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useful pic here albeit 4AGE which i grew up with

there is a bypass from 'out1' to the back of the water pump on the other side of the thermostat. this is a good example of the reverse flow. the cooling system in the corollas i had an my ta22 were amazing, got up to heat quickly, and, worked effectively.

That's a good pic and it clearly shows the flow of coolant around the engine when the thermostat is closed and the bypass is fully open. That's what needs to be achieved when fitting the mod to the lower hose. Even though the engine might not have a 2 stage thermostat there is still some form of bypass designed into the engine.

The Toyota 3F (re-engineered Chevrolet Blue Flame 6) had a bypass thermostat. Take them out and the engine doesn't warm up evenly. It doesn't overheat without it though. I think the 2H (diesel) has a similar setup.

The thermostat in many cases also acts as a restriction in the system so that the water pump can pressurise the block (in addition to the static cooling system pressure) to avoid localised boiling.
Some race engines run a coolant restrictor plate instead of a thermostat, which allows you to adjust the system flow/pressure characteristics.
So maybe the "too much flow" issue is really not enough pressure... Average engine temp may be lower but that steam pocket next to the exhaust port isn't doing you much good.

Yes, Agree with all of the above.

I recently replaced the LIM gaskets, pulled the old thermostat out and found it to be a 195°F unit so clearly it was faulty and allowing the engine to run to cold.

Now running a 180°C thermostat and temps seem to be holding nice and stable with the standard WP pulley fitted.

immortality wrote:Now running a 180°C thermostat

I hope that is a typo
It would be interesting to see the pump curves for those two different impellers (cast vs pressed). Did they run a different pulley ratio on the older style pump i wonder? The cast definitely looks like a more efficient unit.

Nope, pulleys never changed diameter from VN all the way to VY

charlay86 wrote:

immortality wrote:Now running a 180°C thermostat

I hope that is a typo
It would be interesting to see the pump curves for those two different impellers (cast vs pressed). Did they run a different pulley ratio on the older style pump i wonder? The cast definitely looks like a more efficient unit.

LOL, yes that should have been °F

Apparently GM changed back to a cast impeller pump for the last of the 3800 V6 engines in the US.