ecohen2
True Classic
Over the weekend I discovered that not all Stants caps seal equally well. Here is what happened...
During the past year, I swapped out my plastic stock tank for a stainless steel tank. The first tank had a leak, so I returned it but I kept the cap that I purchased with it. The second replacement tank has the same depth neck as the plastic tank and came with a 13 PSI Stants cap. This gave me 3 caps to play with although one of them was a 7PSI. Ever since I replaced the tank, I noticed that it never made a hissing noise when I removed the cap and that my temps would run higher than I expected. Yesterday I was thinking about how could the system lose pressure but not leak any coolant? What I discovered was that both of the Stants caps seal properly on the cap part, but one of them didn't seal against the inside of the neck. The result was the coolant would boil and I would eventually get air bubbles in the system without ever losing a measurable amount of coolant. I even did a pressure test and never found a leak in the system, but couldn't figure out why I had no pressure.
The two 13PSI Stants caps are both new, identical part numbers, appear to measure the same but the spring on the bad one seems to be cut a little short which is why it doesn't seal properly. My guess is that it is 1/8th of an inch difference. You don't feel any spring resistance at all with the bad one until the cap is almost tight. On the good one, you can feel the resistance as soon as you start turning the cap.
Just a seriously weird problem...
Ed
During the past year, I swapped out my plastic stock tank for a stainless steel tank. The first tank had a leak, so I returned it but I kept the cap that I purchased with it. The second replacement tank has the same depth neck as the plastic tank and came with a 13 PSI Stants cap. This gave me 3 caps to play with although one of them was a 7PSI. Ever since I replaced the tank, I noticed that it never made a hissing noise when I removed the cap and that my temps would run higher than I expected. Yesterday I was thinking about how could the system lose pressure but not leak any coolant? What I discovered was that both of the Stants caps seal properly on the cap part, but one of them didn't seal against the inside of the neck. The result was the coolant would boil and I would eventually get air bubbles in the system without ever losing a measurable amount of coolant. I even did a pressure test and never found a leak in the system, but couldn't figure out why I had no pressure.
The two 13PSI Stants caps are both new, identical part numbers, appear to measure the same but the spring on the bad one seems to be cut a little short which is why it doesn't seal properly. My guess is that it is 1/8th of an inch difference. You don't feel any spring resistance at all with the bad one until the cap is almost tight. On the good one, you can feel the resistance as soon as you start turning the cap.
Just a seriously weird problem...
Ed