campro gen 2 2005 having this problem:
1. overheat when road jam i turn my aircond to max under hot sun .

2.loud noise from engine when i drive 80-100 above kmph

coolant in radiator missing and reservoir half full? hmmm......
Confirm thermostat working right?

Ei... your saga back? kudos... Anyway, check the rubber hose to the engine. And also the bleed nut below.

What pressure test? you mean compression test?