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Old 08-30-2001, 03:52 PM
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Join Date: Aug 2001
Location: Florida
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400E no oil pressure at Idle

Afternoon guys

Let me bother you with another question about my 400E.
I changed the oil the other day and against my better judgment I took the advise of the book and installed 10w40. I live in fla and don't think it has the viscosity to build pressure. Also the auxilliary fans ar running at what sounds like half speed. Any help woud be greatly appreciated.
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Old 08-30-2001, 05:11 PM
Ali Al-Chalabi's Avatar
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Join Date: Nov 2000
Location: Knoxville, TN
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The aux fans have two speeds, low and high

Low switches on when the A/C pressure gets to a certain limit.

High is on when coolant temp hits 107C

Regardless of the fact that you are using 10w-40, there should still be good pressure at idle.
Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record
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Old 08-30-2001, 07:55 PM
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Thanks for the clarification about the fan speed..haven't seen 107 yet so I feel good about that.

Have good oil pressure until the engine gets hot then its very low at idle..I haven't had the automobile that long and I can't remember noticing anything different on my 260 but a friend of mine says it isn't right. When i accelerate the pressure pegs immediately and when I open the oil fill at idle the oil is flowing at a good rate. Maybe it is correct? I don't know. The owners manual says it is normal for the oil pressure to low after reaching operating temp. Thanks for the input.
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Old 08-30-2001, 08:16 PM
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Join Date: May 2000
Location: Soperton, Ga. USA
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At idle is the needle at .7 bar or higher? If it is then you are ok. I would not worry about the 10W40 wt until the next time you change it then just maybe go a little higher based on ambient conditions.
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Old 08-30-2001, 08:22 PM
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Join Date: Jun 2001
Location: California
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The best way to find out if you're okay is to temporarily install a mechanical gauge. That will tell you what the oil pressure is REALLY doing and help you diagnose whether you have problems with your sender or gauge. You can get a gauge anywhere (even Wal Mart) - pretty cheap.
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Old 08-30-2001, 08:49 PM
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Location: Omaha, NE
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My 400E has always ran a pressure of 0.5 bar at idle, in gear, in summer, with AC on. The manual tells us clearly that anything above 0.3 bar is acceptable, as long as the pressure comes up immediately with increased RPMs.

Not to start YET ANOTHER thread about synthetic oil, but since the switch to Mobil 1 15W50, idle oil pressure is always above 1.0 bar even in summer. I just think it makes sense for this engine, which tends to run on the hot side, to give it as much protection as possible . . .
'93 400E
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Old 08-31-2001, 10:13 AM
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Same hear Steve! My pressure is averaging well above 1 since I switched to Semi-synthetic Castrol. When I used regular Dino it hovered just below. Just some 2 cents....
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Old 08-31-2001, 08:21 PM
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Thanks one and all for the responses. I drained the 10w 40 and swithched to 20 50 which brought the pressure up a little and gives me immediate response when I throttle. I had read a couple of items about the synthetics and will take your advise on the next chage.
Thanks again.
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Old 08-31-2001, 11:04 PM
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Location: Los Angeles, Calif, USA
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Worn out bearings can cause very low oil pressure at idle.

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Old 09-01-2001, 07:01 AM
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Thanks for the input David but the car has only 90k and the pressure problem began the first time i started the car after the oil and a/c vent accuator change. that was why I was concerned that the oil was incorrect or maybe I had disturbed a regulator or controller of some sor inside the dash when I had it apart.
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