Greeting everyone, I am here for help before spent thousands on repairing the 2016 Honda Pilot w/ 70K. (I do sticking to the manufacturer’s recommended service schedule, oil change, fluid replace, etc)

1. No heat while the car in idle, but its working fine while car is in accelerating/driving (cold air while the car stop such as at the traffic light).
2. Fan and blend door are working.
3. Engine temperature looks fine from the dash board, no over heat issue. It takes about 10-15 mins for engine to heat up to the normal working temperature (middle range).
4. Firestone Complete Auto Care did back flush the heater core, replaced the coolant and checked leakage. They suspicion bad heater core or thermostat, and suggested me take it to the dealer.
5. Honda dealer and asked to replace the heater core for $2000 after cost of $200 diagnosis.
6. After all the research and YouTube video, and hope for the best to save on cost of replacing the heater core. I tried to do the radiator air bleed myself with the Coolant Funnel Kit. But the problem is, it keep getting small bubble after more than hour, the radiator fan did turn on a few time as I held the engine at 1.5K-2K RPM, getting good amount of heat as well. (Here is the photo, and it doesn’t look like anything from the YouTube. It’s like boiling but the temperature is about 170F read from infrared thermometer while the outdoor is 30F.)
7. Both coolant intake and outtake hose about the same temperature.
8. No thick white smoke billowing from the exhaust, but a pool of liquid on the floor under it, no smell, water likely.
9. Auto shop filled up the coolant in between Max & Min level about 6 weeks ago, it dropped close to the Min level in reservoir tank.
10. I tried to check the Heater Control Valve, but could’t find it on the 2016 Pilot. There is a photo of location from 2007 pilot on the web, but the 2016 looks like has different layout.

So, what do you think? The cost of repairing Heater Core or Head Gasket would up to $2000, and I hope that would not be my case. Thank you so much everyone.

• Blown Head Gasket
• Thermostat
• Heater core
• Heater Valve
• Leakage in the coolant system

 

Do a compression test, super easy and cheap

 

The engine should heat up more quickly, even if you start it and don’t push the gas, even if it’s cold outside, you should see it go to the middle of the gauge after no more than about 5-7 minutes.
Heater cores don’t usually go bad, it’s not typical, unless there is a leak, but then you would be losing a lot of fluid and possibly see it inside the car.
Also, after changing the coolant/antifreeze if topped off, it’s normal to have to add a little more fluid after using the car, because the fluid has to circulate around and fill all the cavities from when it was drained, and the first fill up of fluid won’t completely fill it to capacity.
I’m thinking it’s a thermostat stuck open so your cooling system is constantly working. And when you idle the car, it starts to cool down(but maybe not register it on the gauge).
Changing the thermostat is a lot easier and cheaper than changing the heater core. If there is a leak in the cooling system then you’ll have to continually be adding fluid every so often, not just once.
Let us know what you decide to do.

 

I was kinda thinking the same thing too with the thermostat being stuck open.. also the jiggle pin might be in the wrong position too but not sure if that would make much difference creating bubbles by having trapped air in the system.