Hi all!

I never really took much notice about the oil pressure reading upon start-up until recently. I know the greatest stress on an engine is on start-up when it is less lubricated, and I was wondering after a long or over night sitting, how soon or how fast should the oil pressure needle jump from 0 to 3? My 190E first goes in between 0 and 1 and then jumps to 3 within 2-4 sconds. What is the normal time it should move up to 3? Is it immediate upon start-up? My needle has a few seconds pause before it does. Thanks.

The oil pressure needle on my 420SEL always goes right to 3 on start up and stays there for a few minutes until it settles at idle. The only time I have had a delay is right after I change the oil. Even then it is only like 3 seconds before the pressure guage goes up to 3.



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Jason Priest
1986 420SEL

My gauage always goes to 3 the instant I start the vehice, and stay at 2 while idling.
Although mine never goes to 1, is oil pressure at 1 is a bad thing? How about someone shed some light on this subject?

95 R129
98 ML320

As long as the gauge reads at least .5 Mercedes says that is enough for a hot engine at idle. Each number is equal to 15lbs of oil pressure. Hope that helps. Most common failure is the sending unit!

Oil Pressure at startup is always higher than after warmup. The important parameter would be oil pressure after thorough warmup. If it is low at that time(below .5 Bar) would be worrisome.

Good luck,

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Larry Bible
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

Larry,
If it is below .5, that is worrisome....why does the gauge go up to 3? Isn't that the design criteria that it should read around the 3 mark when the engine is warmed up? My 420 SEL reads 2.5 always---should I worry? Heard alot of discussions on the the infamous oil pressure gauge. Would appreciate your comments.
sincerely,
Mike

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Michael Jay
1989 420 SEL

Lucy,

Does the oil pressure not come up to 3 when the engine speeds up? How low does it go when warmed up thoroughly and idling?

Good luck,

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Larry Bible
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

The gauge will peg 3 bar just after startup and will remain there until the engine warms up and the oil thins out some. 1.5 bar is correct pressure at idle at normal operating temp. Some of the larger engines such as the M-100 (6.3, 6.9) and the M-120 (V-12) will idle with the needle around 1 bar or 15psi when warm and at idle. It's just characteristic of the big engines. As long as oil pressure rises immediately upon acceleration, you have nothing to worry about. Funny this thread came up, as I had a '75 450SL in the shop the other day with 283,000 miles on it and when I was on the freeway on the test drive, the oil pressure gauge didn't even peg full pressure at 70mph. I'd say the mill was just a little worn :)

By the way, you guys with 380s, 420s and 560s, I would strongly recommend "priming" the engine after an oil change. To do this, look on the driver's side inner fender well for a black box (the ICU) which will have a plug with a green wire connected to it. Pull the plug and crank the engine over for about 15 seconds then re-connect the plug and fire it up. This will get the oil pressure built up to avoid a "dry" start.


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Rgds,
Aaron Greenberg
MB technician
Mercedes-Benz of Cincinnati
'67 250SE Cabriolet
'77 450SL
'80 300SD
'85 380SE
'86 420SEL
'89 420SEL
'93 300E 2.8
'74 Jensen Interceptor Mk.III
'81 DeLorean DMC12
'84 BMW 745i Turbo

[This message has been edited by Aaron (edited 11-05-2000).]

Can I "prime" my 240D oil system after an oil change? I just noticed that the gauge took several seconds to move off zero after changing oil. With spin-on filters, I always fill 'em up before spinning on. But there seems to be no way to do that on my '79 240D (616 engine). Thanks.
TedG
'79 240 Wiesel automatic
'95 Olds Gutless Cruiser
'73 Citroen SM 3.0 5-speed