You may be able to find purpose-made coil cleaner for HVAC systems at your local Home Depot and use it on your radiator. I don't see why that wouldn't work. I have some but I don't think I tried it on my radiators. It seems to be just an extremely concentrated alkaline soap along the lines of the Castrol Purple stuff but much stronger.

Rick

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80 300SD (129k mi) 82 240D stick (193k mi)77 240D auto - stick to be (153k mi) 85 380SL (145k mi) 89 BMW 535i 82 Diesel Rabbit Pickup (374k mi) 91 Jetta IDI Diesel (155k mi) 81 VW Rabbit Convertible Diesel 70 Triumph Spitfire Mk III (63kmi)66 Triumph TR4a IRS (90k mi)67 Ford F-100 (??)

********Az has the Nissens for 195

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91 350SD
14 F150 Eco
19 Fusion Hybrid
11 GT500