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Thermal Cycling and Coolant Leaks:

I don't know how all of the other HUMMERS out there act, however I have had mine for 3 winters now and it always pees out a little coolant when the weather gets cool. It's the strangest thing none in the summer months and nothing when it gets real cold. Just the cool months. I also attempted to fix this problem and have had it in for service checks but I have found that nothing can be done. It is just like the Harley I have in the garage. It seems like all the big dogs like to mark their territory.

You're probably seeing the symptoms of thermal cycling, which is more pronounced in the colder months, and on larger equipment (with bigger hoses). The coolant heats up the rubber hoses, they expand and seal nicely, but compress the rubber to the point of a permanent set (i.e., the rubber cannot completely expand back to it's original shape). Then the trucks sits and cools (really cools in the winter) and the rubber contracts away from the clamp/connector. The cooling cycle tends to cause leaks at the couplings. You can tighten down the worm clamps, but this tends to damage the hoses...

A better solution is to use a clamp that expands and contracts with the hose and connector. Oetiker makes a proprietary clamp called a "Stepless Spring Clamp" that employs a tongue-in-groove design to maintain 360 degree contact with the sealing surface, and a spring loaded clamping screw that allows the clamp to "move" with the thermal expansions and contractions... In contrast, a conventional worm-type clamp has a pinched gap(s) under the screw plane which tends to worsen when the clamp is tightened to the extreme...

I recently replaced all (well most) of my coolant hoses and have planned to replace all my clamps with the "Stepless Spring Clamps" I have all the old hoses sitting around waiting to be measured, and hose ends counted so I can order the clamps. Note these clamps are more dimensionally critical than worm type clamps (i.e., you have to use the proper size). I too have little leaks, and have tried to only minimally tighten the hoses until I get off my butt and order the Oetiker clamps.

In a recent post someone suggested that these clamps be used on the Tranny hoses, which is the reason I originally investigated Oetiker clamps, but really small clamps were not available several years back when I queried them... Last I knew the smallest clamp was about a 1".


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