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1988 560SEL sold:
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Discussion Starter #1
Tweaking the wire restored the oil pressure gauge.
2 Bars when idling in P
1.5 Bars idle in D
3 most of the time when the foot is on gas pedal.

I believe these readings are normal. However, I do have a question: is it normal for the gauge needle to shoot up to 3 upon start and stay there until the engine warms up regardless of which gear I'm in?

BTW it's a 15W-40 oil
 

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Glad to hear that you could inexpensively fix your oil pressure indication problem by verifying the condition of the cable leading to the indicator gauge.

A reading between 1-2 bars is not at all unusual once the engine has warmed up. As you've mentioned, it will be slightly higher when the transmission is not engaged (P). The indicator gauge should, however, stay pegged whenever the car is not idling.

If you have recently replaced the oil pressure transmitter (attached to oil filter), you should troubleshoot the oil pressure problem ASAP. I do not want to cause FUD, but insufficient oil pressure may cause all sorts of nasty issues related to the timing chain and, more specifically, impair the chain tensioner's ability to function properly. I may have simply misinterpreted your definition of "3 most of the time", but some of the following steps are fairly easy to perform, and will give you additional peace of mind.

#1
If you have not recently replaced the oil transmitter, do the following:
1) Get a multimeter that gives you ohm readings and unplug the cable at the pressure transmitter
2) Connect multimeter's probes to the transmitter's prong and the engine (ground).
3) If ohm reading is < 0.10ohm, the transmitter is giving accurate readings. Otherwise, replace the transmitter

#2
Remove valve covers, and verify that oil supply lines on cam towers have no play. They should sit _firmly_. Replace the plastic pieces, if in doubt. Inexpensive insurance.

#3
If oil pressure is still subpar, and you are using a quality oil filter, it may be worth checking your oil pump. The oil pump filter can easily be replaced/cleaned, and while you are at it, you can also clean the oil pump itself. The pressure relief valve may become less effective due to dirty oil and start to "stick". Oil pan gasket & oil pump filter (pick-up filter) will be required to perform this service.

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The gauge needle should always jump to the 3rd bar and stay there until the engine warms up. The gear is not a factor influencing this behevior, as this has to do with the temperature of the oil and its viscosity characteristics under changing temperatures.
 

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Discussion Starter #4
Thanks, that clarified everything. The needle stays at 3 bar regardless of what gear I am in and what RPM I am at during the warmup period. Once the engine is fully warmed up, the gauge needle is at 3 Bar mark unless I am in idle or in a prolonged coast. It is good to know that the oil pressure sender functions (both the unit and the wire) are working, and even better to know that the oil pressure is where it should be. However, I will come back to this thread from time to time to review the items you've noted.
 

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1991 300 SE
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naomilla - 3/23/2005 11:29 PM

However, I will come back to this thread from time to time to review the items you've noted.
Just copy and paste the text to a Word document and burn it to a CD like I do – you don’t know how long the thread will be here and you’ll have quicker access for reference that way.
 
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