advisual

Temperatures were getting upwards of 230 or 240. Boiling reservoir going into cooling mode etc. - Overheating. Now it tops out at 181. get home cool as the other side of he pillow.

advisual

I just ordered another AC Delco thermostat. Going to give it one more try adding the OEM thermostat back in.

donbrew

Is the fan working? Is the t-stat 180F?

There have been some instances of parts books calling for 190F; they are WRONG.

advisual

Yes, comes on at 217

donbrew

Did you replace the pressure cap?

advisual

Yes, I have. But remember it is no longer overheating now that the thermostat is removed actually runs too cold I think.

Oldblue

Yes to cold , install the ACDelco thermostat and drain out all the water and pour in fresh 50/50 premixed Dexcool.

donbrew

There is no good explanation for the t-stat having anything to do with overheating, except for failing in a closed position.

My thinking is that if the pressure cap was bad that would allow the coolant to boil due to lower pressure. And that would allow the transfer of coolant to the jar.

When the engine cools down does coolant flow back to the system?

There are gas analysis kits available to check for blown head gaskets. Coolant should be blowing out even at 181F, if the gasket was leaking, that is where the excess pressure comes from.

You can test a t-stat with a thermometer and a pan of water on the stove.

advisual

So firemangeorge it finally threw the P0128 this morning. But it is driving beutifully. Does the fact that it does not overheat without the thermostat eliminate a blown head gasket?

firemangeorge

Not necessarily. Could be a very tiny leak/hole in the head gasket. But before you jump off in that direction.
Have you tried testing the last thermostat that was installed ? Since you have it out.
Put it in a pot of water on the stove and slowly heat it up. Have a cooking thermometer in the water to check the temp. Then see a what temp the thermostat opens(or if it does).