Radiator cap

[pjm8047]

Does anyone have a part number for a radiator cap that doesn’t work with a overflow system per 73?

 

[Tony Tee]

Does anyone have a part number for a radiator cap that doesn’t work with a overflow system per 73?

I looked on rockauto.Com. and they list the plain cap and one with a lever to release the pressure. They both regulate cooling system pressure . And the overflow hose either goes to a overflow tank or dumps overflow onto the ground. I think most cars came with overflow tanks after 1970.
You might be missing the tank?

 

[pjm8047]

I have a 71 roadrunner. 1973 was the first year of the overflow tank for Chrysler and each system had its own style radiator cap per the 1973 service manual. It also says in the manual do not use a standard cap on a recovery style system.

 

[Tony Tee]

I have a 71 roadrunner. 1973 was the first year of the overflow tank for Chrysler and each system had its own style radiator cap per the 1973 service manual. It also says in the manual do not use a standard cap on a recovery style system.

Ok. So maybe early 73 year cars didn't have a overflow tank? And later production did have ?

 

[steve340]

I do not know a part number but most caps for a brand (Mopar or other)have the same dimensions and similar pressure ratings. So a cap, say of an earlier car like a 1960's Dart would fit. I get these over here easily from local parts houses.
The only difference between the two styles of cap is the recovery cap will have a little valve in the centre of the bit that seals the water in the radiator. The non recovery will only have the mechanism to relieve over pressure only.
You are right is you used a non recovery cap with the overflow tank it would not work correctly.
It would not have the little valve to allow the tank to accept or return water to the radiator.

 

[Darter6]

Unless you are looking for NOS or a factory style, the difference between a recovery cap and a non-recovery cap is the recovery cap has 2 seals,inner and outer.The non just has a inner seal.Just a FYI.

 

[pjm8047]

So a recovery tank isn’t needed when using recovery style cap Long as you’re not losing coolant from overflow tube?

 

[steve340]

Yes that is correct.

 

[pjm8047]

So it is ok to have air in top tank of radiator? The after market tank I installed doesn’t fill but does loss coolant When i top it off and doesn’t run hot. Normal?

 

[MoparLeo]

The whole point of a recovery system is so that there is never an air pocket in the cooling system. If you fil a non recovery systems radiator to the top when it is cold, it will dump the excess coolant when it gets hot. The coolant level will always be below full when cold when you open the cap to check your level. Unless it is an oe type restoration, add a recovery system. ALL cars made in the last 40 plus years have them for a reason. The coolant is always full, runs cooler, less air, less corrosion. 16 lb cap. Always pressure check the cap. New doesn't mean it works.

 

[steve340]

Not quite sure what you mean but this may help:
Non recovery you need an air gap in the radiator to allow the water to expand when heated but not push the cap to excess pressure.
Recovery the radiator is completely full and the water expands in to the tank and back when the engine cools. The recovery tank is 1/3 to 1/2 full when cold.
When set up this way if the tank level drops you are losing coolant.

 

[pjm8047]

The whole point of a recovery system is so that there is never an air pocket in the cooling system. If you fil a non recovery systems radiator to the top when it is cold, it will dump the excess coolant when it gets hot. The coolant level will always be below full when cold when you open the cap to check your level. Unless it is an oe type restoration, add a recovery system. ALL cars made in the last 40 plus years have them for a reason. The coolant is always full, runs cooler, less air, less corrosion. 16 lb cap. Always pressure check the cap. New doesn't mean it works.

Do it matter what size that recovery tank is? All I have is a 14oz can

 

[MoparLeo]

The easy way to tell is to measure how much coolant it takes to top it off after it cools down. Anything over that amount will work, naturally it doesn't hurt to have even a little more capacity.

 

[pjm8047]

I just ordered a 32oz stainless tank.

 

[QuickBpBp]

I have a 71 roadrunner. 1973 was the first year of the overflow tank for Chrysler and each system had its own style radiator cap per the 1973 service manual. It also says in the manual do not use a standard cap on a recovery style system.

Overflow bottles were used before 1973. My 72 RR/GTX has one and it's a factory piece...