RC-15 radiator cap

[Michael J.]

I am trying to get all the parts right on my '67 L71, and have replaced the radiator cap to what it should be, an RC-15. But, though the cap fits OK and turns to lock, it seems very loose. I notice the top seal on the cap is a thin brass sleeve, as opposed to a thicker, rubber type material on the RC-26 I have on my '66 L79 (expansion tank). The bottom seal below the spring seals fine, but the top is loose as you push it down. My question is is this normal, or should it seal tighter up top? The RC-26 seals much tighter, but maybe on a big block radiator the seal should be looser? Any ideas are welcome.

[Joe L.]

Re: RC-15 radiator cap

I am trying to get all the parts right on my '67 L71, and have replaced the radiator cap to what it should be, an RC-15. But, though the cap fits OK and turns to lock, it seems very loose. I notice the top seal on the cap is a thin brass sleeve, as opposed to a thicker, rubber type material on the RC-26 I have on my '66 L79 (expansion tank). The bottom seal below the spring seals fine, but the top is loose as you push it down. My question is is this normal, or should it seal tighter up top? The RC-26 seals much tighter, but maybe on a big block radiator the seal should be looser? Any ideas are welcome.

Michael------


Once turned to the lock position, the cap should be tight. In this respect, there is no difference between the fitment of an RC-26 on an aluminum supply tank and an RC-15 used on the filler neck of copper-brass radiators.

[Michael J.]

Re: RC-15 radiator cap

Thanks for the info, I was afraid of that. Seems odd because the radiator is original based on the numbers and stampings, and the cap is a repop but looks in great shape. Guess I will just have to use the cap as a show piece for judging and replace it for driving.