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Everything you need to know about motorcycle coolant

Which coolant is best? How do I inspect coolant level? – And other important questions answered.

Martin Asuncion Martin Asuncion on Apr 12, 2021
Motorcycle Coolant and KTM 390 Duke

Looking after a motorcycle is no easy feat given the number of parts and components that riders will have to maintain, replace, or keep healthy—which includes the fork seals, oil levels, clutch cable, throttle cable, fuel system cleaning, oil changes and so much more. As such, making sure that each and every component is in proper shape can be a bit difficult given the number of parts, specifications, and recommended brands that a rider will have to remember.

The motorcycle’s cooling system is arguably one of the more important items to look out for in this long list of motorcycle parts to look out for—and while the cooling system seems to be relatively straightforward at first glance, diagnosis and repair can often be a bit tricky when it comes to actual practice. If you’re delving into the world of motorcycle coolant and the cooling system, then you’re in luck. Here’s everything you need to know about motorcycle coolant.

Related:
Motorcycle Maintenance checklist and guide - everything you need to know

Checking level and topping up

KTM 390 Duke Coolant Level Indicator

When checking the coolant level of your motorcycle, the first thing to do is to make sure that your motorcycle engine is completely cold, unless otherwise specified by your service manual. This is to make sure that your hand is not at risk from hot steam or scalding fluids. Locate your coolant reservoir and look for the coolant level indicators. Ensure that your coolant is found between the lower and upper limits of the reservoir. If your coolant is overfilled, simply remove excess coolant.

However, if you find that coolant is underfilled, you will need to top up your coolant levels. Coolant is typically topped up through the reservoir and not on the radiator itself. The reason behind this is that the radiator must be kept airtight at all costs since air bubbles will expand through heat and cause premature overheating. When topping up make sure to use the same coolant brand or variant as what is currently inside your system. If you absolutely need to top up but do not have the right coolant on hand, you may use distilled water as a substitute for emergency situations.

When to flush your coolant

Husqvarna Svartpilen 401 Engine

If you’ve topped up your motorcycle with distilled water for an emergency, you will need to have your coolant flushed and replaced as soon as time permits. A full flush and replacement will also be necessary when your motorcycle reaches the recommended service interval specified by your manufacturer—but generally should be replaced every 1-2 years for safekeeping. If your motorcycle has over 15,000 kilometers on the clock, you might also want to consider doing a cooling system cleaning that makes use of a cleaning solution prior to the final coolant fill.

What coolant to use

KTM 390 Duke Coolant Fill

For topping up, it's important to stick to the coolant brand and specification already inside your engine. Mixing different coolant specifications and brands may cause more harm than good due to possible chemical reactions, which is why topping up with distilled water would be the next best-recommended course of action. However, if you’re doing a full flush service, it would be best to stick to the recommended specification of your manufacturer in order to make sure that the properties and chemicals found in the coolant can safely heat up and stay inside the engine.

My coolant still keeps running out

Husqvarna Svartpilen 401 Radiator Cap

If you’ve found yourself topping up more frequently lately, there may be a few things to check before your next ride out. First, inspect your entire cooling system and look for signs of the leak which typically look like white or grey surface stains. Start at the radiator and trace the hoses and pathways until you get to the engine. Inspect the radiator cap, drain bolts, and other surfaces. If you’ve found any specific area which contains the stains, it may be good to take your motorcycle to a shop to have that particular part serviced.

Radiator caps are often at fault when it comes to incremental coolant leaks so make sure that your radiator cap is also looking good and sealing properly. If for any reason your cooling system looks healthy after inspection and is still leaking fluid, it may be best to take your motorcycle to your service center for inspection and diagnosis. Due to the complexity of the cooling system, leaks can often manifest from different areas of the motorcycle—the external components such as the radiator or coolant hoses, or the internal components such as the water pump and engine gaskets. It would be best to have these items checked at a reputable service center to make sure your motorcycle will be running healthily in no time.

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