[edwhite7]

For me the holes were just to keep air from collecting behind the t-stat. It is designed to sense water and air can cause the temp to go way high before it finally opens. After it opens it can then regulate normally. This tends to happen in cars with t-stats mounted at the top of the system, they collect air. I believe that the bypass is keeping the water from being pumped through the expansion tank and then the radiator. It is just to far and easier to bypass. I am sure that there is a good reason for the bypass but my car will overheat in traffic with it connected. If I sat more than two or three minutes at idle I would turn the heater on and after it passed 220 F I would have to shut it off and leave the fans running. I would bump it over without starting to get new water into the heads until the temps came down. Those were the days, water wetter made a big difference and now I never think about it. The car has been on the road more than 20 years and has never overheated.
I originally cut through the existing hose and worked it off without removing the pump. I was able to slip some hose caps on and clamp them with worm clamps. After I was convinced that it worked I removed the pump and plugged the ports with some pipe plugs.