Hi, I am new to the forum. I have a 1991 350SDL that has suddenly developed a problem with the oil pressure. I have changed the oil and filter--Mystik 15w50 synthetic blend and a Wix filter. I also replaced the oil pressure sending unit. None of the above changed the problem. I know the full history of the car but won't go into detail now. It had a new engine installed by MB at 150,000 miles.

I had just returned from a 1700 mile trip, and the car performed flawlessly. The day after I returned, I was pulling into traffic and noticed the oil pressure dropping as I accelerated. I let up off the pedal and it crept back up. Pressed the gas and it dropped again. It seems to happen under load at slow speeds, and returns to normal once cruising speed is reached. Oddly, if I accelerate in reverse the pressure jumps up, Forward, it drops. I have removed the filler cap and verified that oil is flowing to the cam.

I am including a video link. This was shot while accelerating from a stop, engine at full operating temperature after a short freeway run, and on a sharp incline over a viaduct. If I let up and allow it to shift the pressure jumps back. The first few fluctuations in the video show it going through the gears; the last one I gunned the engine to see the effect.

https://www.youtube.com/watch?v=TD7XJ1l_plQ&feature=youtu.be

Any ideas?

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1991 350SDL
1974 VW Safaré Camper