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1990 Toyota Celica SF5E 2.2L engine overheating problem

1. All of the electronic sensors on the cooling system have been replaced
2. Both fans work
3. Radiator has been replaced
4. Radiator is an oversized brass radiator
5. Pressure cap is new and relieves at 13 psig
6. Cooling system when pressurized holds 15psig for 2 hours without pressure loss
7. I put pressure tester on radiator cold without pumping up and started engine
8. The pressure builds to 16psig in about ? hour and maintains 16psig
9. When the pressure builds up to 16 psig it relives the 13 psig radiator cap
10. Which makes the system loose coolant and overheat
11. WHY??????

It is not getting rid of the heat the engine is producing. I would suggest possibly a bad water pump or maybe a bad thermostat. It could also be a clogged radiator or engine sludge. (is this engine one of the ones known for sludgeing? Has the fluid been changed as recommended and only the recommended fluid used?

Replaced water pump last year, new brass radiator, no thermostst (I replaced the electronic temp controlers) Changed coolant every two years actually more because of the parts I’ve been replacing. Why does the pressure build up?

Have you tested for a leaking head gasket?

That would make the pressure build up.

Old Shade Tree States, "6. Cooling system when pressurized holds 15psig for 2 hours without pressure loss "

15 psig is nothing compared to the combustion chamber pressure. Combustion gases could be forced into the cooling system through a bad head gasket while still appearing to hold 15 psig pressure.

If it’s the head gasket, why does it stop and hold 16psig? I figuire after 2 hours it would build up more. I’m gonna get some leak dector and put it in the crank case to see if it is coming from a leaky cylinder and do a compression test over all 4 cylinders…Thanx OST

If you could do a cylinder leak down test, that would be better.