coolant leak

[Sonoma]

Have lurked for awhile but need some info

 

97 Sonoma - leaking got worse - released the cap part way and didn't leak much - kept a watchful eye on the fluid level until I was able to find the leak.

Drivers side of radiator at the lower left is a line coming out and heading back into engine (can't see where)- I pushed in on the line and it leaked worse - found that the locknut (?) was loose - tightened it up and no leak - yet!

 

What is the line? (I'm thinking transmission cooling?) and how does the line stay in place - radiator pressure and the locknut secures it ?

 

I've delayed this problem after a search of this forum - you guys got me scared it was my intake and then where I saw the leak - thought it was my radiator - if this was the only thing wrong - I'm real happy!

[YoungsterTech]

if its an auto trans cooler line, there should be a spring metal retainer on that nut that screws into the radiator. very small clip

[luthor]

Possible reasons of a coolant leak: Coolant leaks often occur at the water pump shaft seal, it might be a blown head gasket, leaking water pump, radiator, heater core, hose.. have it checked...