The thermostat seems to open more erratically than with the original. I'm using a 160 tstat and I don't remember the truck ever going over 180 with the stock pump. Now I'm seeing mid 190s. I'm wondering if maybe the thermostat bosses are machined differently on some of these aftermarket pumps and my 160 tstat isn't seating/ opening properly.

 

Maybe its the thermostat, or everything youve done to the truck!?

 

I was saying even after all the speed parts, the parts store pump seems to cool more erratically. Possibly still air in the system...I was just wondering if anyone had noticed something similar. I know Atomic said he was running a cheapie parts store pump without any issues, other than the pulley snout issues which are separate.

 

More likely sounds like an air pocket honestly, are you going off cluster or data?

 

Found my problem. Murray water pumps ftl. The thermostat inlet bore is oversized and off center. The tstat must have been binding and not opening properly. Stock pump is going back on, my leak was actually from the steam vent seals anyways.

Stock pump: ~21mm bore
Murray: ~24mm bore

The 160 tstats are obviously designed around a stock pump. Lesson learned.

 

I usually use bosch pumps for aftermarket alternative, and have never seen anything like that before... Thats slightly ridiculous