1Bad70Convert

Hey Guys... Anyone have an extra 3859326 undated Water Pump for sale (GM 1-4 only and 1/2" unsleeved output)? I prefer a rebuildable core but will consider a rebuilt part if it has the correct cast iron impeller. Not looking to build for resale. I need one for my own use. Thanks in advance.

Westlotorn

This is a 25 year old TRW Water Pump, sold by TRW but I do not remember who made them for TRW. It has the Positive displacement impeller. You can see the difference between this and the paddle wheels already shown.
This type is used in all Diesel applications and all Heavy Duty gas engines. A 350 in a Dump Truck would have this type pump factory stock. It does not increase the speed of your flow but it does increase the pressure in the flow to make sure it moves uniformly in all circumstances while running.
I learned this lesson the hard way back in the early 90's. My 6.2L Diesel Suburban needed a new water pump, I bought one locally, a name brand and installed it, when I installed it I noticed the impeller was stamped steel and the stock WP had a cast impeller like the one pictured.
I scratched my head but went ahead and installed it. In a week I had scuffed one of my rear pistons, farthest from the water pump. After rebuilding that 6.2L I bought another new water pump from another name brand and it was just like my OEM pump with the cast impeller.
It was a hard lesson to learn. The stamped steel impeller just did not push the coolant hard enough to cool when I worked it hard, I was towing a hill when I scuffed the piston. The Stamped steel worked well enough to make me think all was just fine before leaving fully loaded on a vacation towing a heavy trailer. After the engine rebuild but with the new factory type water pump the truck had no issue pulling the same hill with the same load.
Lesson learned. A good friend and Machine Shop owner said he has seen that before and could have told me if I asked. I would name the names but after 25 years I could tell you I looked at 3 name brand pumps and only one had the factory cast impeller but I don't remember which of the 3 had the right cast impeller and which had the stamped steel.
PS: This impeller is just slightly recessed inside the pump, I did not measure that distance when I had it apart.