Can someone tell me where and how to flush the rear heater core? I’m about to flush the front as it’s easy to access. Someone put tons of stop leak into the coolant and I’ve spent the last few days flushing the system. The front is pretty clean but after PAINFULLY bleeding this system I have no rear heat and only heat on the passenger side. There might be a tiny bit of air in the system but I think the heater cores are definitely clogged. I think the heater core is on the passenger rear? Do I have to remove the fender liner to access it?

 

You can follow the engine bay lines and flush front and rear at same time. Or for the rear you can disconnect the hoses mid-frame along right side and do the rear core directly.