so today I checked my coolant and added some filtered tap water. as I was about to put the cap back on I noticed a couple pieces of small rubber bits. I looked under the cap and saw that they came from the rubber gasket/seal that's inside the cap. the seal did not look all torn up; it was more just a tiny tear, otherwise the seal looked pretty okay. I take it that this seal is used to seal tight the resevoir expansion tank. I did notice a slight hiss as I loosened the cap, the noise of which I understand is normal and means that the cooling system is keeping pressure.

anyhow, seeing the rubber bits made me decide to finally get a new cap, which I've been meaning to do because it is a bit used. I called the dealership to see how much they charged. roughly $26 something plus tax. then I called my local parts yard, which specializes in volvos. $10 for a used one. I decided to go online and try ipd since they have my ordering info. $7 something--cheap, but I knew this cap can't be that much. I decided to try fcp after hearing good things about them from y'all. $4! I decided to get an o/d relay while I was at it, since I've been meaning to get one anyway. I love saving money!