Like radience91 post , this A4 has recently installed FWC and after 10 hours or so, running at 170-180 under normal cruising conditions, developed a severe overheat. We checked all hoses, the Holley t/stat, the coolant pump and the raw water circuit and all seemed ok but the overheat persisted. There was good raw water cooling stream out the exhaust but it went from stone cold to 225 and boiling in 3-4 minutes under load.
FUrther investigation of the heat exchanger[vertical type] and the lower hose coolant return line found them blocked with a scale type debris that lodged in the lower section of the heat exchanger and the return hose and fittings. It even blocked the return port of the coolant pump effectively stopping coolant flow back to the engine.
I have not seen this before with any A4, although FWC conversions are rare,does anyone know what causes this scale build up and what to do to prevent it in the future. FYI coolant was 50/50 antifreeze & water
Thanks
FUrther investigation of the heat exchanger[vertical type] and the lower hose coolant return line found them blocked with a scale type debris that lodged in the lower section of the heat exchanger and the return hose and fittings. It even blocked the return port of the coolant pump effectively stopping coolant flow back to the engine.
I have not seen this before with any A4, although FWC conversions are rare,does anyone know what causes this scale build up and what to do to prevent it in the future. FYI coolant was 50/50 antifreeze & water
Thanks
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