ZX-6R Maintenance: Change Coolant

The bike in these photos is a year 2000 ZX-6R.

Warning

I am not a mechanic or a representative of any motorcycle or tool manufacturer or anything else official. This page is only my notes on doing this procedure myself. Although I believe what I have documented here is correct, I make no promises and you do this at your own risk.

Objective

Changing your antifreeze is one of the regular maintenance tasks specified in your service manual. (My manual says every 2 years or 24,000 Km.) Also, if you attend a track day, you may be required to replace your coolant with water to avoid spilling the slippery glycol on the track. The procedure is the same.

Required

Tools Required

• Rear stand (recommended)
• Phillips screwdrivers
• Hex wrenches (metric)
• Socket set (metric)
• Container to catch old coolant
• Funnel

Parts Required

• Antifreeze of appropriate kind
• Distilled water — a couple of 4-litre jugs

Difficulties

Some difficulties could be:

• Under-tightening (so it falls out) or over-tightening (stripping threads) the water pump drain plug. That’s why a torque wrench is highly recommended.
• Handling spilled coolant. It’s slippery. It’s very poisonous. Worse, it has a sweet scent that can attract household pets to lap up a spill.
• Disposal of your used coolant. Your city may have regulations on how to do this.
• Danger of burns if you remove the radiator cap from a hot engine (don’t).
• Danger of leaving an air bubble trapped in the system, lowering cooling efficiency.

Procedure

Putting the bike on a rear stand makes this job much easier, by creating some extra ground clearance underneath and by levelling the bike and holding it steady.

Remove the upper and lower fairings

You need to remove the lower fairing to access the drain point. Although it’s possible to reach the radiator fill point without removing the upper fairing (if you have a very long-necked funnel and small hands) it’s much easier to do this job if you also remove the upper fairing.

Drain the old coolant

You’ll be draining the coolant from the water pump, on the lower left side of the bike, just in front of the shift lever.

Make sure the engine is cold, then remove the radiator cap so air can enter the system from the top.

I usually put a spare pail under the filler cap to catch drips, as liquid will spill out.

Warning: Coolant is very poisonous. The glycol makes it taste sweet, so if it’s spilled on the floor, your household pet may lick it up.

On the left side of the bike, remove the drain screw from the water pump.

Let the coolant drain out completely, into a clean container. (If you’re removing it to put in water for a track day, you can reuse the coolant later.)

Flush the system

The trouble is that, even after the flow stops, you haven’t got all the coolant out of the system. It will be pooled in a variety of low spots.

Remove the thin hose from the overflow tank and allow the overflow tank to drain too.

Next, note this hose is lower than the drain point, so it will have coolant in it. Loosen the hose clamp, remove the hose, drain it, reattach it, and tighten the clamp again.

Next, flush the system by replacing the drain screw, filling the radiator with clean filtered or distilled water, running the engine for a few minutes, then draining the system again. Repeat until the water coming out shows no sign of colour. This usually takes me about 4 or 5 flushings.

(Oops. I forgot to take photos of this process, but you just fill, run, drain, fill, run, drain, until it comes out clean.)

Add new coolant

Tighten the water pump drain plug properly now.  It isn’t very tight (a soft metal screw, it will strip easily).

Mix coolant as specified on the jug. On mine, it calls for a 50-50 mix of coolant and distilled water. (If you’re setting up for a track day, you’ll be putting in pure distilled water, possibly mixed with “Water Wetter” if the organizers allow it.)

Fill the radiator to the top, and the coolant overflow tank to the line, and start the engine. As it runs, gently tap and massage the various coolant pipes to encourage any trapped air bubbles to rise out.

Keep running, with the radiator cap still off, until you can see that the coolant pump is running and circulating the coolant (you’ll see a current in the coolant visible in the top of the radiator). Massage those pipes again to be sure there’s no trapped air.

Pressure test and top up

Now stop the engine, put the radiator cap on and properly tighten it, and start the engine again. Watch the temperature gauge as the engine warms up.

Somewhere around 103 degrees Celsius217 degrees Fahrenheit you’ll hear the electric fan kick in. Shut everything off and let the engine cool down on its own. Now you have completely cycled and pressure tested the new coolant. Top up the coolant overflow tank to the line now. (Not the Radiator — don’t open it on a hot engine.)