Vehicle is a 2000 Bravada, driven 1-2 times a week for short 15 min trips. This is my mothers car and of course, she is not car savvy and doesn't pay attention to things like the rest of us. She called to say the car no longer has any heat. I thought maybe a plugged heater core as I have never touched that. So I back flushed it but not a lot of gunk came out. Hooked it back up and noticed the coolant was low. How low and for how long, I had no idea. Ran to Napa and got some dex-cool, put in half a bottle. Drove it for 5 min and got little tiny blips of minuscule heat. Came back and immediately smelled burning coolant. My heater core hoses aren't leaking but I had a nice puddle underneath, coolant all over the passenger underside of the motor. Looked on top of the motor and saw this fresh coolant leak. you guys think its the lower manifold gasket? Thanks

 

Yes. That area is VERY prone to problems as there is no passage through the lower intake manifold and, as a result, junk likes to collect in that area of the head/gasket. Hopefully the LIM isn't too pitted. If it is, put a decent coating of RTV over the cleaned surface only in those areas where there is excessive pitting. Put it together and follow the torque specs! Also make sure you get the updated, metal framed gasket set. The originals had a reinforced nylon frame that didn't get along with water too well. Nylon likes to swell & crack when subjected to too much moisture and even though the nylon should not be in the coolant path, once a small leak develops, it goes down hill fast.

 

Thanks!

 

Here is a good reference for the repair.

How To Replace Intake Manifold Gaskets On A GMC Jimmy 4.3 Liter V6 To Fix A Coolant Leak - GM Truck Engine Repairs