Thanks. Coolant tank is new with the rebuild - should have mentioned.

 

@Matthew Markert In my case it blew out the overflow tube but initial only when the conditions were right hence the head shaped dent in the radiator cowl.

To check the lower intake gasket

From the front you will that big gap under the intake manifold.
Put a light shining in there (black light for the dye)
The slowly edge your camera in the fun part is the leak will be from the sides but you should see accumulation in the center

For the throttle body heater that is just annoying to check as the coolant tends to evaporate but you should still see a dye trace.

 

Discoloration on the hose, particularly the right one.

 

I think #thereifixedit

1) after a couple more runs, I found new coolant under the overflow drain hose. Wasn't there before (pic 1)


New coolant in the frame directly under the overflow tube after additional ridearounds

I moved the truck into the garage, turned off all the electrics and the lights (total silence) and this time I pumped the system up to 21psi instead of 19-20 like I did originally:

Eureka. Two leaks - one at the connection from the throttle body heater down into the engine - incompletely tightened clamp, coolant sits right on top of the engine and boils off. It was barely there, but it was there.

​​​​Second was the real one, but I finally heard "drip - drip"
Took a while, but the lower thermostat clamp (I had TWO on there, the original crappy pliers one and then a screw-tightening one) was leaking forward, so it was running down a line, and pooling under the radiator where I couldn't direct light into it. No drips on the floor! Lots of coolant though...I'm sure it came out when I drove.



Afterwards there is NO LONGER any pressure drop when retained at 21psi for 10 minutes.

And the crowd rejoiced
I do wonder about that first overflow stuff in the framee though...that makes me think there's an airbubble in the system. I'll have to get a vacu-pump to do it right, my method was a bit half assed (park on a sort of hill, turn the heat on, run for 15 mins, top off, drive around, do this twice for bleeding from the screw valve). I'm not ready to assume it's the HG or cylinders, this entire engine was rebuilt and there weren't any cracks before they put liners in. Fingers crossed and thanks for all the help friends! Think I just needed the fear it might be the engine to try harder on the lines, pushing an extra 2lbs did make a difference in part, perhaps only in whether I could hear the drip or not.

​​​​

 

Congrats!

Another way to test for an air pocket is to open the bleed screw when the engine is cold, stone cold. If coolant isn't all the way to the top, then you have found some air. Replace that air with coolant directly through the bleed hole and replace the screw. Usually checking again the next day, after some driving around, will prove or disprove that you've indeed removed all the air. It may take a few days of this to eliminate all the air.

 

Congrats. Great to solve a problem.

 

Turning the heat on doesn't do anything for burping air out of the system. Coolant flows through the heater coils constantly, regardless of your temperature setting.

 

Although you found the issue, another place to check is the upper left (drivers side) of radiator. Especially, if you had a shop install engine. There are two screws that hold the shroud, one on each upper corner, one screw is shorter than the other...so...if the screws get switch from one side to the other...the longer screw goes to deep and punctures the radiator. And it will leak enough to drive you crazy, but rarely show itself.

 

Nice tip!

I just checked, looks like that is fine.

In related news, I did a bleed, put the screw back on and....drum roll....it broke off in my hand!

Back to waiting. The gods do not give me favor today, as they giveth...they taketh away. I pay respects, and promise to feed them trailheads and whiskey laughter in the near future.

 

https://www.roversnorth.com/parts/pl...RoCl6cQAvD_BwE