Hey there. Thanks for the quick reply. That's good to know about the oil as it saves me forking out hundreds of dollars to flush it all.
My guess is that the slimy build up was diesel bug but I'm not sure. Pic attached. I called the guy I bought it from and told him of the issue. He suggested...
I recently acquired a Case IH 454. Mostly been good but has given intermittent hydraulic issues e.g. bucket won't lift. The guy before me changed (or got someone to change) the hydraulic fluid and (I assume) put the right stuff in there.
When I purchased it I thought it was low on hydraulic...