found an answer to it

its burnt out stop leak. I had to remove the heater core too and took it to a place that used a water/air setup as a water hammer and purged out a lot of debris.

had to put in a new radiator as the stop leak had fused to the plastic of the radiator tank and was causing a slow erosion.

cleaned the whole system with shout/citric acid flush and got out lots of super fine gray sediment. hose flushed out everything again with hot connection from washing machine.

new japanese nissan branded pump, new radiator, new coolant (peak final charge truck coolant) - and its running again.

lesson learned - never underestimate the power of stop leak - it may stop a leak in the radiator but it may blow a hole in your wallet.

another learning was that aftermarket lower cost replacement water pumps for this engine are shipped with some sort of seal that is incompatible with even slight debris in the system, the replacements also warn to not use any silicated coolant. - Rubber seals maybe?


I have been recommended to install a coolant filter too and run it for a year or so to keep the system clean as there could be some debris still hiding somewhere. - I think its a good idea - the kit costs 70 dollars at napa

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)