Classic Car Radiator Cap Performance Test

Important for a cooling system to work that all the components within the cooling system are working correctly. So for instance, we don't want a leaky system and we don't want a leaky radiator cap. So a device like this is a great thing to have, and we can test both the radiator system and the cap. What we can do here is put this cap directly on the neck of the radiator, use this to apply pressure. We can use that to see if there are leaks coming out any place.

One of the things I really like about this is that instead of running the engine, getting the fluid hot, and then poking my hands around under all those hot components, looking for leaks, I can pressurize it with this. The fluid is still cool. I can use that to check for leaks. Additionally, we can check caps. Now it's important that the cap is sealing correctly otherwise you can have the engine running a little bit too warm.

In order to test the cap the adapter has to go on top of that adapter looks like the neck of a radiator now, so the cap can go on there. You wanna know from the cap, from the, numbers on the cap, how many pounds that cap is designed to take. So this is a 16 pound radiator cap, that's gonna affect our test. Lock the cap on there just like we would if we were putting it on a radiator, I've got some water here what I had done was spritz the seal on that cap I moistened it just a little bit, That helps it sit inside our adapter. Now we're ready to pump this up and see what we get.

I'm watching the gauge on my tester here. I want the needle to hit the yellow over here that's my 15 to 16 PSI range. Once it's there that cap shall allow it to stay there, to hold that pressure for at least a minute. All right I'm solidly in the yellow there, I'm solidly in that 16 pounds. It's gotta be able to hold that pressure, then we know that that cap is good.

Now let me show you what happens when we have a cap that isn't good. So I'm gonna put this one on there It doesn't even look that great, but watch what happens when we pressurize this one. I can't get this to hold even an ounce of pressure as I pump this, that cap is absolutely shot. So an important check that you can do on your cooling system remember if we can check the cap, we can also apply this to radiator itself to check the entire cooling system, great device to have in your shop.