Quote:
Originally Posted by glang
errr well actually on motorcycles (and my 50 yr old classic car) the coolant does flow back and forth to the expansion bottle. The rad is filled to the top so that as the temperature increases the volume of the coolant expands (a little) and would burst the rad if the cap didnt lift and allow the excess to go to the bottle. Then on cooling the volume reduces and coolant is sucked back to the rad via a small spring loaded valve in the cap (the caps for the two designs are quite different).
I think bikes use this older, poorer system because it avoids having a beefy expansion bottle with pressure cap and, on overheating, dumps boiling liquid to the expansion bottle not directly to atmosphere.
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I never fill my SVs rad to the top.I fill it to just below the neck.Always have done on all my liquid cooled Motorcycles and never had a problem.
Also you must have seen the coolant level drop when you have,"Burped" the system when changing coolant when the Thermostat opens so on a properly running Liquid cooled Motorcycle the coolant isn't actually near the top/Rad-Cap when the engine is running?
This is why the manuals state not to top-up the coolant when the engines are warm as it will be a false level and over-filled?