So I’ve been having a multitude of issues over the last couple of weeks.

My car has been overheating and I can’t figure it out for the life of me.

The Symptoms:

Temp Guage pegs to hot a couple seconds after starting the car. The radiator fans do not turn on at any point during driving. They will turn on if I turn on the A/C. The top radiator hose gets incredibly hot, while the bottom stays cool.

The Fixes:

I have replaced the thermostat, the coolant fan switch, the coolant temp sensor, the dashboard temp sensor, ran a completely new wire to the dash temp sensor (now I get no reading at all), checked all the fuses, replaced the water pump, and bled the air out of the system.

What am I missing? Any help would be appreciated.

 

I would verify that the temp gauge is working correctly.

 

thank you, I will do that. What do you think about the overheating or the fans not turning on?

 

I'm going to explain the switches and sensors on the cooling system.

Temp Switch A - Is on the thermostat housing and has a green and black wire and I think the plastic connector is green. This sensor closes when the coolant reaches 199 °F when the car is running and turns on both fans. The plug should point sidways (parallel to the ground).

Temp Switch B - Is near the water pump. Wire colors are wht/grn and black. This sensor closes when the coolant reaches 225 °F when the car is not running and turns on just the radiator fan for max of 10-20 minutes. This is to cool the engine and prevent heat soak.

Engine coolant temp sensor - Is also on the thermostat housing. It points up. It has two wires, red/wht and grn/blk. This sends the coolant temperature to the engine computer to adjust air/fuel ratio, etc.

Engine coolant sending unit. Also on the thermostat housing. Points up as well and next to the coolant temp sensor. It is a single wire sensor with a yel/grn. This sends the coolant temperature to just the gauge in your instrument cluster.

Which fan switch did you replace, and what sensor did you replace?
What wire and wire color did you modify?

 

I would check what temp the engine is running at. If the gauge is right I would check for symptoms of a blown
head gasket. The combustion in the cooling system may prevent the fan sensor from working.

 

I have replaced Temp Switch A, ECT Sensor, and ECS Sending Unit. I spliced the yellow/green wire from the back of the gauge cluster all the way to the ECS. I realize that it probably isn't getting any power, thus giving me no reading.

 

I have seen no signs or symptoms of a blown head gasket. Oil is clean, and so is the coolant. No smoke on startup or while running.

 

Did you verify that the coolant gauge is correct?

 

This is more for others reading this thread and for future issues you face. Most of the items you replaced were likely not necessary except maybe the thermostat. I usually recommend a Honda OEM thermostat, so it opens/closes at the proper temp. The problem with replacing parts is you risk installing a new part that doesn't work and can further complicate the diagnosis especially if you use aftermarket parts. Definitely keep the old parts as you might need to reinstall. I try to advise folks not to fire the parts cannon at a problem to save money and create more problems.

When this problem started, you said the top hose stayed cool and the gauge immediately was hot. It was unlikely the actual coolat temp rose immeditely, so you should have started on the engine coolant sending unit as it is the easiest & quickest to test. A blown head gasket could make the gauge jump to high. I'd hold off on that testing as the fix for a leaking head gasket is much more involved and expensive.

Try unplugging the wire at the sending unit and make sure the wire doesn't touch any metal nearby. Does the gauge stay at cold?
Touch the yel/grn wire to bare metal. Look at the temperature gauge and let us know if it moved to H. Do this quickly as keeping the temp pegged at H could damage the needle drive. An assitant woudl be useful to look at the gauge while you do this test. Let us know what you find.

 

sounds like you got separate issues, if temp gauge goes all way up after a few seconds starting car, engine is not overheating you got a gauge or wiring issue with that
fans not coming on totally different issue , when engine is warm no a/c on are you getting power and ground to fans?? ever test radiator cap ?