My wife's '91 has a real low idle speed (650 rpm) and when I switched it to 5w-40 Mobil 1 from the 15w-40 non synthetic Rottela T the oil pressure is dropping to 0 at idle when engine is hot, before it seldom dropped below 1 for a hot engine. If I remember correctly .3 is min allowed. I was wondering if the idle was too low but the OM says it is where it should be. Looks like I will grab some RT 15w-40 today and change it back. That is only oil it ever had in the engine till now. First time I ever run across that problem in a MB diesel.

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'10 Chrysler T&C Stow-N-Go White. Grandpa's ride.

'13 Chrysler 200 Touring Candy Red. Grandma's ride.

Age and cunning will always over come youth and vigor.

The idle should be computer controlled. Somebody who knows where the adjustment knob is will chime in soon.

I thought it was ECM controled also, but I am not sure. I thought I read somewhere it was suppose to idle at 650 rpm but I can find it listed anywhere, although I did find in the OM that .3 was min for oil pressure on hot engine.

Man I am so not looking forward to changing the oil in 100*+ temps and 90% humidity. At least I have the Fumoto drain valve on the pan to make it easier to drain.

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'10 Chrysler T&C Stow-N-Go White. Grandpa's ride.

'13 Chrysler 200 Touring Candy Red. Grandma's ride.

Age and cunning will always over come youth and vigor.

Idle speed should be about 600-650RPM at hot idle. When starting a cold engine, the EDS will hold the idle at 800-900. So it sounds like your idle speed is up to spec. When the EDS is not functioning (i.e. with the key off and the shutoff valve disconnected), the idle speed drops to 500RPM.

I just switched to Mobil1 5W-40 (repackaged Delvac1 5W-40) from whatever diesel 15W-40 the indy put in it and it hasn't resulted in a drop in oil pressure. Hot idle is between 1.2 and 1.5 bar. Cold idle oil pressure is always pegged at 3 bar. I'd check the sensor and make sure it's not failing. Even though when they fail they usually show 3 bar, I'd still have a look at it before digging further...because fixing low oil pressure issues can get expen$ive

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I am going to put the 15w-40 for now in the morning and then order a sensor, kills me to think I am dumping $45 worth of oil. It just seems unusual that it would drop so much is all with the switch, never had it drop that much before when changing over to synthetic oil in older cars.

Man the Mobil 1 sure did clean out the valve cover area and it shines like a new silver dollar in side. So at least it had some positive effect.

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'10 Chrysler T&C Stow-N-Go White. Grandpa's ride.

'13 Chrysler 200 Touring Candy Red. Grandma's ride.

Age and cunning will always over come youth and vigor.

I agree that pressure is much too low, hopefully it's just the sender. I just had a lose of oil pressure with my 617 a few weeks ago, I ended up replacing the oil pump. AFAIK, they all run around 1.5 bar, even with 5W40 synthetic.

I wouldn't change the oil, that's not your problem. Either you have a bad sender or your pressure is really too low, changing the oil isn't going to fix either problem. If it really needs 15W40 to maintain pressure you need to have the actual problem diagnosed.

Bet that would get expensive if you have the work done. On mine it would require dropping front cross member or pulling the engine.

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'10 Chrysler T&C Stow-N-Go White. Grandpa's ride.

'13 Chrysler 200 Touring Candy Red. Grandma's ride.

Age and cunning will always over come youth and vigor.

It's not as bad on a W123, but the pump costs $5-600. The whole thing ended up costing around $1000.

I'm wondering if maybe the Mobil 1 cleaned everything out and my filter is clogged? I think I will give that a try as I have a couple extra's in the garage and that won't take but about 10 minutes and might tell me something.

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'10 Chrysler T&C Stow-N-Go White. Grandpa's ride.

'13 Chrysler 200 Touring Candy Red. Grandma's ride.

Age and cunning will always over come youth and vigor.

Possible, but I doubt it. Also, check the connection on the sender to make sure you didn't loosen it.

Well I drove the car this AM after changing the oil filter last night. The filter was lot heavier then normal, like it was still full of oil. I changed the filter after it had been sitting little over 6 hours, and the dipstick showed it was about pint low when I checked. I wonder if mobil 1 cleaned out a lot of old sludge type crap into the filter.

Anyway this am I drove the car about 10 miles in both city and highway w/o it dropping below 1, but there was another big differance. The air temp was about 25*F cooler then yesterday when low oil pressure was noted, although I can not figure how any outside temp can effect oil viscosity other then at start up. Once oil is at operating temp of 350* or more, I was always told outside air temp was of no real concern except at idle in extreem cold weather when engine might cool too much and the engine might over fuel and pass uburned gas or in this case diesel into oil pan.

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'10 Chrysler T&C Stow-N-Go White. Grandpa's ride.

'13 Chrysler 200 Touring Candy Red. Grandma's ride.

Age and cunning will always over come youth and vigor.

Oil pressure sending unit is on the filter housing.

Possibly the thermostat inside the filter housing wasn't opening allowing the oil cooler to function properly.

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Well this morning after 10 miles in 80*F weather and coolant at 82*C the oil pressure is staying at or slightly above 1, so maybe the cleaning action of the Mobil 1 5w-40 was a factor and just clogged the filter. Anyway I ordered 3 new MB filters from the dealer yesterday ($37.02 delivered) and will keep an eye on the car and change the filter as needed. I suspect I will change the filter again in less then a 1000 miles and may have to do it several times if the innards were in worse shape then I had thought.

Hey I checked into the sending unit and $31 is kind of high, but OEM list is $75 or there abouts. I would need to put car up on a rack from the looks of the location. I will probably replace it after the first of the year even if all goes well with engine and oil preasure readings.

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'10 Chrysler T&C Stow-N-Go White. Grandpa's ride.

'13 Chrysler 200 Touring Candy Red. Grandma's ride.

Age and cunning will always over come youth and vigor.

Idle speed (@ 60-80C coolant temperature) is 680 +/- 20 rpm

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