vehicle radiator question, it baffles me and i am very knowledgeable about car repairs?

Question

i have a very visible crack in my radiator, when i drive the vehicle it doesnt leak,, yesterday i drove this vehicle 500 miles on the freeway, it didnt leak,, it only leaks when i turn the engine off and it cool down,, i was thinking the heat probably close closed the crack, but wouldnt the pressure inside push it open,,

Answer 1

I guess that pressure of your radiator cap might have something to do with it. Even if it is rated at 14 lbs, it may be weak and if you had the cooling system pressure ckecked, it would leak.

Answer 2

You almost answered your own question. It seems that when it heats up and expands, it does seal the crack. Most systems pressurize to 15 pounds and this is apparently not enough to push it open. This is the kind of problem that gets me off my wallet, I would change it. I am assuming that this crack is on the plastic part of the radiator, hey keep some alternate transportation in the trunk(bicycle).

Answer 3

While the water pump is circulating the water the pressure would be less than when you stop in the first instant before it cools down but if the crack is visible it should leak unless you have added leak stopper at some time

Answer 4

I do not know for sure but probably the expansion by the heat is so tight only a small amount escapes under pressure--but beware-did you know if the crack opens while driving that anti freeze is very flammable and you could be engulfed in flames??

Answer 5

Are you sure you termostat is working right. some times it can be stuck open or closed and will do this. You might want to change that, they do get weak after a time.

Answer 6

http://www.permatex.com/products/automotive/specialized_maintenance_repair/radiator_fuel_tank_repair/Permatex_Quick_Solder_Radiator_Repair.htm

http://www.permatex.com/products/automotive/specialized_maintenance_repair/radiator_fuel_tank_repair/Permatex_Gas_Tank_Radiator_Repair.htm