How to change (and optionally flush) your coolant


Step-by-step tutorials on how to maintain and fix your GL1500
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How to change (and optionally flush) your coolant

Postby WingAdmin » Tue Dec 15, 2015 11:39 am



If oil equates to the lifeblood of your engine, I suppose coolant equates to perspiration: It's used to regulate the temperature of your engine.

The temperature of the burning fuel/air mixture inside the cylinders are extremely hot: as high as 1800°F / 980°C. Your engine is made of aluminum, which has a melting point of 1221°F, or 660°C. If that heat isn't removed rapidly, your pistons and cylinders will literally melt.

To achieve this, each cylinder has what's called a water jacket - a space around the outside of each cylinder, through which coolant can flow:

Water Jacket
Water Jacket

Coolant is pumped through this water jacket, and heat is transferred from the cylinders into the coolant. The coolant is then circulated to the radiators. The radiators consist of a series of thin tubes. Each tube has thin metal fins attached to them. The coolant flows through these tubes, and heat is transferred from the coolant to the metal fins. Air flows over the fins - either from a fan blowing (at low speeds) or from forward motion of the bike (at higher speeds) and heat is transferred from the fins into the air, which is dumped overboard.

Radiator
Radiator

So just what is coolant? Mainly, it is ethylene glycol, which is mixed with water. When ethylene glycol is mixed with water in a 50/50 mixture, the resultant fluid has a higher boiling point than straight water.

Boiling Point vs Water/Coolant Mixture
Boiling Point vs Water/Coolant Mixture

Adding more ethylene glycol actually lowers the ability to remove heat from the engine, due to its higher viscosity - the ideal fluid is straight water, which is why racing cars typically use water as coolant - but for an everyday vehicle, this is a bad idea, as we will see.

Heat Capacity vs Water/Coolant Mixture
Heat Capacity vs Water/Coolant Mixture

The 50/50 mixture of coolant and water also lowers the freezing point of the mixture considerably - instead of freezing at 32°F / 0°C, a 50/50 mixture will freeze at -40°F / -40°C! This is very important when storing your bike during the winter.

Freezing Point vs Water/Coolant Mixture
Freezing Point vs Water/Coolant Mixture

We also raise the boiling point of the coolant mixture by pressurizing the cooling system. The part of the system responsible for this is the radiator cap. As the coolant heats up, it expands - but with nowhere to go, it starts increasing the pressure. The radiator cap has a valve in it that opens when pressure reaches between 11 and 15 psi, and closes when it drops below that level. For every pound of pressure, the boiling point goes up by 3F - so a 13 psi increase boosts the boiling point of 50/50 coolant mixture from 220°F / 104°C to 259°F / 126°C. If the coolant's boiling point is reached, it produces massive amounts of steam and pressure, and this steam is vented out rapidly - the system "boils over" and the vehicle overheats.

Normally when the vent opens on the radiator cap, coolant flows out of the cap, through a hose and into the coolant overflow tank. When the bike cools off, the coolant contracts, and coolant is sucked back from the overflow tank and into the radiator, to keep it topped up.

There are a couple of other functions to the GL1500 cooling system. There is a thermostatic valve that opens at around 190°F / 84°C. When it opens, it allows coolant to flow to the rest of the engine, so that heat in other parts of the engine is removed as well. The engine operates best at a specific heat range, so coolant does not flow below that temperature, in order to allow the engine to heat up quickly to its ideal operating temperature.

Lastly, on the GL1500, heated coolant flows through passages in the bottom of the throttle bodies. This is used to warm the throttles quickly upon startup to shorten the time required to warm up the bike, and give consistent operation of the throttles. A thermostatic valve shuts off this coolant flow once it reaches 175°F / 80°C.

So it's important to have coolant in our bikes. What other functions does coolant perform? It has slightly acidic properties that chemically remove scale and deposits from the inside of the cooling system. This is particularly important for the radiator, where the very narrow tubes are easily clogged with deposits. Many coolants have "silicates" - basically sand, or sandpaper without the paper - to mechanically remove deposits. It is VERY IMPORTANT that you never use coolants containing silicates in your Goldwing - they will cause permanent damage to your water pump and seals!

This is also why it is important to never use tap water when mixing 50/50 coolant. Tap water contains many minerals and deposits, which will then be deposited on the inside of your cooling system, clogging it up. Always use distilled water only, which conains no minerals or deposits.

The process of heating and cooling over and over again eventually breaks down the coolant, and it needs to be replaced. It can become too alkaline or too acidic, and can cause damage or leaks to your cooling system. It's recommended that you change the coolant in your motorcycle every two years.

For this job we will need four quarts of quality coolant. I prefer to use genuine Honda coolant, to preserve the delicate seals on my water pump:

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It is already mixed 50/50, so you do not need to measure and mix it with distilled water. If you do use aftermarket coolant, make SURE it is acceptable for use in aluminum engines, and that it is silicate free:

Image

We will also need a funnel.


WARNING: Make sure the engine is COLD before beginning this process - opening a hot, pressurized cooling system will eject huge amounts of steam as the coolant instantly boils, and will cause severe scalds and burns!


1. To remove the fairing front cover, press inward at the center of the top of the cover. This will expose the posts seated in the grommets at the top corners.

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2. Gently pull the top corners away, one at a time, to unseat the posts from their grommets.

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3. Once both posts are unseated, remove the front cover.

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4. Remove the screws on either side of the under cover.

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5. While holding the under cover in place, remove the center screw.

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6. Pull the under cover away.

