Oil is their worst enemy. If it gets on the hose, it should be wiped off immediately. If hoses are not properly secured, they will rub against surrounding components, eventually resulting in pinholes.
When checking the oil and electrolyte levels, also inspect the cooling system hoses. Check the tightness of the clamps every three months or after a long, fast ride. If the clamps cut too deep into the hoses, slide the clamp along the hose or replace the hose. If the hose becomes stiff and cracks begin to progress, replace it immediately.
If a hose break occurs, stop the engine as soon as possible. Carefully open the hood (there may be a jet of hot coolant under the hood). As soon as possible, throw a piece of thick cloth over the tear. Put another piece of cloth over the expansion tank cap and twist it to relieve pressure. The jet will then subside and it will be possible to more accurately determine the malfunction. If the problem is with one of the smaller hoses, you may be able to «short out» place of break. If one of the large hoses has ruptured, surgical tape or duct tape can be used as a temporary fix. A more drastic temporary measure would be to cut the hose at the rupture and insert a piece of metal tubing, securing the hose with two clamps. This device will hold liquid well as long as you can install a new hose.
Never pour cold water into a hot engine if it is not running: this is the surest way to crack the cylinder head. If there is enough coolant in the system, you can fill in cold liquid by adding it to the hot one.
Finally, if a hose break occurs, the cause must be determined before any action can be taken. A rupture can be caused by hose aging or neglect. In this case, nothing is required other than replacing the hose. However, if it was a new hose, the cause should be investigated immediately.
How to distinguish low-quality hoses
Both the upper and lower radiator hoses do the hard work in harsh conditions. They are subjected to pressure up to 1.5 atm. At temperatures often above 100°C, they must pass about 30,000 liters of coolant per hour - all this is the reason to monitor their condition.
Swollen hose
A good test for a hose is to feel it for softness and porosity. Often these defects show up as swollen spots on the hose. The most likely cause is oil exposure. The hose can burst at any time when heated and under pressure.
Cracked hose
Cracked hoses are usually caused by simply inspecting the hoses but not feeling for hardness. Such a hose is cracked to the cord and can crack anywhere.
Hose end wear (due to weak grip)
Loose clamps are often the cause of hose and cooling system damage. The tube-hose connection wears out and fluid flows out when the engine is hot.
Dirt in the cooling system
Dirt, rust and scale in the cooling system will cause wear on the inside of the hose. It can be felt from the outside as a soft or sophisticated place.