I finally got tired of my radiator leaving its mark and installed a recovery tank. My question is: what is the proper cap to use? I have a 16lb vented cap on there now and it appears to be doing its job; although the system only gets pressurized when it is real hot. Any thoughts? Thanks

Another picture of the tank

The cap should have a rubber seal to do its job. Some caps are for recovery tanks and some are not. Also when using a recovery tank the radiator should be full. Mike

Both of the caps have rubber seals; one has the bottom disc free floating and the other the disc is spring loaded closed.

I am referring to the radiator cap itself; I believe I have the correct one (vented) as it is the same cap as my D150 1977 with a coolant recovery system. As far as being pressurized; it now does so in a few minutes after I put the new cap on.

The level of coolant in the overflow bottle will rise when your engine gets hot and retract when it cools. If the radiator cap sucks air the recovery system won`t work. The overflow tank must be vented. The radiator needs to be full and have some coolant in the overflow tank from the start. Mike

In the picture above it looks like the overflow hose is going in the other direction????? I`m not seeing how it connects to the tank. I have never used that type so I`m not familiar with how it works. IMO, I would get a OE type cap not the lever type. mike

Mike the system works great; coolant tank is vented and the cap allows the coolant to enter the tank when hot and, as advertised, it syphons the coolant back into the radiator when it is cooling down

Mike, the hose goes down the side and under the radiator to the bottom of the coolant recovery tank.

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Mike the system works great; coolant tank is vented and the cap allows the coolant to enter the tank when hot and, as advertised, it syphons the coolant back into the radiator when it is cooling down

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I`m not really sure what you are asking? Mike

You will always have some pressure when running. That`s how the system works. With a 16 lb cap the pressure will release into the tank when it gets above that. That`s why you don`t open the radiator cap until the car cools down. Mike

Read the 4th post again; one cap has a free floating disc and the other the little disc is spring loaded. It appears that the spring loaded type will only relieve any air or coolant only when the cap reaches 16lbs. The other is free floating allowing air and coolant to escape before reaching the 16lb point and once the coolant is hot enough the disc will seat. My question was which was preferred for a coolant recovery system. The one I have installed now works good and it has the free floating disc on the bottom.

Heres a pix of the non vented type cap (disc spring-loaded closed)

Vented type (disc hangs down with no spring loading)

Spring loaded cap with the rubber seal like shown in the first pic is the one that is used with recovery systems. They do make a non recovery type cap with a brass ring instead of the seal for cars with out a tank. Mike

I just got one of those fancy Thermo-Caps and it has a spring loaded disc. I was skeptical if it would work on a recovery system but it does.

http://www.accel-ignition.com/ProductDet...p;minselection=

Goes against everything I ever learned, recovery systems should use the "dangling disc".

I would just get a closed system cap. Both style caps will hold pressure until rated psi release point, but the closed sys cap will allow coolant to be drawn back into radiator when radiator cools and actually uses slight vacuum to pull from overflow jar back into rad.