imported post
imported post
Your rad cap has 2 valves in it.
When the engine gets hot the coolant gets hot and expands.
If the level is proper(your rad will be full to thebottom of the rad capwith no air in the system anywhere).
So......as the coolant heats up it will expand . The rad cap has a pre set pressure regulation system consisting of a spring and a rubber seal. As the coolant expands it will overcome the pre set pressure that the cap is set at and will open the rubber seat and coolant will flow into your overflow tank. This increase in pressure in the cooling system causes the coolant to have a higher boiling point(water boils at 100deg F) with this increase in pressure the coolant can reach temps of about 200deg F before it boils.
Next thing that happens is that after your great day's ride u go home and park your trusty steed in the locked and secure garrage where it will not get stolen. As it sits there, the engine and coolant cool down. As the coolant cools down it contracts (the pressure goes away). The rad cap has a second valve in it that allows for this contraction of the coolant. As the coolant retracts it trys to create a vaccume in the cooling system, this second valve now opens and allows the coolant in the resevoir to return back into the radiator and keep the cooling system full of coolant and free of air.
If you do not keep the resevoir full you will get air into the system when ever the coolant cools off. Air, bare metal and moisture will cause corrosion, this is why u don't want air in the system.
If u find your engine boils out the coolant every time u ride it, thefixcould be as easy as replacing the rad cap(They do wear out)
If u find that after your engine cools down that any of your rad hoses collapse..the vaccume valve in the rad cap is not opening and not allowing the coolant to return to the rad from the resevoir(it creates a vaccume in the cooling system)
So back to the question....
When HOT the coolant level in the resevoir should be at the TOP mark
When COLD the coolant should be at the lower mark.
Sorry for the long post....... and rad caps work the same on ALL engines, diesels,2-strokes, 4-strokes,cars, trucks, boats, trains, motorcycles..............
Do u know what the differance is between a Harley and a Kenmore vaccume cleaner?
The position of the Dirt-Bag :hb:
