Took my 94 camry 4 cylinder, to a mechanic cause it had a minor coolant leak, and the temp gauge was slightly rising with the car was in gear and at idle. Gave the mechanic $100 to tighten a screw on a hose clamp, and do a pressure test on the coolant system. Then, the pressure test was supossedly good. One week later I discovered the camry leaking more coolant than before, and the temp gauge rising even higher than before with the car in gear and at idle. But the first time the temp gauge would drop back to where it is supposed to be, and this time it would stay at the hotter position while driving down the road. So in fear I might over heat the camry, I took it to the Toyota dealer across the street this time around. They preform there diagnostic, and found I needed a new raditator. $400 and a new raditator later, I still have one of the original issues. I have no coolant leaks, but the camry temp gauge still rises to an uncomfortable position for me to be driving in fear it might over heat. I did however discover tonight that when I turn the cabin heat on the temp gauge drops and stays at the PERFECT level. Any help or advice would be greatly appericiated!

 

The loss of coolant could have been a leaking radiator. The upper tank on these radiators are plastic and prone to crack over time. The cracks at first are typically very small, then can often suddenly get much larger. If this was the case, changing the radiator was a good idea.

The first mechanic could have seen a slight amount of coolant from a crack in the upper radiator area and assumed it was a hose clamp.

The Toyota dealer should know about the cracking upper tanks and examine it.

Typically if the temp drops when the heater is on the engine coolant system is not working correctly. The heater being on, works like a small radiator (an old trick used on hot days for cars with marginal cooling systems).

Since you changed the radiator, the typically problem areas left are the thermostat, water pump, debris in the coolant system, radiator cooling fans. My "guess" is the dealer must have inspected the coolant and should have stated if it was dirty and the coolant system needed flushing out with water.

The water pump can fail at the blades moving the coolant, but this does not happen that often.

There are a couple of electric fans in back of the radiator. These fans turn on if the coolant temp rises above something like 209F, or when the AC compressor is on (AC compressor will cycle on and off when the AC system is on).

You can test the fans by running the AC and watching the fans. When the compressor turns on (engine lugs slightly) both fans should come on. Or if the engine idles long enough, the coolant will rise high enough to turn activate the switch that turns on the fans.

The fans only work when there is not enough airflow through the radiator, such as idle, stop and go traffic. If the fan system was not working correctly, the coolant temp would rise under these conditions.

There should be enough airflow at higher speeds, urban driving, hwy, etc and the fans would be off.

If the coolant temp on the gauge varies in all driving conditions and the fans work then check the thermostat. These can fail totally or in part resulting in the higher or lower coolant temps then normal.

If stated you the problems to each mechanic as described above surprised neither found the cause. The dealer may have "assumed" changing the radiator would solve the coolant temp problem. It would have taken them less then an hour to do all the other diagnostics and change the thermostat if this was the problem.

Not sure what mechanic to recommend, the dealer is more expensive but at least in part seems to know more then the first mechanic whom caught neither the leaking radiator or solved the coolant temp issue.