SV650.org - SV650 & Gladius 650 Forum - View Single Post

glang · 23-07-18, 08:44 AM

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.

23-07-18, 08:44 AM	#13
glang Member Join Date: Oct 2007 Posts: 537	Re: Cooling fan 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.