High oil pressure at idle - PeachParts Mercedes-Benz Forum

muleears · #1 10-23-2010, 05:26 AM

New to me 83 SD. When warm oil pressure at idle is about 2.5 bar. This seems high to me, my other cars are under 2 at hot idle. Also the OP gauge rests at 0 with the car off but moves up to .5-1 bar with the key on but engine not running. Have I got a plugged oil gallery causing high idle pressure or a bad sending unit. I just got the car and have not changed the oil yet. It may be very dirty (or 90 weight for all I know). What do you all think?

layback40 · #2 10-23-2010, 06:58 AM

It sounds like it is an electronic gauge. There should be an adjustment on the back of the gauge. It needs to be set at 0 with ignition on & car not running.

Paulc66t · #3 10-23-2010, 07:48 AM

My 83 usually idles @ 3.0. Once in awhile if the oil is older(before change) and running hot it will drop to 2.5. It varies depending on viscosity and idle speed. The SD gauge is electronic.Not sure if you canadjust it.

W124 E300D · #4 10-23-2010, 08:09 AM

1/ check the sender, for starters it is easier to swap out if dodgy.

2/ The MB oil pressure gauge isn't actually calibrated in anything, but anything over tickover it should be at 3, hot or cold, new oil or old.

barry123400 · #5 10-23-2010, 10:29 AM

No harm just living with it either. The calibration could be the gauge or sender. If you can get a cheap sender to sub in as a trial from an auto wrecker I might try it. You just mentally extrapolate the pressure otherwise. Whatever is indicated just remove the .5-1.0 bar initial reading.

Jeremy5848 · #6 10-23-2010, 10:49 AM

The Mercedes oil pressure as indicated on the electric gauge is more of a "serving suggestion" than a real number. For example, my '87 300D Turbo (W124, OM603) reads about 1 bar lower than a mechanical VDO pressure gauge, which I installed in parallel with the electric gauge. As long as the electric gauge pins high at engine speeds above idle you are good to go. DO NOT make any assumptions ("plugged oil gallery") about the engine based on the electric oil pressure gauge.

BTW, the mechanical gauge on the W123 family of diesels is more likely to give a true reading.

Jeremy

muleears · #7 10-23-2010, 10:55 AM

Thanks for the rapid responses. I guess it's nothing to worry about. It does go to 3 immediately off idle.

Diesel911 · #8 10-23-2010, 12:55 PM

I also vote for the Sending Unit. But as the other member indicated; until you put a test Gauge on it you will not really know what it is pointing to.

Ya Mar · #9 10-23-2010, 02:09 PM

My w123 is almost always at 3, sometimes when idling it will drop down a little bit, but always comes back up when I start driving.

mach0415 · #10 10-23-2010, 03:01 PM

An 85 SD has an electronic gauge. If the gauge is out of calibration, then it should be at .5 - 1.0 bar if you unplug the sending unit - just a quick and easy way to check. I also would bet its the sender, though. On cold start my gauge is at 0 or below with the engine off. Cold idle is at 3 bar, and hot idle is at 2-2.5 bar. Anything above idle on these cars usually pegs the OP gauge to full sweep.