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Don:
After reading forever about the evil plastic radiaor end caps, I recently went to an established long term independent rad shop. I asked the owner who has been in the business for a long time and is very knowledgable, about the longevity and the advisability about swapping my rad.
He said the material is a type of nylon which becomes brittle (changes composition)if overheated. He has seen steam erosion of the top nipple, that is, material has been washed away from the fitting by steam caused from overheating.
He says the plastic will last indefinitely if not overheated and he mentioned mid to high 200 deg Fahrenheit. He did say excessive tightening
could crack the hose nipple. He told me if it had never overheated and I keep the cooling system in shape i.e. hoses and coolant, I should never have to replace it.
My 740 has over 300,000 km and almost 11 years. a friend has a 85/740 with 460,000 kms he also has original rad with plastic ends.
I can see where bad motor mounts could fatigue the plastic, and furthermore the stressing of replacing these mounts by contorting the engine position could also cause cracking.
Some thoughts on the other side, by the way, I still have the original OEM
antifreeze but I add the corrosion inhibitor and waterpump lube at least once a year. Usually Prestone product. The voltage reading on the coolant remains low.
Sheldon
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