My SD has begun to run over 100 deg C a couple times on the highway, reaching 115 or so for a minute or so. I suspect I am due for a flush and new coolant. I'm also hearing a squealing sound, making me suspect perhaps a water pump bearing or something. The belts look good, and there is no noticable leakage at idle. I did notice that the coolant appeared to be "flowing" (I hesitate to say bubbling, because I didn't see any bubbles, just some movement) inside the overflow tank where the hose from the radiator enters the tank.

I'm wondering if I would help matters by getting some citric acid and putting it into the overflow tank and letting it clean out the cooling system for a week or two until my tech can look at it.

Would leaving the flushing solution in for this long cause corrosion? Just wondering. Any thoughts appreciated. Thanks,

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Bob Roe
Lehigh Valley PA USA
1973 Olds 88, 1972 MB 280SE, 1978 Datsun 280Z, 1971 Ford T-Bird, 1972 Olds 88, 1983 Nissan Sentra, 1985 Sentra, 1973 230.6, 1990 Acura Integra, 1991 Volvo 940GLE wagon, 1983 300SD, 1984 300SD, 1995 Subaru Legacy L wagon, 2002 Mountaineer, 1991 300TE wagon, 2008 Murano, 2007 R320CDI 4Matic 52K, some Hyundai, 2008 BMW 535xi wagon, all gone... currently
2007 Honda Odyssey Touring, 2014 E350 4matic