Oil Guage Reading - PeachParts Mercedes-Benz Forum

git0 · #1 03-07-2004, 08:34 PM

Another Oil Pressure Guage Question

1992 300E - 150,000 miles

I have owned this one since 20,000 miles and change the oil every 3,000 miles without fail. Lately the guage will often drop to zero - but no loss of power and then later will jump back to almost three while driving and lower while at a stop light. I am really concerned with it dropping to zero. Does this reflect:

a. faulty oil pump
b. faulty guage
c. other suggestions.

By the way my inide is not real concerned with the car having the original timing chain. He suggests the tell tale sign to listen for is a rattling or slapping sound at start up in the morning - whichI do not have. He doesn't seem to push unecessary repairs.

Any assistance is appreciated. Thanks.

Ali Al-Chalabi · #2 03-07-2004, 08:52 PM

I would first start by verifying the accuracy of the gauge with a mechanical gauge.

Specs say that min acceptable pressure at idle is .7 bar, but it should be pegged when the engine is revved. A flat zero at idle is not acceptable.

ILUVMILS · #3 03-07-2004, 09:04 PM

An educated guess leads me to believe the oil pressure sender is the problem. I've replaced dozens of these compared to guages. Now, if the fuel guage and coolant temp guages are acting strange it's a different story.

Concerning the timing chain? It's true the M103 doesn't have the same issues that some other MB engines have with timing chains. I saw a 103 engine go 275,000 miles on the original chain. I replaced it when I did the valve guides. I checked for stretch and was amazed when it showed NONE! I replaced it anyway because I had the head off and it cost next to nothing for a new chain. Having said that, I've also seen a few 103's break chains at barely over 100K. If it was me, and I planned on keeping the car for a long time, I'd replace the chain. It'll cost you a couple hundred bucks but if it breaks it'll cost a couple thou'. Just my opinion.

Evan · #4 03-07-2004, 09:06 PM

I to had the same exact problem in my 1991 300E,, i had previously had an oil change 2000 miles before the problem had started. I simply replaced the oil filter because i had an extra one. That fixed the problem.. Not sure how an oil filter can get so clogged or dirty in 2000 miles considering that the service on my car has been religous,, but i guess its possible..

git0 · #5 03-07-2004, 10:15 PM

Thanks guys

I think I will take it to the indie. He has been good to me so I will give him the business - even if it is just a sender.

I am seriously leaning to replacing the timing chain. My daughter likes the car so in a couple years it will be hers. Body and leather still in great shape.

Thanks again.

samiam4 · #6 03-07-2004, 10:50 PM

Timing chains...

I was always under the impression that it was primary V8 mercedes that required the most service. Diesels are always measured and like all engines dependent on oil change frequency/service enviroment.
My M103 will probably get a valve job in a year or so 100-120,000 miles is the plan. I'll do a chain at the same time, it's $100 for the chain.

Michael

Robert W. Roe · #7 03-21-2004, 02:44 AM

Do let us know what the indie finds.

My 300TE oil pressure has been dropping to zero at idle for a while now.
I'd be more worried about it, but I've had no problems with power, no weird vibrations or tapping, just right down to the zero peg on the guage.
It just bothers me that my oil pressure guage won't warn me of impending engine demise.

Does anyone know if replacing the oil sender is a diy job?
Do I have to drain the oil?
The car is a 1991 300TE M103.
Thanks, Bob

Ali Al-Chalabi · #8 03-21-2004, 10:33 AM

The oil pressure sender is not a terribly difficult DIY job and is a fairly common failure item.

You could either change the oil pressure sender and see if it makes a difference or hook up a mechanical pressure gauge to the engine and see what reading it gives.

Robert W. Roe · #9 03-21-2004, 10:06 PM

Ali, thanks for the reply.
I'm wondering how hard it would be to swap the oil pressure sender?
I mean, if I remove it, should I be prepared to catch 6+ quarts of oil or just a few drips?
I usually have my indie do most of the work on my car, including oil changes, but if I can save $$$ by doing this myself I will definitely try.
I just want to know if I have to be prepared to do an oil change at the same time, or if it's easy to reach, and won't dump all of my engine oil.
Thanks, Bob

jbaj007 · #10 03-21-2004, 10:17 PM

I know on the 617 engine you lose at most, 1/2 pint. Can't speak for the 300TE but shouldn't be much different judging from the position of the oil filter housing point of attachment.

Robert W. Roe · #11 08-26-2004, 12:29 AM

I just had my oil pressure sender replaced in my 300TE.
Now the guage works!
I had been getting zero oil pressure at idle;now it's at 1 or 2 at idle

Tigger55b · #12 08-26-2004, 11:51 AM

Most definitely replace the sending unit. You will have to take the filter off and you will make a mess doing that if you dont put a drip pan under it. You will only lose the oil in the filter. The unit is behind the filter and spins off easily with a 17mm wrench.

LEADFOOT · #13 08-31-2004, 09:09 PM

Took my 300E to my mechanic today to check this low oil pressure problem out. I was hoping that it was the sender. Picked up car, mechanic says the oil pressure is reading between 8 psi at idle and 20 psi at 2500rpm with engine at operating temperature.

When the engine is cold the reading appear normal, if not high. (almost a 3 bar reading)

Looks like it is two problems he said. The first is the oil pump and the second is the lower seals. I will leave it with him next week for a few days while he reseals the lower end of the engine and replaces the oil pump.

Has anyone else had this problem and if so, what was the solution? Could there be anything else?

thanks

LEADFOOT · #14 09-28-2004, 11:12 AM

I had new bearings installed on the bottom end. I also installed a new oil pump. $$$$

Almost no change from before.

(ONLY when eng temp is cold, does the oil pressure gauge on the dash indicates what was described above as "normal" . My mechanic says he verified the oil pressure hence, sending unit is okay with a mechanical gauge and it is reading 8psi when idling at warm, but the dash still shows zero. When engine is hot and I rev the engine or drive hwy speeds the dash needle moves up only slightly.)

Next, the mechanic is suggesting to replace the timing chain tensioner, as it might be a source of internal oil pressure loss/leakage. I'm over my head here...

Is this engine 'done for'?

Anyone had similar experiences? What internal leaks could be causing low oil pressure readings? What will changing the timing chain tensioner accomplish?

thanks in advance for any advice...