Cooling system pressure testing
In my case (recent Scorpion DOHC head gasket replacement) I pumped it up to about 25psi and waited for about 1/2 hour. Over that time it dropped to around 15 psi. The first run I found a leak at a hose clamp, tightened it, as it was loose, and that leak went away with no others apparent.
On the second pass, it did nearly the same thing with no external leaks apparent. This lead me to think the tester was faulty, as a leak-down test of each cylinder revealed no leaks. But in hindsight I think it was leaking a bit into the cylinders and I just couldn't see it.
In my case the coolant wasn't leaking out*, combustion/compression air was leaking in, causing air bubbles and resultant increasing funny temps as you describe. It takes very little air in the radiator to screw it up.
*Eventually I saw that while coolant wasn't leaking out much, when hot and parked after a run some coolant must've been leaking into the cylinders to cause the clean edges I saw on teardown.
And some rough running at startup, an eventually a coolant smell on startup as well. Only once did I notice any steam cloud from the exhaust and it was brief and right before I decided to change the head gasket.
If you can hang onto the coolant system pressure tester for another test, try this one (I just thought of it, should have done it myself): With a cold engine install the tester. Run engine and see how quickly the pressure comes up. If it's immediate, it would suggest a combustion air leak into the cooling system. If it's slow like one would expect from the coolant warming up, then that would be normal.
In my case (recent Scorpion DOHC head gasket replacement) I pumped it up to about 25psi and waited for about 1/2 hour. Over that time it dropped to around 15 psi. The first run I found a leak at a hose clamp, tightened it, as it was loose, and that leak went away with no others apparent.
On the second pass, it did nearly the same thing with no external leaks apparent. This lead me to think the tester was faulty, as a leak-down test of each cylinder revealed no leaks. But in hindsight I think it was leaking a bit into the cylinders and I just couldn't see it.
In my case the coolant wasn't leaking out*, combustion/compression air was leaking in, causing air bubbles and resultant increasing funny temps as you describe. It takes very little air in the radiator to screw it up.
*Eventually I saw that while coolant wasn't leaking out much, when hot and parked after a run some coolant must've been leaking into the cylinders to cause the clean edges I saw on teardown.
And some rough running at startup, an eventually a coolant smell on startup as well. Only once did I notice any steam cloud from the exhaust and it was brief and right before I decided to change the head gasket.
If you can hang onto the coolant system pressure tester for another test, try this one (I just thought of it, should have done it myself): With a cold engine install the tester. Run engine and see how quickly the pressure comes up. If it's immediate, it would suggest a combustion air leak into the cooling system. If it's slow like one would expect from the coolant warming up, then that would be normal.