Howdy all! 1999 Dodge Ram, 5.9 Liter. In July I changed the heads, did a Hughes plenum fix, complete Felpro gasket kit, cleaned the Air valve and throttle body, new head bolts, tune up, etc. Basically the top end. The truck runs great. No misfires to speak of. Now, the truck is leaking coolant from the exhaust. Odd to me, because the engine runs fine, spark plugs are clean and dry, no coolant in the oil, and no oil in the coolant. This seems to have started when I changed the heater core. I think that was a coincidence, since there is no logic connecting the two issues. The water is leaking (onto the ground) from the joint of the exhaust manifold and Cat. At first, it was a tiny, intermittent leak. Just today (after a 70 MPH impact with a big deer) the puddle is big. When it rains, it pours, right? There is no white smoke coming from the exhaust. Any help is appreciated.

You sure its coolant and not normal condensation?

I thought that for awhile...but today, it is clearly green coolant.

I don't understand how you are not getting white smoke out the tale pipe..... Are you sure it's not leaking out and onto the exterior of the exhaust system?
Only 2 ways coolant gets inside an exhaust system....head gasket or crack....

I have never, in my 25yrs of being a mechanic, seen green coolant come out of the exhaust as anything other than steam.

Do a full compression/leakdown test, that would be my first step.

It's not coming out when the engine is running. Only when it is sitting. I agree...I've been doing this since for a long time (ten years professionally 80s-90s) and have never seen an engine dump coolant from the exhaust without other issues.

I suspect it's leaking into the exhaust and getting in there because you have a hole in your exhaust.

Yeah...it's coming out of the joint between the Cat and the exhaust manifold, which is irrelevant. The leak in the driveway is not the issue. The introduction of coolant into the exhaust at all, is the issue.

Sounds like a leaking heater hose connection, dripping onto the exhaust and running down to the point where it drips onto the drive/floor.

I understand that, what I'm saying is you may have a bad heater core connection. Which is leaking