Flow from Water Pump To Heater

**johngoodman** · 12-16-2009, 07:23 AM

On the LS1 engine water pump there are two fittings for the heater. One is 5/8" and the other is 3/4". The smaller one is the feed TO the heater, right?
John

**Goldcuffs** · 12-16-2009, 01:55 PM

Originally Posted by johngoodman

On the LS1 engine water pump there are two fittings for the heater. One is 5/8" and the other is 3/4". The smaller one is the feed TO the heater, right?
John

They both go to the heater core.

**johngoodman** · 12-17-2009, 05:50 AM

Originally Posted by Goldcuffs

They both go to the heater core.

I guess I didn't phrase it right. I know they both go to the heater, but I need to know which direction the water actually flows. The reason is that my foot will be very close to one of the connections and I will be unable to move it. I want to put an emergency cut-off on the the one that is pumping hotter water into the heater.
My assumption is that the smaller fitting feeds water and the larger returns it.
John

**9T8W66** · 12-17-2009, 06:14 AM

If I'm not mistaken the upper hose (at the heatercore) is In the lower hose is Out

**Cutlass** · 12-20-2009, 04:35 PM

I looked at a LS power truck the other day when I replaced a water pump and I think the smaller hose feeds the heater core and the larger is the return.