Checking the condition of the cooling system components should be done after the power unit has completely cooled down (not less than three hours after the engine has been stopped).
Caution! Never remove the radiator filler cap when the engine is hot!
1. Remove the radiator cap by first turning it to the left until it stops. If you hear a hissing sound, indicating excess pressure in the system, wait until it stops, then press the cap down with your palm and continue turning it to the left until it is completely released. Thoroughly rinse the cap inside and out with clean water. Also rinse the radiator filler neck. All traces of corrosion must be completely removed from the surfaces being cleaned. The coolant in the system should be relatively transparent. If the liquid is rust-colored, the system must be flushed and filled with a fresh mixture (see section Cooling system maintenance). If the fluid level does not reach the top, add a little of the required mixture to the radiator (see section Checking fluid levels).
2. Carefully inspect the upper and lower radiator hoses, as well as the smaller diameter cabin heating system hoses located between the power unit and the engine compartment bulkhead. Check the hoses along their entire length and replace defective components if cracks, swellings or signs of material aging are detected (refer to the accompanying illustration). Small cracks are usually easier to see when you squeeze the hose. Regardless of condition, hoses should be replaced approximately every two years.
3. Check that all hoses are securely fastened to their fittings/pipes. Coolant leaks usually appear as rusty or white streaks on the surfaces surrounding their source. If the hoses are secured to the fittings/pipes with twist-type clamps, it would be wise to replace them with more reliable worm or screw-type clamps.
4. Using compressed air or a soft brush, remove old leaves, insect remains and other debris from the gaps between the radiator heat exchanger plates. Try not to damage the soft heat exchanger plates or cut your fingers on their sharp edges.
5. Every other check, and at the first sign of a malfunction in the cooling system, perform a pressure test of the radiator cap. If you do not have the appropriate equipment at hand, contact a service station for assistance.
(The publication is taken from the website: ToyotaMan)