Keep things cool
Ten simple steps to replacing your radiator and coolant hoses
1 When rads go bad…
Right in the line of fire, your radiator takes some abuse. On older bikes, signs of a rad that’s past its best will be bent fins and repair patches, all of which degrade efficiency and could contribute to leaks. It’s a similar story with the hoses. If the components of your cooling system are in a state, then it’s high time you ordered some replacements.
2 Drain the coolant
Locate the coolant drain bolt, it is often found around the bottom of the water pump. Another method is to undo the coolant hose at the lowest point in the cooling system. Whichever way you do it, be prepared to catch the coolant in a tray. Undoing the radiator cap can help speed things up, as this allows air to enter from the top and lets the coolant run out faster.
3 Free the hoses
Undo the hose clips that attach the hoses to the radiator, then gently ease them off; if they are reluctant, use a skinny screwdriver with a squirt of WD40 to free it off. There will also be an electrical connection for the fan – undo this, then look for the temperature sensor on the radiator because this also has a connector which needs to be separated.
4 Wriggle out the radiator
The radiator will now only be fixed to the bike via its mounting bolts – undo these and then carefully move the radiator away from the bike. As you do this, be prepared for more coolant to pour out from the rad – this usually happens when you tilt it to avoid it hitting the front wheel or mudguard, so be on your guard as you ease it out.
5 Fit the old to the new…
Before you discard the old radiator, unscrew the temperature sensor and the fasteners that secure the fan to the rad, then fit all these components to your new radiator. Be aware that the temperature sensor will need to be installed with a new O-ring or washer.
6 Spot the shapes
Remove the hoses one at a time then lay them next to their equivalent replacement – sometimes the differences in shape can be quite subtle so take time to be sure you know which is intended to go where. When you’ve worked things out, offer each one up to the bike.
7 Look for kite-marked clips
It’s highly likely that the hose clips will need replacing too. It’s important to make sure that any replacement clips you buy are kite marked. Slide the new clips over the ends of the hoses then push the hoses onto the engine. Wiggle the new clips into place and tighten up.
8 No bad vibes please
Now fit the new radiator. You will notice that it doesn’t mount directly to the chassis, instead the bolts go through spacers that fit inside rubber dampers. This allows the radiator to be insulated from vibration. Make sure the dampers are in good condition and are fitted correctly.
9 Wire it up
Ease the radiator into place, install the bolts and hand tighten. Once all the fasteners are located, tighten them up fully. Next fit the hoses, using new clips as required. Rejoin the connectors for the fan and temperature sensor, making sure the wires are routed correctly.
10 Re-fill with coolant
Finally, fill the radiator with coolant and bleed the system of air using the process described in the bike’s workshop manual. As this can involve starting the bike and re-checking the levels once it has cooled down, be sure not to undo the rad cap when temperature is hot.