Oil pressure diagnostic

[Kyiv]

Hello,


A while back I was searching for a lower wiring harness for my 1993 400E. My oil pressure needle was pinned to maximum oil pressure and would sporadically twitch nervously.

The lower wiring harness for my car is NLA, and after being unable to located the part new/used anywhere I had a mercedes/bmw shop with good reviews on Yelp take it out, rebuild it, and put it back in.


However, my oil pressure needle is still pins to level 3 as soon as the car started and remains there until I've been driving for a while, after which she starts twitching sporadically. My assumption is that since the lower wiring harness has been rebuilt, it must be the sensor itself. I also assume that the needle gets twitchy only after driving for a while because the engine compartment gets really warm, and electrical properties of the oil pressure sending unit change.

I also think that the twitchy needle shows correct pressure, as sometimes it'll stay - while twitching- for 2-3 seconds at 1.2 bar, which is the idle oil pressure I remember on 5w-50 after an hour or so of driving

Please let me know your thoughts on whether you think: the oil pressure sender or perhaps the lower wiring harness is culprit because it was not fixed properly?


Here is behavior of my oil pressure needle after 40+ minutes of driving:
https://www.youtube.com/watch?v=WwvZkPkzlqU&feature=youtu.be

 

[emerydc8]

That's very similar to what mine is doing, except mine stays at 3 during cruise and bounces below it at about the same rate as yours. When the engine is at a lower RPM it operates normally (1-2 bar). I can actually hear the gauge ticking when it pegs out.

I saw your prior post a while back and was wondering if it was my lower wiring harness causing this, but I think that has already been replaced. I've replaced oil pressure sensors on my 119s before, but I don't remember whether I've replaced the sensor on this car before. That's not to say that a replacement couldn't go bad too; but it hasn't gotten to the point of causing too much annoyance, as of yet. I'm leaning towards the sensor. When they fail, they seem to cause all kinds of different behavior. I will probably just order one and change it with the next oil change.

 

[gerryvz]

You have a bad oil pressure sending unit. It's a common part that is fairly easy to replace.

Here's a HOW-TO on how to do it: http://www.500eboard.com/forums/showthread.php?t=4287

Get a factory MB sender, or you can get a VDO aftermarket sender via places like AutohausAZ.com. Don't go with a cheap unit -- MB or VDO (the OEM for MB) only.

Cheers,
Gerry

 

[emerydc8]

http://www.autohausaz.com/pn/0065429417OE

 

[Kyiv]

Might as ell update this tread. New oil pressure sensor fixed my issue

 

[spaceman_west]

Where to get a new oil pressure sending unit?

 

[IslandMon]

Where to get a new oil pressure sending unit?

Option 1 - Your local dealer
Option 2 - The internet: mboemparts.com, getmercedesparts.com, etc

 

[gsxr]

If aftermarket, make sure it's Hella/VDO/Siemens only. Nothing else.

 

[Marcel107]

I did change the sensor a couple of month ago on my M103 in the 300 SL R107
The VDO No. is 360-081-052-003C > MB PartNo. A006 542 94 17
It was a PITA to replace the sensor