Interesting thread!

My Mercury Marquis also developed a leak during the cold weather at the water pump/lower radiator hose junction! I tightened the clamp and the problem went away. Perhaps it has something to do with aluminum's high rate of thermal expansion (or contraction), but you people also report it happens at the plastic radiator necks.

This phenomenon makes a case for the old-style spring clamps that people remove in favor for screw clamps. There are some mechanics that actually favor spring clamps for cooling systems. For one, it prevents over-tightening the joint. And now we know that it can compensate for thermal shrinkage/expansion.

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95 E320 Cabriolet, 159K