Maxxx

Want to reverse-flush my heater core this week . . . which hose running into the firewall is intake on the MDX, top or bottom?

Thank you.

Skirmich

The intended flush procedure per the manual requires to flush the block with the heater on max heat, It will drain the main heater core but not the rear passenger heater core in the center console.

If you want to literally plug a hose into the lines the line with the mechanic valve is usually the inlet.

Maxxx

Mechanic valve? What/where is that? Yeah, I was just planning to hook a garden hose up on low-pressure and flush out that core.

My heater core sounds like a fish-tank. I want to flush that first, no clue what is causing that sound but it can't be too good and I don't want any crud flowing back though the block. Will likely flush the block out next, but I am curious about what, if anything is in the core making it gurgle. Have only had this car 9mos.

Can't I just reverse flush the core using the intake and outtake lines going into and out of the firewall?

Hadn't considered that there was a rear passenger heater core though. I assumed the front/back shared the same core.

Carpayment4life

Caution, when removing either or both of the hoses, which connect to the firewall.
The male firewall part is quite soft and the female hose is usually hard, so the soft male end may get ruined.
Don't try to save the hoses, in order to reuse them. Cut them away from the firewall males.

Skirmich

The mechanical valve is seen from the engine bay on the heater lines, Its the one that opens up when you select the heater range of temperature and opens the valve so Antifreeze can move through the heater core.