Just swapped the gauge cluster on my '77 300D that is on the LH side which includes oil pressure, fuel level, and temperature. The donor guage cluster was from a late '70s Euro 240D, I believe, as it reads in Celsius and bar. Anyways, the oil pressure gauge snaps to 3 bar on startup, which is normal, but stays there even at idle and when the engine is turned off. It does not respond to variations in engine speed, including idle. A few moments after the engine is turned off, the guage will snap down to 1 bar, and continue to decline to zero pressure within 1-2 seconds after that.

Why would the gauge exhibit this sticky behavior? The original gauge did not behave that way. I was thinking of lubricating the gear train from the bourdon tube to the needle pivot with (what, sperm oil?). Any thoughts here?

Gerry Reynolds
'77 300D
'95 C220