What is correct oil pressure 1985 300D turbo? - PeachParts Mercedes-Benz Forum

raslaje · #1 03-16-2007, 01:13 AM

My oil pressure reads 2 bar at an idle of 800 rpm, then goes to 3 bar when I put the car in drive and take off. I just changed the oil and perhaps I'm just being more attentive since this was the first oil change I did myself, but I'm thinking that it was 3 bar at idle before. I put in 8 quarts and the oil is right where it should be between the notches on the dip stick. What should the pressure read at idle? http://www.peachparts.com/shopforum/images/new_smilies/dizzy2.gif

bgkast · #2 03-16-2007, 01:20 AM

That is correct operation. The gauge usually is pegged at cold idle, then drops once the oil cooler thermostat opens up. It should always be pegged when at speed.

t walgamuth · #3 03-16-2007, 06:03 AM

also did you change viscosity of oil?

a thinner oil such as synthetic might show lower pressure at cold idle than a thicker dino oil.

tom w

bustedbenz · #4 03-16-2007, 08:55 AM

How many miles were on the old oil? New clean oil of any viscosity is going to be thinner (and therefore lower oil pressure at idle as it gets going) than used oil of the same description.

raslaje · #5 03-16-2007, 09:52 PM

First I want to thank everyone for answering this and other questions I posed. The odometer hasn't been working for about 2 years since it clocked 200k+.(I intend to try DieselGiant's odometer fix, sometime between fixing my driver's side window - large gear fell down and is laying in the door, 2x4 keeping window up - and installing a crank window on the passenger side so my passenger can operate the window if the car is not running). The previous oil change was last summer, not sure what type oil it was. Might not even have been diesel rated as it is just lately that I learned on this forum diesels use a different oil. But I didn't put very much mileage on as I have a rear end banging noise after driving 25 miles, not before, so car didn't get typical use. I brought the car to an indy last summer and he said the sway bar links were bad and fixed them. Didn't cure the banging problem. Sounds like something in the trunk like a toolbox popping up. In fact I cleaned out the trunk thinking that just might be the problem. Nope. After reviewing various threads on this forum went to an indy that was familiar with Benzs and told him to replace the center bearing and flex discs. Heck I've been driving the car for 7 years, wouldn't be a bad idea to replace them. He did. He didn't think they were bad. He was right, didn't fix problem. He said pick him up when it makes the noise. I did. We drove uphill downhill fast slow couldn't produce the noise. So now I'm going to ask him to change the diff oil and look 'for play' (not foreplay) in the half axles or anything with the CV joints.

obiwanrazzy · #6 03-16-2007, 10:48 PM

I preffer a rubber door stop to keep the drivers window up...

I also was wondering about the oil pressure reading. Glad to know I'm not about to blow my engine to bits. Thanks for the info!

t walgamuth · #7 03-17-2007, 06:14 AM

Quote:

Originally Posted by bustedbenz

How many miles were on the old oil? New clean oil of any viscosity is going to be thinner (and therefore lower oil pressure at idle as it gets going) than used oil of the same description.

although it is possible for the oil to get thicker i suppose,i would expect tired oil to be thinner in most cases, and cause lower oil pressure.

tom w

derherr65 · #8 03-17-2007, 10:11 AM

My oil pressure gauge acts as described, but at just off idle it buzzes. The needle is vibrating and hitting the 3bar post. Is this a problem? Is there a way to fix it?