I just replaced the thermostat on my 1987 300TDT diesel wagon. Now the temperature reading is consistently 6-7 degrees hotter than before. Any ideas why this is the case? Thanks.

My mechanic replaced the thermostat in my '85 and the same thing happened, more like ten C degrees higher, from 80C (before) to 90C (after). When I asked, he said that some variation between thermostats was normal and anyway, the car runs more efficiently at higher temps. Thermodynamically speaking, that is true, but I'm not sure how much applies to the real world.

In any case, the temperature rarely rises above 90C so I just got used to the new "normal."

Jeremy

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
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"Oh lord won't you buy me a Mercedes Benz."
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what was the reason you changed the tstat in the first place? perhaps it was not closing all the way, and thus was not allowing the car to fully come up to temp? another possibility is that plus the older cooling system has some scale or whatever cutting down it's efficiency and the new tstat is showing this to you.
still another possibility is that they installed the wrong stat in your car. you may have need of a 165 and they put in a 195...

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
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My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

My car leaked about 4 ounces of coolant, so I thought I might have a leak in the thermostat gasket. My mechanic examined the thermostat and said it wasn't closing properly when tested.