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Thread: 94 E500 oil pressure question

  1. #1
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    94 E500 oil pressure question

    Hi all, I am new to this group. I am a Mercedes enthusiast with several Mercedes from a 300D-T to a 300SEL 6.3, but am new to the 500E/E500. I just looked at a for sale 94 E500, 101k miles, all records, and have two concerns:

    Oil pressure at hot idle dips to below 1 bar, and rises to 3 bar only around 1900 rpm. No unusual noises from motor. Motor has synthetic oil, 10/30, several years old, nearly full on dipstick but def needs changing. My other Mercedes dip at most to 1.5 bar and hit 3 by 1200rpm or so, so this is concerning to me.

    SLS reservoir level is at least an inch below the minimum level. No obvious leaks from the back of the car. Accumulators have been replaced and ride seems fine - not too harsh.

    Thank you for any thoughts. I would like to buy the car, and in particular given the 6.3, am accustomed to spending money to keep the car in top shape (some would say obsessive), but these two issues concern me. Thanks again.

    Andrew

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  3. #2
    E500E Guru Jlaa's Avatar
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    Re: 94 E500 oil pressure question

    The car should have 3 bars of oil pressure just off idle --- 1900 rpm is too late. It is very possible, though, that either:

    1) The oil pressure sender is faulty
    2) The lower wiring harness, which is made of biodegradable wiring, has degraded, and needs to be replaced
    3) The oil pressure gauge itself is faulty

    I experienced all three faults. You may start by asking if they have ever replaced #1 and #2, which is a bit more common ....
    ---
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    Re: 94 E500 oil pressure question

    Thank you - I know one wiring harness has been replaced - sounds like there are two? On my 95 E320 I just had to replace one. Thanks for any thoughts.

    Andrew

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    E500E Guru Jlaa's Avatar
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    Re: 94 E500 oil pressure question

    There are two - an upper and a lower harness. Both go bad.
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    Re: 94 E500 oil pressure question

    Andrew,

    First, Welcome to the Board!

    You didn’t mention your locatition but if you are really interested in this car or another one later on you should try to get a “Pre-Purchase Inspection” (PPI) by an E500E savy Indy Tech. That way hopefully you won’t be blindsided with a huge bill right at the start of your ownership. BUT there are no guarantees that a PPI will find everything either. Knowing your location someone here can at least send you to a competent tech.

    I can’t recall one case of really bad oil pressure in an M119 engine. These engines are pretty bulletproof in that regard.
    As far as the low oil pressure reading, this is a common complaint that usually ends up a faulty part as Jlaa stated above.

    You can also install a mechanical oil gauge on the engine but I will have to defer that to another member to tell you where to mount it.

    The current Owner is using synthetic oil which is the best for engine preservation so I would not be concerned about the age of the oil. I’m not a big fan of 10/30 oil in these engines either but I’m in SoCal and my car has had 20/50 it’s whole life and consumes no oil between 5,000 mile changes. I see no reason to go lighter. Your location may dictate lower viscosity oil.

    Anyway Andrew, Welcome Again I hope you can make the purchase and stick around.
    Terry

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  9. #6
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    Re: 94 E500 oil pressure question

    The lower engine wiring harness is questionable if it hasn't been done. Also, faulty gauge sensors happen without cause, and sometimes the lower harnesses shorting may possibly take them out. Look carefully for your gauge reading 3 bar with key on and engine off, with the pressure reading falling after the engine is started. That is usually a faulty sensor. Unless you are in a cool climate and/or in winter, 30 weight oil is too thin. Even with 50 weight oil, in very hot weather especially just after hard/ autobahn style driving, mountain driving, etc. the oil pressure can drop below a bar with the engine at idle in gear. I’ve been working on the M119 engines since they were introduced, and I have yet to see one suffering from genuinely low oil pressure, even after 300K+ miles.
    Putting the fun in dysfunction...

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  11. #7
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    Re: 94 E500 oil pressure question

    Low oil pressure indicated on the gauge is likely 2 issues: first, the sending unit is likely original, and they are known to read lower than actual when 20+ years old. A new OE/OEM Hella or VDO sender should help give more accurate readings. Second, 10W-30 oil is slightly thinner than MB recommends for warm climates (over ~80F). xW-40 or xW-50 is what was recommended in the early 1990's. Regardless, I would not be concerned about this if there is no indication of abnormal oil consumption. Search the forum for more information on both issues. The SLS fluid level low could be a leak from the tandem pump shaft seal, look for any fluid leaks on or around the AC compressor, which could be either SLS fluid or PS fluid (since the tandem pump is located directly above the compressor). None of these items are a dealbreaker for purchase, assuming the price is reasonable.

    Same question was also posted here: https://www.500eboard.com/forums/showthread.php?t=13169

    Dave M.
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    Re: 94 E500 oil pressure question

    Thanks, all. I am in San Francisco. I usually run my cars (except the 300D) with Castrol GTX 20/50, so I was planning to change to that. The car otherwise checks out pretty well. Is there a recommended source for the lower wiring harness? I assume this is fairly pricey.

    Thanks again for the welcome and advice.

    Andrew

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  15. #9
    E500E Guru Jlaa's Avatar
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    Re: 94 E500 oil pressure question

    Quote Originally Posted by Ab150 View Post
    Thanks, all. I am in San Francisco. I usually run my cars (except the 300D) with Castrol GTX 20/50, so I was planning to change to that. The car otherwise checks out pretty well. Is there a recommended source for the lower wiring harness? I assume this is fairly pricey.

    Thanks again for the welcome and advice.

    Andrew
    ohhhhhh..... welcome! Where in SF are you? I am on the west side.
    I got the lower harness from Naperville MB - mboemparts.com - this was maybe 2 yrs ago I think - the cost I remember to be surprisingly reasonable, like around 200 clams or less. If MB is NLA on these, you can contact Jono on this board who builds new lower harnesses at better-than-OEM-spec.

    The upper harness is easy to replace - I did it in my garage, working slowly, in a few hours. The lower one is doable with a lift but more challenging. If you have a lift in SF then I salute you (I certainly do not) but Jimmy Prountzos at Junipero Serra Porsche MB is just a few minutes away in neighboring Daly City who can put it in for you as well (do the oil press sender at the same time)
    ---
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    Re: 94 E500 oil pressure question

    If the car has been running synthetic already, there's no need to switch back to dino oil. 20W-50 is fine in the Bay area, although IMO in that temperate climate a 10W-40 would be fine. There's no harm using the 20W-50 dino, but I personally wouldn't go beyond about 5kmi OCI's.

    Lower harness details are here, including a link to the recommended source (Naperville):
    https://www.500eboard.com/forums/wik...Wiring-Harness

    And, here is a link about Naperville's free shipping code, which has been extended through 2018 despite the thread title:
    https://www.500eboard.com/forums/showthread.php?t=9399

    Don't expect the lower harness to fix an issue with the gauge reading lower than actual. I still believe the most likely cause of that is an old / original sending unit. more info in this thread from 6 years ago:
    https://www.500eboard.com/forums/showthread.php?t=2248

    Jlaa, the lower harness is more clams now... about 50% more vs a few years ago. Price jumped up with the 2018 annual increases.


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  19. #11
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    Re: 94 E500 oil pressure question

    Hi all

    Thanks again for all of your comments. I just bought the car. Will post some photos once I have them. Will start with oil and filter change plus oil pressure sender, and go from there. Thanks again.

    Andrew

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