Try as I might yesterday and today, I cannot unscrew the black cap from the oilfilter housing on my pd-100 tdi engine. I've tried some belt wrenches, but there isn't any grip. I'm fairly sure that I'm not doing anything stupid, but just in case, I am correct in unscrewing the black cap with a clockwise arrow and 25Nm written on it to access the oilfilter? I know there is a specialist tool (http://shop.metalnerd.com/index.cgi MN341700 Specialty Socket for Oil Filters & Filter Caps) but I was wondering if there was any other way to get this cap off? It's driving me mad! Whoever was last at it must have welded it on. Cathal.