If my heat gauge is reading all the way hot but motor and coolant is only warm to the touch and no smoking or boiling over would it be the thermostat?
Probably Not. The heat gauge uses a ECT Sensor to indicate the engine coolant temperature. Sometimes if there is an air pocket the sending unit will read hot until the cooling system is properly bled. Once the system is properly bled you can use an infrared hand held temperature gun to check the accuracy of the gauge.
The first thing I would check would be the coolant level. Also confirm the temperature gauge sending unit wire is connected. If it has become disconnected it will read full hot all the time with Key in ON position.
If you just worked on it and are now having the issue, check around the area you were working to make sure you didn’t accidentally leave a wire disconnected.
You can check the the sensor by removing it and using checking the resistance ohms.
|Application||Resistance (Min-Max) Ohms||Temp ºF (ºC)|
|EX||15000 – 20000||-4ºF (-20ºC)|
|5000 – 7000||32ºF (0ºC)|
|2000 – 4000||68ºF (20ºC)|
|900 – 1200||104ºF (40ºC)|
|300 – 400||176ºF (80ºC)|
|100 – 300||248ºF (115ºC)|
Engine Coolant Temperature Sensor Location
Cooling System Bleed
For best protection, use Honda All Season Antifreeze/Coolant Type 2. This does not require dilution.
Ensure relay box lid is shut when pouring engine coolant to avoid damage to electrical components.
- Set heater temperature lever to maximum heat.
- Wait until radiator is cool, then remove radiator cap.
- Remove engine block drain plug adjacent to oil filter, then drain coolant into a suitable container.
- Allow all coolant to drain, then close all drain plugs and tighten securely.
- Remove, drain and reinstall coolant reservoir. Fill reservoir to MAX mark with coolant mixture.
- Loosen air bleed bolt in water outlet or water crossover, then fill radiator to bottom of filler neck with coolant mixture.
- Tighten bleed bolt to specifications as soon as coolant starts to run out in a steady stream without bubbles.
- With radiator cap off, start engine and allow cooling fan to cycle twice.
- If required, add more coolant mixture to keep coolant level at bottom of filler neck.
- Install radiator cap and inspect cooling system for leaks.