A few suggestions:

Check that the coolant reservoir cap has a tube on the underside of the cap that dips into the coolant. If missing, it’ll cause the cooling system to suck in air when it cools.

Look closely at the radiator for leaks. If there are any, the system won’t be pressurized which lowers the boiling point of the coolant.

Take the radiator cap to an auto parts store that can test it to see if it’s holding the pressure it should. If it’s not, get a new OEM cap. Aftermarket caps are a crapshoot.

 

I have that tube, but the coolant reservoir leans a little to one side, so I'm wondering if the tube is actually dipping into the coolant or not.

 

Please do the other tests outlined in BMR's post:
- have your radiator cap pressure tested
- pressure test the radiator and inspect around its edges for any leaks or pink crusty residue indicating a leak

Tell us what you find from those tests.

 

98 2.2l if needed

 

The way you are describing the gage swings almost sounds too fast for it to be the coolant temp. Can you put an OBDI reader on and check the temp there to rule out a cluster/gage problem? You might check resistivity of your old and new temp sensors too.

 

I had a radiator replacement done. I can tell you if you start seeing Pink crust forming on your radiator, it's most likely on its way out. I was advised against using sealants to fix the radiator. I was told it could possibly damage the heater core.

Check out RockAuto. Order an OEM radiator, typically Denso. For the hoses, thermostat, coolant, radiator cap, etc, I ordered them from a local Toyota dealership. Their parts department website had a sale. The cost of these parts are very similar to aftermarket, and I don't recommend aftermarket parts if OEM is typically the same price. Not sure exactly what the cost may be for your car, but for my Venza, it was very similar in terms of pricing.

I commented on this thread, and a lot of users helped me in terms of fixing my coolant/radiator issue. It started on page 3 and ends on page 7, but if you want to read through all of the details on why using a sealer may not be a good idea, it should also be on page 3 as well bit towards the bottom.

Best of luck with the radiator situation

Thread link: Coolant system air pocket?! | Page 3 | Toyota Nation Forum

 

I don't have an OBDI reader. And I don't see any pink crust forming around the radiator at all.

 

I got the coolant system and the radiator cap pressure checked and both appeared to be functioning as they should.

 

If you don't mind me asking. I read through your original post and had a quick question. After you put in a new coolant temp sensor you gauge didn't work if you put the old sensor back does the gauge seem to be working again?

I don't know if that's the definite problem I'm just making a suggestion but I'm assuming something wrong with the sensor at this point or maybe the cluster itself. Maybe you got a bad sensor. Stick with OEM Denso.

If you got all the air bubbles out there shouldn't be any more problems at this point. Do make sure your thermostat is at the 12 o'clock position.

 

I finally figured it out. This camry has two sensors that are connected to the temperature gauge. I replaced the coolant sensor gauge but not the other. After further inspection, the connector was cracked and connecting on and off. After replacing it, everything works as it should. Thanks for all your help!

 

This camry has two sensors that are connected to the temperature gauge. I replaced the coolant sensor gauge but not the other. After further inspection, the connector was cracked and connecting on and off. After replacing it, everything works as it should.

Your 5SFE Camry has only one sensor (sender) connected to the instrument cluster's temperature gauge. This sensor (sender) should have a single yellow/green wire at the connector. The service manual calls this sensor the "Water Temp. Sender." A second coolant temperature sensor sends a signal to the engine computer. It has two wires at its connector: One green/black and one brown. See Strega315's post #4 at https://www.toyotanation.com/threads/what-scanner-tool-will-show-engine-temp.1729949/.

The connectors and wiring at the locations of these two sensors do tend to get beat up. Good job figuring this out.

 

There are a few h2o temp sensor in the 98 2.2l but for the cluster its only one. The one on the left is for cluster, green on right is for ECU usage. The testing procedure was in post #6 clearly shows the sensor and harness plug as single pin type.

 

Thanks guys. Yes, it was the one on the left. I'm still new to this. Thanks for all your help

 

The underhood plastic connectors on 27-year-old Toyotas are quite brittle, and tend to break when you try to remove them. Replacement plugs are available at most auto parts stores and at Amazon/Rockauto. Take a picture of the end of the plug and compare it to pictures online. They are all different shapes for different uses.