I am looking at purchasing a Cat 311B excavator with a mechanical thumb. Any advice would be appreciated. It is a 1997 with just short of 4,000 hours. The present owner purchased it when it was 6 months old and now getting out of the business. I looked it over and couldn't see anything broken, no welds on anything, no major leaks, and all the bucket and boom pins look tight. I am painfully ignorant of what to look for as I think about buying this machine. I have 2 farm building sites to take out and if it held together for that, it would be better than half paid for. I have a D7E to go with it and I thought the 2 might work well together. Thanks for any advice you can give me.

See if the owner will let you dig a hole with it. If it digs good the engine has power and hyds are good and set up right. Push down with the stick vertical, bucket flat on the ground and make sure it will lift the machine up off the ground. Then travel it around in a circle for 10 minutes. If there is a leak in the hyd swivel down to drive motors it will stop driving in a circle and only move going straight.
Later Bob