I have had the dreaded cold heater for some time now and looking through the posts I concluded it must be an air lock. This is after all the water pipe checks from where it starts coming out of the block through the exhaust heat exchanger, heater metrix and return pipes all flushed and free flowing, I filled several time as per Nissan's instructions including venting the high level pipes going in and out of the exhaust exchanger which at this point had good pressure but still cold air, obviously not enough pressure to push the air lock out and down the return pipe th the block 🤬🤬🤬.. What was needed was more flow... Another inline pump 🤔🤔🤔🤔 Brainwave... I connected one of those drill pumps between the heater out pipe and the return pipe to suck the airlock out and with the engine running after a few minutes bingo hot water running through the pump, I stopped the engine and pump reconnected the heater pipes and all good, piping hot heater 🥵🥵🥵😁
Hope this helps others.
![Image]()
Hope this helps others.
