Re: 1937 120 Water pump Packing nut - How tight?

Posted by TxGoat On 2023/11/9 20:18:28

If you over tighten much, it can burn out the seal and perhaps damage the shaft. If it's a little too tight, it will wear the seal faster than normal.
I'd tighten it in small increments until the drip stops, then wipe everything dry and run the engine a few minutes, then recheck.
If you have any evidence of a leak at that point give it another 1/4 turn or less, wipe dry, and try again. At that point, if the leak has stopped, I'd let it be. I'd want to check the coolant level frequently for the first few dozen miles, and give the nut another 1/4 turn or less if needed after 40-50 miles. I'd also re-oil the pump after about 50 miles or a few days.
Once the seal seats, it will usually need little attention for quite a while, but I'd look at the pump and check the coolant level every time I checked the oil, or every few hundred miles. If a drip develops after some usage, a fraction of a turn of the nut will usually stop it. If not, either the seal packing or the shaft bushings are worn out. A pump with worn bushings cannot be kept from leaking. See owner's manual and shop manuals for pictures and lubrication schedule and adjustment advice, including belt adjustment. There is a hole in the fan pulley about the size of a dime for oiling the front water pump bushing. With the hole straight up, the oil port can be accessed.

Important!! Avoid overtightening the belt! It's best to run it a little on the loose side for 50 miles or so with a new or rebuilt pump. An overtight belt will rapidly wear out the pump bushings.