When at idle, the oil pressure gauge reads about 2. As soon as you accelerate a little, it pegs out (hard), and stays that way. Looks like it is over-sensitive. Does this car have an electrical sender? Is this likely a bad sender or bad gauge? (I've never seen an electrical gauge get over-sensitive unless a shunt resistor becomes open). I have to repair the odometer, so I am hoping to fix the oil press gauge at the same time.
Question on the oil pressure sender on 85 300SD
Dec 09, 2003
4 Replies
At idle it should not read full pressure. I think your gauge is fine. Why is gauge sensitivity bad, anyway?
Normal to have 1.5 to 2.0 BAR at hot idle and 3.0 BAR above idle speed.
Jim,
Do you have an owner's manual? Have you read it? The behavior of your gauge as you describe it is exactally what it should do, if your engine is healthy. When I first drove our first 240D I, too, was surprised that MB would want the oil pressure gauge to work in this way. But they did!
Phil
'84 Euro 300D '85 300D
Well, I don't have the manual for this car, would like to see what it says. I didn't mention that the gauge ZERO is reading about "1" before the engine even starts! Is yours reading around "1" with the engine off/ electrical power on? I have also never seen another Mercedes instrument panel other than mine, but I am an instrument technician, so I tend to notice things like gauges whose zero calibration (error) is 1/3 of the total scale probably more than the average person. If Mercedes did indeed design this gauge system to work like this (zero of 1/3 of scale, and pegging hard 3+ whenever the engine is off-idle, then MBZ must have some village-idiot intern design this instrument system. But as long as it is showing that "3" when running off-idle, I won't worry about fixing it, I guess. Regards, Jim
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