My 1984 300SD typically runs between 90 and 100 deg, but often right at 100 deg C. I've seen the needle jump occasionally, and when it does, it drops perhaps 5 degrees. This makes me suspect a slightly intermittent electrical contact somewhere. My coolant level is fine, at least in the overflow reservoir. Should I be concerned? I'm not worried, at least not yet; this car has been very reliable. I just don't want to smoke the head or anything.

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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