Hope to get to this this week.

Will remove heater control valve and identify which of the heater core tubes I should use to reverse flow.

then I'll put the garden hose to it to blow out any remaining antifreeze and sediment, if any.

After letting the plain water drain, I'll fill the core with a 10-minutes radiator flush chemical forced in by a garden sprayer. Probably this will be a solution of the chemical and hot water, according to bottle directions.

After letting it sit, I'll backwash again.

I imagine one could use a small pump, like the kind used to pump water off a swimming pool cover, to circulate thissolution contantly from a bucket through the core, letting it flow back into the bucket. Use some long length of common heater hose or old garden hose clamped to the the pipes of the heater core.

You could probably use this contraption likewise to flow through a solution containing your leak stopper ingredient, if you are so inclined.
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1989 740Ti 1986 240DL 1984 244GL