Quote Originally Posted by John_D
Is that an oil to water heat exchanger with the cable tie on it?
If so I'd put money on that being the culprit.
I've no idea what that part is or does...! Open to suggestions.

Flushed the rad, painfully slow with the gunk. Not 100& clean. Water not flowing freely thru the system. Below is the gunk that came out of it.

On a coffee break

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