1998 gmc yukon

I have a coolant leak that i thought was the water pump. After replacing it I found out that I was wrong. As I was filling the radiator back up with coolant after replacing the pump, I got about 1 1/2 gal. of coolant in and it started pouring out what seems to be from a line running back towards the trans on the driver side. Can anyone help me with what this line is or maybe is?
Thx

If you have a rear heater option (controls for heat in back seat?) then it is probably the line that runs to the rear heater core- that has corroded through...and needs replaced.

Agree, leak somewhere going back to rear heater core. I'm in Arizona, and on my 1994 Suburban I had such leak on passenger side, underneath the running board, one of those wonderful GM proprietary fittings. Since I really did not need rear heat, I went to O'Reilly and asked to walk through their molded heater hoses; found a U-shaped one that went on with regular hose clamps and bypassed the rear system, worked fine.

I sold that Suburban in 2010 so not sure I could dig up that part number readily though.

If you have a rear heater option (controls for heat in back seat?) then it is probably the line that runs to the rear heater core- that has corroded through...and needs replaced.

No rear heat, but thanx for responding.

Agree, leak somewhere going back to rear heater core. I'm in Arizona, and on my 1994 Suburban I had such leak on passenger side, underneath the running board, one of those wonderful GM proprietary fittings. Since I really did not need rear heat, I went to O'Reilly and asked to walk through their molded heater hoses; found a U-shaped one that went on with regular hose clamps and bypassed the rear system, worked fine.

I sold that Suburban in 2010 so not sure I could dig up that part number readily though.

No rear heat, but thanx for the response.