Overflow Tank question

[Eyvazk]

Guys- sorry for bringing the old topic here. Just got a replica 66 Cobra. Completely new to these cars. I noticed the radiator has a very small leak from the bottom passenger side after I run the engine. No leak while the car sitting in garage. I checked the white transparent canister, and no coolant in that - whether the engine hot or cold. I also opened the cap on the flexible hose (when cold) at the top of engine from thermostat to radiator and checked and noticed no coolant in the hose. Maybe it should be this way when the engine is cold. Anyway, my question is- should I add coolant to the engine and to what level. I am being told that transparent canister is just a catch can, unlike traditional cars with Min and Max marks… basically you shouldn’t expect to see coolant in there under normal circumstances. So then how do I know how much coolant should I add. Thanks in advance.

Originally Posted by timsullivan

Yes, you're right, the plastic overflow tank mounted on the right side fender well undoubtedly is the only source for the cooling system to literally and figuratively blow off some steam. Most likely you have the expansion tank (that sits directly above and in front of your thermostat housing) overfilled. They should only be filled to the midpoint of the expansion tank when the car is cold. That or you have some very serious overheating problems going on. Normal cooling system pressure relief shouldn't see water coming out of that very tiny breather hole on top of the overflow tank unless you have the puppy filled to the brim! Drain it all out of the oveflow tank and reset your coolant level in the expansion tank to the midpoint.

The valve on the bottom of the overflow tank should only move about 180 degrees to open or close the drain. If memory serves me it's just a press fit into the bottom of the tank.