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7. Remove the ignition switch cover by gently pulling up at the bottom as shown until the posts disengage from the rubber grommets. Then release the tabs at the top and remove the cover.

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8. Remove the left top inner cover by pulling the tab free at the rightmost edge as shown.

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9. Follow by pulling each tab free in sequence until you get to the front tab.

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10. This tab locks in place - be careful not to break it. Next, remove the right top inner cover the same way as you removed the left side.

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11. Open and remove the radiator cap. This allows air in as we drain the coolant.

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12. Place a pan (at least 5 quart capacity) underneath the water pump at the front of the motorcycle, and remove the drain bolt as shown.

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13. Allow the coolant to drain into the pan. This will take a little while.

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14. Remove the coolant reservoir cap. Use a siphon, or my favorite method - a small hose duct-taped onto the end of a shop vac - to suck up the residual coolant from inside the reservoir. Pour some water into the reservoir and then suck that up as well. There will be slime and residue on the bottom of the reservoir, you want to suck up as much of this as possible.

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15. Once the coolant has finished draining, replace and tighten the drain bolt.

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16. Using a funnel, slowly pour in as much coolant as the bike will allow. You will likely only get 1 1/2 or 2 quarts in before it fills up to the neck - so be ready for it! Once it does fill up to the neck, let it sit for a minute until the bubbles of air work their way up, then add some more. Repeat this until you've got at least two quarts of coolant in. Turn the ignition on and crank the engine briefly. This will move coolant through the engine and radiators. You should be able to get another quart of coolant in cranking the engine like this.

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17. Start the engine and let it idle. You will see bubbles start to come up the radiator neck, and the coolant level will go down as the bubbles come up. Immediately as the coolant goes down, add more coolant to keep the level at the radiator neck as shown. Keep doing this as the engine warms up, until you've got all of the fourth bottle of coolant in the engine.

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18. While the engine is running, install the radiator cap and make sure it is tightened all the way. Allow the engine to warm up to normal operating temperature - at least until you hear the radiator fans come on.

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19. Remove the coolant reservoir cap.

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20. Fill the coolant reservoir, using the level gauge built into the cap.When the engine is at operating temperature, it should be between the two holes on the dipstick. When checking the coolant level during everyday operation, if it is low, you should add coolant to the reservoir (not the radiator). Shut the engine off.

Image

21. Lift the under cover into place.

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22. Insert the center screw to hold the under cover in place.

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23. Ensure the posts at the front, on the bottom of the lower cowls fit into the holes on the top of the under cover (visible at the front edge where the lower cowl and under cover meet) - on both sides! Once the posts are in place, replace and tighten the screws on either side.

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24. Make sure the tabs at the bottom of the front cover fit behind the ridge of the under cover, and that the tab on the bottom center of the front cover fits into the slot in the under cover. Align the front cover, then press the posts on either side into their respective grommets.

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25. Insert the forward tab of the left top inner cover into its slot in the dashboard.

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26. Work your way around the top inner cover, inserting the tabs into their slots, until you finish up with the tab on the inner part of the fairing top. Repeat to install the right top inner cover.

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27. Insert the top tabs of the ignition switch cover into the dash, and press the posts down into their rubber grommets.

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Flushing

In order to flush the cooling system, we will need a couple gallons of distilled water:

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After draining the coolant as described above, instead of filling the system with new coolant, fill it with distilled water. Run the bike to warm the engine as you would if it was full of coolant, then shut it off. Open the coolant drain and drain the water out into a pan - careful, it will be hot! Don't forget to also suck the water out of the coolant reservoir.

Image

Repeat this as desired, or until the water drained is clean. Once complete, fill the system with coolant as described above.



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OldZX11Rider
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Re: How to change (and optionally flush) your coolant

Postby OldZX11Rider » Tue Dec 15, 2015 12:46 pm

Thank you very much. Photos always make the written instructions a little easier to follow.
Especially for a non-motorcycle mechanic like myself. :D
For he is the minister of God to thee for good. But if thou do that which is evil, be afraid; for he beareth not the sword in vain:

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NVSB4
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Re: How to change (and optionally flush) your coolant

Postby NVSB4 » Tue Dec 15, 2015 2:09 pm

Another great and timely How-To, thanks
It's never too late to have a happy childhood!

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duesi06
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Re: How to change (and optionally flush) your coolant

Postby duesi06 » Mon Mar 21, 2016 4:56 am

You habe a very simpl and i think, a good working battey monitor in your pictures. Can you tell me where to buy?
Thank you.
Peter

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WingAdmin
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Posts: 17046
Joined: Fri Oct 03, 2008 4:16 pm
Location: Strongsville, OH
Motorcycle: 2000 GL1500 SE
1982 GL1100A Aspencade (sold)
1989 PC800 (wife's!)
1998 XV250 Virago (sold)
2007 Aspen Sentry Trailer

Re: How to change (and optionally flush) your coolant

Postby WingAdmin » Mon Mar 21, 2016 12:08 pm

duesi06 wrote:You habe a very simpl and i think, a good working battey monitor in your pictures. Can you tell me where to buy?
Thank you.
Peter


Not exactly the same, but it's similar to this one: http://cyclemax.com/inc/sdetail/heads_u ... /129/70605

JAcossey
Posts: 12
Joined: Wed Aug 27, 2014 12:16 am
Location: Manchester, TN
Motorcycle: 1997 Goldwing SE

Re: How to change (and optionally flush) your coolant

Postby JAcossey » Mon Aug 15, 2016 2:56 pm

You have the best how to articles I have ever read!! Very easy to follow. Thanks so much for your work and time.




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