Rep Power: 0

I performed a coolant replacement on my 2020 Civic LX, 2.0 L in accordance with the service manual section SM6, pages 28 thru 30 and I had an issue.

I performed the procedure verbatim, but when I got to Engine Coolant – Air Bleed, section 5, step 2 the cooling fans did not come on. The coolant started to boil out of the expansion tank. This did stop after awhile. The temperature gauge got to about 75% of full scale. After about 5 minutes or so I stopped the car and allowed it to cool.

I checked the expansion tank, it was empty, so I filled it. Then I performed section 5, step 2. That is, I installed the cap loosely, started the car, and let it run, and this time the cooling fan came on twice.

About 2 hours later I checked the expansion tank and it was nearly empty. I filled it and looked for leaks under the car. Finding none I took the car for a drive and the temperature reached its normal level and remained there.

In the morning I checked the level in the expansion tank and it was down about an inch. I filled it, looked for leaks under the car and found none.

As I said, I followed the procedure, however, this doesn’t appear to be normal to me. Am I missing something?

Could I have done any damage to the engine?

 
Rep Power: 211

Any white smoke coming from the exhaust on cold starts in the morning or other times?

Did the bleed procedure call for the climate control heater temp to be on max with the fan either off or on? If so, did you check to see if it was blowing hot air through the vents?

If your car was a 5th, 6th or 7th gen those symptoms would point to a head gasket breach. I have no experience with Honda cars outside of the ranges I listed above.