cooling system checks

Keep things cool
The smallest cooling problem can lead to a knackered engine. As over heating occurs, excess heat thins the lubricating oil while metal temperatures increase – the result will be ruined bearings and damage to pistons and cylinder bores, which can lead to high – speed engine seizure leaving the engine beyond repair. The best defence is regular servicing and constant vigilance.
How to spot problems

Cylinder head and engine block
Metal corrosion and water deposits collects in the waterways of the cylinder head and engine block, restricting coolant circulation and causing local overheating of the engines internal surfaces. This may not produce observable symptoms of overheating until the damage has been done, though pressure from local boiling may be seen as coolant loss through the overflow pipe. Serious overheating can lead to a warped cylinder head, ( ally warps fast ). If you take your head off for any reason then check it with a straight edge and feeler gauge. The face should be flat within .004-inch. But any warp is undesirable. Its best to have the head skimmed ( is possible on a 2.8 ).

Water pump.
The water pump must circulate coolant at a steady flow rate, so its drive belt tension must be set correctly to avoid slow running due to the belt slipping, or bearing damage due to over tightening.
The drive belt can split and snap, leading to rapid overheating, so it’s a good idea to carry a spare belt ( and tools to fit it ). Bearings are checked ( engine off ) by releasing the drive belt tension and rocking the pulley or attached fan sideways – any movement will be due to bearing wear.

Thermostat
If a thermostat fails open the engine will simply run cool. If it fails closed over heating will occur rapidly from cold. In the later case the thermostat can be removed ( with a cold engine ) and the vehicle driven without it fitted. This will cause no harm to the vehicle other than the engine running at a cooler temperature making it less efficient.
Over heating itself can damage the thermostat so it’s worth remembering that a faulty stat may be the RESULT of over heating rather than the cause of it. Test the thermostat by heating it suspended in a pan of water with a thermometer to see if it opens fully at the correct temperature. Alternatively check the hose temperature ( engine turned off ). When starting from cold the top hose should stay cool then heat up as the temperature gauge reaches working level and the thermostat opens. If the hose warms gradually the thermostat is probably jammed open. If the top hose stays cool after the engine has warmed up the thermostat is jammed shut. Check the temperature stamped on the thermostat to confirm the correct type is fitted. Other defects can cause same symptoms.

Hoses
Knackered hoses should renewed quickly. A weak bottom hose may collapse inwards due to suction from the water pump restricting flow. If a hose swells when the engine is hot the internal fabric will have failed. You can check simply by squeezing the hoses by hand and change any that feel too soft or show signs of surface splits /cracks. Make sure you check the bottom hose for any kind of damage as it can be damaged from off road use. TOP TIP when changing hoses a smear of washing up liquid will help you to get the new hose in place.

Radiator
Down flow rads are made with an inlet header linked by rows of finned tubes to an outlet header, the fins which conduct heat into the airflow can become detached from the tubes by vibration, corrosion or poor construction, significantly lowering the heat transfer rate.
Airflow can be reduced by mud, flies and general debris blocking the matrix. The matrix can be cleaned with a soft brush a water hose or compressed air. Be careful while doing this as the fins are easily damaged. While the rad is out it is a good idea to reverse flush it with clean water. Turn it upside down and let the hose run through it for a while until all lime scale ect has run out.

Radiator cap.
The radiator cap contains a relief valve and vacuum valve. The relief valve opens to allow excess coolant to be discharged to the overflow bottle as it heats and expands.as the coolant cools down and contracts the vacuum valve in the cap opens allowing coolant to be sucked back from the overflow bottle in to the system. The cap will also relieve any preasure that has been caused by overheating or head gaskget failure, dumping water or steam. Check that you have the right rad cap fitted for your truck. Also chech the condition of the cap. Check the rubber seal under the car is in good condition. Plastic exspansion tanks have a similar cap so make sure that is cheaked aswell to prevent preasure loss.

Viscous fan

While the engine is cool the hub of the viscous fan unit spins without putting any significant drive to the fan blades. As the engine warms and hot coolant begins to flow through the rad the airflow over the fan warms up and activates a bi-meatl coil. Movement of the coil opens a valve alowwing fluid to flow between the driving plates causing drag and the fan begins to turn with the hub.
When cooler air is detected from the rad the fluid valve closes and fluid is removed from the driven plates by centrifugal force cancelling the drive of the fan blades. On a worn viscous unit bearings can seize locking the 2 parts together resulting in overcooling and often low speed noise.

Fluahing

Annual flushing of the cooling system removes iron oxide, hard water deposits and other debris.thin hard coatings linning the inside surfaces will reduce heat transfere. This can be removed by chemical flushing. Before using flushing agents you must flush the system with frash water to remove existing suspended solids. To flush the system first remove the thermostat and top and bottom hoses. Use a hose pipe to flush in both directions from each opening alternativly until the water runs clean. Remove the rad and back flush this aswell. If it is still blocked then you may require a new rad….
After flushing especially with a flushing agent bad connections that have previously been blocked with sludge may now produce leaks, now is the time to find them. So when you have finished flushing and refilling, bring the engine up to temperature, stop the engine and check all hoses and conections for any sign of a leak.