Cooling System Hoses — Maintenance and Repair (Mitsubishi Colt 4)

Coolant hoses are the most abused components of any car. However, careless owners are often surprised when a hose ruptures or otherwise fails. Hoses age and become stiff and cracked over time. They are exposed to high temperatures and pressures of up to 1.5 kg, cm during normal operation. Their worst enemy is oil. If it gets on the hose, it should be wiped off immediately. If the hoses are not properly secured, they will rub against surrounding components, eventually causing 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 period of fast driving. If the clamps cut too deeply into the hoses, move the clamp along the hose or replace the hose. If the hose becomes stiff or cracks begin to develop, replace it immediately.

If a hose ruptures, stop the engine as soon as possible. Carefully open the hood (there may be a stream of hot coolant under the hood). As soon as possible, throw a piece of thick cloth over the rupture. Place another piece of cloth over the radiator/expansion tank cap and twist it to relieve the pressure. This will reduce the flow and allow you to pinpoint the problem more accurately. If the problem is with one of the small hoses, it may be possible to short-circuit the rupture. If one of the larger hoses has ruptured, surgical tape or electrical tape can be used as a temporary measure. A more drastic temporary measure is to cut the hose at the rupture and insert a piece of metal tubing, securing the hose with two hose clamps. This device will hold the fluid well until 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 cause cracks in the cylinder head. If there is enough coolant in the system, you can pour cold liquid, adding it to the hot one.

Finally, if a hose bursts, you need to find out the cause before taking any action. The burst may be due to the hose being old or neglected. In this case, nothing more than replacing the hose is required. However, if it was a new hose, the cause should be found out immediately.

How to distinguish low-quality hoses

Both upper and lower radiator hoses have to work hard in adverse conditions. They are subjected to pressures of up to 1.5 kg/cm and temperatures of over 100°C, and must pass around 30,000 litres of coolant per hour - so it is important to keep an eye on their condition.

Swollen hose

A good test for a hose is to feel it for softness and porosity. Often these defects will show up as swollen spots on the hose. The most likely cause is exposure to oil. A hose can burst at any time when it is hot and under pressure.

Cracked hose

Cracked hoses appear because usually the hoses are simply inspected, but not felt to see if they are solid.

Wear of the hose end (due to weak clamping)

Loose clamps are often the cause of damage to coolant hoses. The tube-to-hose connection wears out, causing fluid to leak 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. This can be felt on the outside as a soft or thin spot.