91 300e oil pressure gauge goes to 0 - Mercedes-Benz Forum
 
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#1 (permalink) Old 05-04-2009, 01:24 PM
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91 300e oil pressure gauge goes to 0

I found some similar threads but not sure if this issue is exact as others.

Last couple weeks the oil gauge has been dropping to 0 after a few minutes of running. Here is what happened this morning.

Start car, pressure to 1.5 and rpm is around 900.
Put in reverse , goes from 1.5 to 0
Back to park, goes back to 1.5, leave in park for couple minutes and goes to 0.
Turn car off, start again goes to 1.5 but immediately goes to 0.

RPM now around 700-800, give a little gas rpm at 1500 and pressure comes up to 1.5, let off and it drops to 0. Rpm up to 3000- pressure up to 2, let off gas and pressure drops to 0, but now engine struggle to idle, rpm around 400-500 and abs light comes on for 10 seconds. Idle gets back to normal and check engine light came on.

Drove around town , no issues. Temp around 80C. Car seems fine, but I think I am about to have some real issues, just don't want them to be on the highway.

Where to check first?
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#2 (permalink) Old 05-04-2009, 01:39 PM
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Tim,

Thanks for posting your question. Do yourself and the rest of us a favor by completing your profile. It's very helpful.

From your description of the problems, I'd suggest first taking the steps to check that your car is getting proper voltage. A fully charged battery should read 12+ volts with the car off. Running, you should read something more than 13.4 volts. Insufficient voltage would be an indicator of ABS/CEL lights coming on at random as well as a host of other odd grimlins. Low oil pressure readings may be part of that as well.

If the voltage checks out, then more than likely, your oil pressure sending unit is on the fritz. It is an easy part to remove and replace and not expensive. You'll find it mounted to the oil filter block, below the filter, near the firewall. It has a single wire lead. I can not recall any thread in the past few years where an oil pump failed.

Report back on what you find and good luck,

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#3 (permalink) Old 05-04-2009, 06:06 PM
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Thanks for quick reply, voltage 12.7, and 14.4 when running.

Any way of testing sending unit?
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#4 (permalink) Old 05-05-2009, 04:04 AM
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No way to test the unit that I've heard of. The replacement part is $32.95 from autohausaz.com

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#5 (permalink) Old 05-05-2009, 06:45 AM
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Before you buy the sending unit, you should check the condition of the wire which goes to the sending unit. That wire on my 94 E320 wagon was in rough shape and I was experiencing erratic oil pressure gauge readings and it was going to zero as well. The fact that your gauge moves at all tells you something.

Anyway, after splicing in some new wire and some shrink tubing, my oil pressure gauge reading was spot on again.

Steve
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#6 (permalink) Old 05-05-2009, 11:55 AM
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Yeah, these oil pressure sensors rarely fails, unless if your car was sitting for a long time and get clogged up with crud, why not you take the oil pressure sensor out and give it a little cleaning, that worked for my 300SD, i shot some brake cleaner into the the pin size hole of the sensor...

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#7 (permalink) Old 05-08-2009, 12:58 PM
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Cleaning did not help, wire looks ok. Ordering part.
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#8 (permalink) Old 05-15-2009, 01:37 PM
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Sending unit fixed the problem.
Thanks
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#9 (permalink) Old 09-29-2010, 03:41 PM
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Post Low pressure at hot idle

Under normal operation and temperature conditions the oil pressure rarely goes below 1 at idle. When hot sitting in traffic it will drop to zero but go up quickly with a few more RPMs. I suspect the sending unit.

Can someone please confirm the location of the oil pressure sending unit on the 119 engine? Is there a separate level sensor as well?

Link or part number would be great.

I just want to make sure I get the right part and am removing the right part as well.

PS:

I tried to look at the DIY manuals and could not find this documented

Cheers

Bruce Kennedy

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2006 MBZ E500 Wagon
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