Maybe a good flushing is needed.I know these guys will start crap over this,but I flush with thermo out driving car a hour with 50/50 water,an vinegar. always works for me.With a aluminum head you will need it to cool down before draining and flushing with water hose.I've used it for years.Besure and have heat on to flush heater core.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt