How to replace motorcycle coolant
This is an overall review of how a water-based motorcycle cooling system works. Special emphasis is placed on how to burp the cooling system so that air pockets in the cooling jacket will be mostly evacuated before the engine overheats. The risk of permanent engine damage from an inadequately burped cooling system are discussed. The mechanism by which the radiator cap works in a closed cooling system is also discussed.
Ethylene glycol, the most common constituent of antifreeze, will last a very long time. However the anti-oxidant additives contained in modern coolants are depleted much more quickly, and harmful impurities can build up in the system and damage sensitive engine parts. So, coolant should be replaced at regular intervals. The 1995 VN800 Vulcan manual calls for replacement of motorcycle coolant every two years.
To understand how the radiator cap draws fluid from the coolant recovery tank into the main cooling system, watch this video.
If you are bewildered by the wide selection of coolants, and worried about mixing different types of coolant, watch the following video.
For a discussion of how an automotive water pump works, and an inside look at the weep hole, watch the following video.
This is an amateur demonstration done for entertainment purposes only. The video comes with no guarantees as to safety or accuracy, and it is NOT a qualified instructional video. Before deciding to work on your own vehicle, search for information from multiple sources and consider involving a professional. Motorcycle repair is a potentially dangerous activity, and complication are to be expected and planned for.
Thunderclap sound used under Creative Commons 3.0 license, done by RHumphries at http://freesound.org/people/RHumphries/