94 Camry V6 now overheating instead...
 

Today, I replaced the coolant temperature gauge sensor that's been out of commission for about a week, and sure enough, it started reading true. The engine has been overheating for the last week and a half.

Driving around a bit, I noticed two things. First, it got up to about the 2/3 to 3/4 mark during the drive (bad), but did not reach above that (good). Second, it ran cooler at idle (about the half mark) than during acceleration and highway cruising, telling me that the coolant system is not circulating the coolant properly.

I have not heard any squeaky or grinding noises while driving, implying hopefully that the water pump is operating properly. The radiator has been leaking slowly from the top since I bought it a year ago, so I'm inclined to think it's a bad/clogged radiator. O'Reilly has one listed online for $114.

Any insights? Is there a definitive test I can do or get done to determine if it is in fact the radiator before I buy a new part?

What's the best way to make sure I haven't fried/warped my head gasket?

There is test for exhaust fumes infiltrating the cooling system. They insert a collector with the radiator cap removed. Then, a blue liquid is poured into the clear plastic collector. If it turns color, exhaust is burbling through the head gasket and into the coolant.

In thinking about the steps you've taken, I heard something years ago about completely removing a thermostat. It isn't good. The coolant transfers heat to the radiator best at a determined rate of low. Forcing Hoover Dam through isn't necessarily a good thing.

I'm getting old, so I myself don't trust the automotive technology my dad taught me in the '50s. Things have changed a lot. But, call a Toyota dealership and ask them if removing a thermostat would adversely affect a V-6 engine. And, what would the symptoms be? With no backpressure at all, you could be getting cavitation at the water pump. But ask someone who knows.

Well, I have a new thermostat in place, so the flow should be appropriate.

Today I popped the hood to gain insight and noticed that the sensor was not screwed in all the way. Threads were still showing about 1/4 to 1/2 inch. So I started racheting it further in, and as I was mentally noting that it was awfully hard to turn, it snapped off in my hand. I must have cross-threaded it. I plan to pull the radiator cap/sensor gauge housing off another car at the salvage yard in the morning to fix my idiotic mistake.

My muses at this point: if the sensor was not submerged enough, would it affect the reading? Maybe. I won't know anything until I replace the housing and gauge tomorrow. But it sure has been a fun mental puzzle that should have just been a simple repair. I'll keep you posted.

Temp sender sticking out a bit?
 

Bravozulu, does your temperature sender stick out a bit from the housing? About 1/4 inch of thread showing? I saw another V6 Camry engine this morning with it sticking out a bit, making me think perhaps that's the norm. (even though it would be an odd design...)

It's located at the base of the water-inlet housing (the neck with the radiator filler cap on top, on the belt side of the engine). I know it seems a minor thing, but it would be a big help if you could check really quickly for me. Thanks :)

I can't see it. My old eyes aren't the best. Listen, if it is brass the threads will more or less be self sealing. No need ram it to the hilt. The water is only pressurized to 1 atmosphere, so any leakage will just be a seep if it isn't firmly nested in the block..

As far as doing its job, the entire block heats up the same temperature, so the sender doesn't have to be swimming water.