MXA WRENCH TECH: LIVING, LOVING & CARING FOR YOUR EXPENSIVE RADIATORS

May 16, 2013
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QUESTION ONE: WHAT IS THE BEST THING TO PUT IN A RADIATOR?

Special coolants are better than water (although water can be used in a pinch). Most coolants use ethylene glycol as the main ingredient. This alcohol-based fluid can raise the 212 degree boiling point of plain water by as much as 60-plus degrees. A coolant is also called an antifreeze, because it drops the freezing point down to the -80s. Inhibitors are added to coolants to control corrosion. Silicates aid in the lubrication of water pump seals. De-foamers maintain the consistency of the coolant as it’s being whirred around by the impeller.

QUESTION TWO: WHAT ABOUT DISTILLED WATER?

If you want to put water in your radiator, it is best to use distilled water. Distillation is a process that takes water and boils it. While the impure sediments stay down at the bottom, the steam vapor is collected. The liquid that is collected as vapor is the purest form of water you can buy. By using distilled water, you eliminate the impurities and hardness that scrapes, scars and corrodes the cooling system.

QUESTION THREE: HOW HIGH SHOULD THE WATER BE?

To the top. If the fluid level drops by even a small amount, start looking for the leak. The most likely places are head gaskets, hoses, the radiator cap or water pump seal.

QUESTION FOUR: WHAT DOES A RADIATOR CAP DO?

Since the boiling point of fluid is higher when pressurized, the manufacturer takes advantage of this by pressurizing the cooling system. The radiator cap keeps the coolant under pressure. If you think your bike has a cooling problem, the next step is to inspect the cap O-rings and gaskets for cracks. A broken gasket means the cap can release hot coolant out the overflow where it exits as steam. Even if no broken gaskets are found, the radiator cap is still suspect. Since the cap can’t be checked until you get back to the shop, resort to a process of elimination.

QUESTION FIVE: WHERE SHOULD TROUBLE SHOOTING START?

Overheating can be caused by a myriad of problems: a faulty impeller, coolant blockage, lean jetting, thrashed top end, bad coolant or a blown head gasket can all cause steam to be pumped out the radiator overflow house.

Starting from the top, anything that impedes the speed with which the coolant flows through the radiator will cause it to overheat. Old, contaminated coolant can have such a low boiling point that it will spew out the overflow when the motor is used hard.

If you have a water pump seal leakage, a quick check of your gearbox oil will tell you if water is leaking into the tranny. Oil with water in it looks like milk.

Finally, a blown head gasket can leak exhaust gases into the coolant and pressurize the system so much it triggers the radiator cap’s blow-off.

QUESTION SIX: CAN I KEEP RACING IF MY BIKE IS LOSING FLUID?

This is a personal call. If you haven’t found any obvious signs of a leak and the bike isn’t blowing steam out of the overflow hose when being ridden, you need to judge how far the coolant level dropped in the radiator. If you can’t see any coolant in the radiator, park it and have it fixed. If the level has dropped down to the top of the inner core structure, you could try to race, but first, borrow a radiator cap from a buddy, fill it up with water and have a friend signal you if it starts steaming.

QUESTION SEVEN: HOW DO I TEST MY COOLING SYSTEM?

Snap On sells a coolant system pressure tester. The Snap On cap replaces the OE radiator cap. Use the Snap On hand pump to inflate the system to the maximum pressure listed on the radiator cap. Coolant will leak from wherever the fault is. If fluid comes out the overflow before reaching the blow-off pressure, the radiator cap is bad. If the coolant system holds the maximum pressure for 10 minutes you’re fine. A good race shop should have a cooling system pressure tester.

QUESTION EIGHT: CAN RADIATORS BE WELDED?

Yes and no. A radiator repair shop can successfully weld a cracked tank or spigot, but leaks in the core are harder to deal with. The fin area is too thin to weld and epoxy hasn’t held up. The best way to repair a busted radiator is to replace it.

QUESTION NINE: WHAT ABOUT THOSE ROAD WARRIOR GUARDS?

Aluminum style radiator guards will protect a radiator from roost, tree branches and other obstacles, but they reduce air flow (and can raise engine operating temperature by 10 degrees).

QUESTION TEN: HOW DO YOU CLEAN A RADIATOR?

It’s easy with a pressure washer. If it’s between motos and there’s no washer within site, you resorts to good ‘ol elbow grease, with care. Make sure that dirt has not filled up the open spaces between the radiator fins. If you find dirt, remove the front louvers and shrouds. Take a soft bristled brush and skim the dirt off by brushing from side to side, in the same direction as the fins. If the radiators are packed with mud, first use water to splash off as much muck as possible.

The reason you don’t brush the radiators using an up and down motion or with a wire brush is that it’s easy to bend the soft, paper-thin fins. Smashing the fins closed restricts air flow just like plugging them with dirt.

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