But It's Brand New

Marv's Corvette needed a water pump.

Because 80% of the work to change the water pump is the same as changing the Optispark® distributor on his LT4 engine, I cajoled him into changing that too.

The engine bay on a 4th generation Corvette is extremely tight.

You have to remove a lot of things just to gain access to things you have to remove to gain access to the thing you want to remove.  The worst item is getting the harmonic balancer out of the way of the distributor.  You can, at best, get two of the bolts but then have to rotate the engine 120˚ to gain access to the third.  And even with it "removed" it's trapped between the frame and the stub of the crankshaft.

It's a slog, but straight forward.

Because C4's run hot normally, Marv bought a new thermostat thinking a 180˚ stat would help out in traffic over the stock 195˚ one.  He'd previously put in an all aluminum BeCool radiator with two extra cores over stock.

Everything was going fine until we were doing the coolant air purge stage.

What you do is idle the car, let it get hot, and once the temps are around 200˚ open a little cock on the thermostat neck to vent air that's trapped in the block out.

Normally you get spurts of air and steam for a little while then, eventually, a stream of fluid.

We got air, then steam, then higher pressure steam... and the temperature kept climbing.  The manual says shut it off at 260˚ to prevent damage, we shut of at 242˚.

Let it cool down, check levels, add a gallon of fluid, start over.

Same thing.

There had been a clicking rattle on first start that went away, so we begin to worry the new water pump had shed its impeller.  For a part that requires so much work to install, it has a surprisingly easy to get to access plate to see the impeller chamber.

Impeller is fine.

Could it be the thermostat?

Out comes the pot of boiling water and we find out that the new thermostat is not retracting the lower valve.  We also find out the old thermostat was 180˚.

Putting the old stat back in cured the problem and we got a fairly steady 197˚ even sitting in the stop-and-go cruise route around the bars on South Howard Ave.

Huzzah!

PS: The clicking rattle turned out to be the serpentine belt shedding a rib's worth of width.