I think it was only less than a year ago that I changed the yellowed out original Volvo coolant resevoir and replaced it with a SAMER brand one. Well, today as I was checking the oil and other stuff under the hood, I decided to check on the coolant. Before I unscrewed the cap (SAMER brand also), I decided to turn it clockwise just to see if it had loosen or something. I was able to turn it just a tad bit, but it made a hissing sound. So I opened it, checked around and screwed the cap back on. Now, usually I'm very careful about screwing it back on, making sure that it sits evenly on the resevour top. As I was tightening it, I realized the cap sorta went uneven, so I unscrewed it and tried again. Same thing. The cap will keep on turning and not sit tightly. Thought it was the cap. Good thing I still have the original Volvo resevoir, so I tried the cap on it and it screwed on just nicely. So the culprit now is the SAMER resevoir itself. GRRRR. This means I have to get a new tank and redo this thing all over again! *sigh* I'm tempted to get another aftermarket brand just because of the price, but I think I will have to get the OEM VOLVO resevoir plus a VOLVO cap to match. Has anyone had this happen to a SAMER coolant tank with the screw part of it? It wasn't like I messed with the coolant cap often. Btw, I can't use the old Volvo resevoir since it's in really bad shape.

edit to add: so I supposed it's not safe to drive with a resevoir cap that is not properly screwed on tightly?