Hi Gents... After a recent water pump replacement (one side) noticed a small but persistent leak...dammit! Tried everything on the planet to isolate it. In my case it is very hard to see; the motor is way down in the chassis (38 Ford) and very close to the radiator. I just didn't want to believe that a new pump was bad, it wasn't. Here's the deal: the stainless steel allen head cap screw that goes inside the WP inlet was bottoming out on the block. i.e. the screw was two threads too long. When the weight was put back on the front mount it was enough to seperate the pump and block just slightly. Evidently the new pump was slightly thinner than the old pump. Who'd of thunk it! Just saying...
Thanks for the heads up. Those bolts are blind. Hate em getting in or out. Best to just throw in a thick washer to take up the slack to be safe.
I used a SS allen head cap screw and a ss lock washer. There was no way to actually see if the lock washer was made completely up...just used what i thought was an average size bolt. I just ran the whole process thru my mind and I knew the block was clean and the suction side hose was good (pressured it up) all the other bolts were tight with the washers made up. Gasket was new & the only thing left was the lower bolt. Also since there is a lot of weigh on the pump and I couldn't verify the lower bolt was actually tight. Soooo out came the water and the bolt and off came two threads. Problem solved. Like my daddy said, "even a blind hog can sometimes find an acorn"!
Here's another strange one. Chased an overheating problem forever. Finally pulled the water pump and found the impeller was a loose fit on the driveshaft. So, the next time you are installing a water pump, grab the driveshaft with one hand and the impeller with the other hand and give 'em a good twist in opposite directions to check for a press fit.