Warning: The engine must be cool before beginning this procedure.
1. Check the coolant level (see Daily (pre-ride) checks).
2. On XL600V and XRV750 models remove the fairing side panels, and on XL650V models remove the fairing (see Chapter 8). On all models remove the belly pan see Chapter 8).
3. Check the entire cooling system for evidence of leakage. Examine each rubber coolant hose along its entire length. Look for cracks, abrasions and other damage. Squeeze each hose at various points to see whether they are dried out or hard. They should feel firm, yet pliable, and return to their original shape when released. If necessary, replace them with new ones (see Chapter 3).
4. Check for evidence of leaks at each cooling system joint and around the pump on the lefthand side of the engine. Tighten the hose clips carefully to prevent future leaks. If the pump cover is leaking, check that the cover bolts are tight. If they are, replace the O-ring in the cover with a new one (see Chapter 3).
5. To prevent leakage of coolant from the cooling system to the lubrication system and vice versa, two seals are fitted on the pump shaft. On the bottom of the pump housing there is a drain hole (see illustration). If either seal fails, the drain allows the coolant or oil to escape and prevents them mixing. If both seals fall the oil and coolant mix to form a white emulsion. The seal on the water pump side is of the mechanical type which bears on the rear face of the impeller. The second seal, which is mounted behind the mechanical seal is of the normal feathered lip type. The oil seal is available separately, while the mechanical seal comes installed in the pump and is not available on its own. If on Inspection the drain shows signs of oil leakage, remove the pump and replace the oil seal with a new one. If the dram shows signs of coolant leakage, or a coolant/oil mixture in the form of a white emulsion, remove the pump and replace it with a new one. Refer to Chapter 3 for details.
6. Check the radiator for leaks and other damage. Leaks in the radiator leave tell-tale scale deposits or coolant stains on the outside of the core below the leak. If leaks are noted, remove the radiator (see Chapter 3) and have it repaired or replace it with a new one.
18.5. Check the pump drain hole (arrowed) for signs of leakage
Caution: Do not use a liquid leak stopping compound to try to repair leaks.
7. Check the radiator fins for mud. dirt and insects, which may impede the flow of air through the radiator. If the fins are dirty, remove the radiator (see Chapter 3) and clean it using water or low pressure compressed air directed through the fins from the inner side. If the fins are bent or distorted, straighten them carefully with a screwdriver. If the air flow is restricted by bent or damaged fins over more than 20% of the surface area, replace the radiator with a new one.
8. Cover the pressure cap with a heavy cloth, then remove the cap from the radiator filler neck by turning it anti-clockwise until it reaches a stop (see illustration). If you hear a hissing sound (indicating there is still pressure in the system), wail until it stops. Now press down on the cap and continue turning it until it can be removed. Check the condition of the coolant in the system. If it is rust-coloured or if accumulations of scale are visible, drain and flush the system and refill it with new coolant (see Section 28). Check the cap seal for cracks and other damage. If in doubt about the pressure cap's condition, have it tested by a Honda dealer or replace it with a new one.
18.8. Remove the pressure cap as described
9. Check the antifreeze content of the coolant with an antifreeze hydrometer. Sometimes coolant looks like it's in good condition, but might be too weak to offer adequate protection. If the hydrometer indicates a weak mixture, drain, flush and refill the system (see Section 28).
10. Install the cap by turning it clockwise until it reaches the first stop then push down on it and continue turning until it can turn no further. Start the engine and let it reach normal operating temperature, then check for leaks again. As the coolant temperature increases, the electric fan (mounted on the back of the right-hand radiator) should come on automatically and the temperature should begin to drop. If it does not, refer to Chapter 3 and check the fan and fan circuit carefully.
11. If the coolant level is consistently low, and no evidence of leaks can be found, have the entire system pressure checked by a Honda dealer.
12. On XRV750 models, check the oil cooler (located below the left-hand radiator) and its hoses in a similar fashion to checking the radiator and its hoses (see illustration). Refer to Chapter 2 for details of oil cooler and hose removal and installation if required.
18.12. On XRV750 models check the oil cooler (arrowed) as well