@toyota4life I have been having this same issue with my 2003 Camry LE. I have replaced the thermostat twice, as well as the water pump also twice.

 

Hi Toyota for life, great details on the issue. Hopefully I can explain this in a way you can understand and I don't get too dyslexic on you while writing it.

If your temp sensors run the fans when unplugged, then I think you have found your open circuit, use a test light to ground and touch each one of the wires from connector side, do you get a light? Or does fan turn on?

When disconnected, stick your light on the prongs and other end to ground, when you touch the terminals, does your fan stop running?

If so I believe that wire will be your issue, as in open circuit or extremely high resistance, your test light will also show you if it's positive voltage, or open circuit. Then swap to positive side and touch your light to the terminals again and see if it stops the fans, or starts them when you have the sensor plugged in.

Access the wires always through the wiring connection side and try to get a needle or something similar so it does not damage
Anything inside like the actual wiring connection, or the rubber protection boots.

 

Pressure test the cooling system and the radiator cap. If the system doesn't hold pressure it will boil over.

 

Toyota4Life,

-- Since the fans come on with the temperature switch unplugged, I feel good about the wiring and relays. Also the temperature switches you are using appear to be fine. This leaves the following:

-- Please describe exactly what steps you took to purge air from the system. The Camry 2.2L is not easy to purge. Some people find that putting the front wheels on jack stands or ramps is the only way to get a proper purge. Also many people swear by a 'coolant filling funnel kit' like the kit places like Autozone sell.

-- Are you sure the thermostat is oriented in the correct direction? Two things must be oriented correctly: (1) the jiggle valve has to be as shown in the service manual (ak.a. "clocked correctly); and (2) the thermostat must not be installed backwards. If the jiggle valve is in the wrong position, then a proper purge is not possible. If you need elaboration, photos, et cetera, ask.

-- I agree that the radiator cap remains a candidate for being the problem here. If the radiator cap is not holding pressure, then the coolant will boil at a lower temperature, and the switch will never see the 199 degrees F or so needed to cause the fans to come on.

 

@1mzSaloonWagoon ,@corollacoaster ,and @Elle_Rav4
Thank you so much for the valuable information you all have provided me. Truly a blessing to have you wonderful folks provide your wisdom. I was able to figure out the problem! Before I get to the solution, allow me to reply to each of your responses as I went over them.

@1mzSaloonWagoon
Here's what I did as you suggested:

1. Test Light Check:
   • I used a test light to ground and touched each wire from the connector side. The fan didn’t turn on, and the light didn’t come on, ruling out a direct short to ground or any open circuit on the wires themselves.
2. Fan Test with Sensor Unplugged:
   • With the sensor unplugged, I touched the prongs with the test light (one end to ground), but the fans didn’t stop running, so no abnormality was found on the grounding side.
3. Positive Side Check:
   • I then swapped the test light to the positive side and touched the terminals again with the sensor plugged in. The fans didn't start or stop when probing the terminals, indicating no abnormality on the positive side or excessive resistance.

Performing this was very informative for me, I was able to rule out any issues with the wiring.

@corollacoaster ,and @Elle_Rav4

1. Wiring and Relays: I can confidently rule out any wiring or relay issues. I performed the test light checks and continuity tests as previously mentioned, and everything checked out fine.
2. Purging the Cooling System: To purge the system, what I did was, I put the car on ramps and started it from a cold start and then proceeded to take the radiator cap off. I added coolant until the system stopped taking more and topped off the reservoir. I also had the heater on full blast. After a few blurps from the radiator, I capped it and let it run to build pressure. However, the car still overheated, even after driving it around a bit to try and purge the system while driving. Unfortunately, that didn’t alleviate the overheating issue.
3. Thermostat Orientation: Regarding the thermostat, according to the Chilton manual, the jiggle valve is to be placed at the 12 o’clock position, which I ensured when installing it. There’s a notch on the top of the housing where the thermostat sits, and I aligned it correctly with the jiggle valve. So I don’t believe there’s any issue with the thermostat as far as I know.
4. Radiator Cap & Pressure: Here’s where I found the actual problem. During my first investigation as mentioned previously, while using a temperature gun, I noticed that the temperature was fine above the radiator but not below where the temperature sensor is seated. The hose connecting to the thermostat was hot but not hot enough to trigger the fans. After your advice on pressure testing, I dug deeper. When I pressure-tested the system, it was only reaching around 10-11 PSI, which I found out should be closer to 13-15 PSI after doing some research.
   The key detail here is that I had recently installed a new radiator, but it was leaking (brand new from the dealer). Unfortunately, the replacement is back-ordered for 1-2 weeks and that's quite the wait. Since the system wasn’t holding proper pressure, it wasn’t allowing the coolant to properly reach the temperature required to trigger the fans.
   So, I then replaced the new leaking radiator with the old one, which was still in good condition. During this process, I noticed that the upper radiator hose had a few small hairline crack with dried-up coolant residue. This hose had been replaced back in 2008 and had a cloth-sheathed design and grooves. I decided not to take any chances and replaced it with a new hose from Advance Auto.
   After replacing the old radiator and the hose, I re-purged the system, pressure-tested it, and this time it held at 14-15 PSI. Once the system was properly purged, the fans kicked in as needed, and the overheating issue was resolved!

TL;DR: The overheating issue stemmed from a new radiator that was leaking, which caused the system to lose pressure and prevent the coolant from reaching the required temperature to activate the fans. The pressure loss dropped the coolant temp from 200°F+ to 140-170°F at the lower radiator hose. I replaced the leaky new radiator with the old one and also found a cracked upper radiator hose (not original) with multiple hairline cracks from each grooves, which I replaced. I suspect that doing these tests caused the old upper radiator hose to crack from overheating and after nominal pressure was restored, the heat and pressure caused the cracks along given its age and brittleness. After fixing the hose, purging the system again, and achieving proper pressure (14-15 PSI), the fans now kick in as needed, and the overheating is resolved.

Thanks again for all the help! This was an excellent learning experience.

 

Reading this was very informative for me, as well. Thanks!

Performing this was very informative for me, I was able to rule out any issues with the wiring.

 

Beautiful. Well written, logically solved. I'd upvote twice if I could!

 

It's so really great to have a site like T-N where the sharing of information and experiences can come together to help other members fix an issue with their vehicles, in this particular article I learned the cooling system pressure might be effected by the radiator-cap, I really never gave much thought to my cap I change my radiator and related system parts every 10 years ( preventive maint ) in fact I'm going to be doing again very soon, a big thanks to all who participated in this posting.

 

Just in case it wasn’t mentioned, I strongly recommend getting an OEM cap. For whatever reason, the aftermarket caps are very prone to not working correctly right out of the box, or not working for very long. The OEM caps are well worth the extra $10 they cost. And I don’t say all that about a lot of parts.