Hi Guys,

At just a little over 200k miles, I brought my car to the local indy due to plugs fouling in several cylinders. It was diagnosed with worn valve guides and having low compression in a couple cylinders. A leakdown test was also done, but I don't know the results. The head was taken off for machine work and the pistons were soaked in a magic concoction (I don't know what they used), which apparently freed the rings and brought compression levels back up. The timing chain, waterpump, and belt tensioner were also replaced as they were worn out.

The main issue that I'm still having now is with low oil pressure when the engine is idle. At cold startup, I get 3 bars in a couple of seconds. As the coolant temperature rises to 80, pressure drops to less than 1 bar. When coolant temperature is 100, pressure drops to zero or very near zero. The owner's manual specifies that .3bar is acceptable, but I really don't know where .3bar is on the gauge since there's no mark for this. I'm pretty sure that the oil pressure sender isn't the problem, since I've recently swapped it out for a new one (VDO). There are no noises from the lifters, and pressure rises immediately when rpm's go up.

I asked my indy about this, and was told that it's normal. The shop used 10w-30 dino oil, but I've had similar results using 15w-40 in the past. I've made an appointment for them to check the pressure using a mechanical gauge but haven't had a chance to bring the car back to the shop yet.

From what I've read, low oil pressure could be caused by worn bearings. Is there a temporary fix available for this, maybe running thicker oil would help?

My oil pressure gauge went to 0 at idle before replacing the oil pressure sending unit.


After replacing the sending unit, it will hover around .5 bar at idle.

__________________
-Justin

91 560 SEC AMG - other dogs dd
01 Honda S2000 - dogs dd
07 MB ML320 CDI - dd
16 Lexus IS250 - wifes dd

it's automatic.

Can't help on the mechanicals, but shouldn't you really be running about 20W-50 oil where you live?

__________________
1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't

If there really was no oil pressure, the engine would be toast in short order. Replacing the sending unit showed the real picture for me. It is on the oil filter housing and is an easy R&R. Cheap too.

__________________
Best Regards,
Sam

'76 280 Time Capsule
'00 S430 Long Trips
'91 190E Seeing how far it will go. 366k
'04 American Eagle Motorcoach

The question is not whether there is no oil pressure but whether it's inadequate. He has already replaced the sending unit with a new one. I too would try 20-50 weight oil, no harm where you live, then I'd stop worrying about it.

I thought the needle should hover around.5 at idle and peg at 3 when the rpms go up as in normal driving. Isn't this pretty much true in all MBs?

__________________
" We have nothing to fear but the main stream media itself . . . ."- Adapted from Franklin D Roosevelt for the 21st century

OBK #55

1998 Lincoln Continental - Sold
Max 1984 300TD 285,000 miles - Sold
The Dee8gonator 1987 560SEC 196,000 miles - Sold
Orgasmatron - 2006 CLS500 90,000 miles
2002 C320 Wagon 122,000 miles
2016 AMG GTS 12,000 miles

Of the 3 gas and 4 diesel Mercedes I've owned, I've always experienced well above 1bar hot & idling oil pressure. 5 of these 7 cars were 124s, one an M103, all were over 100,000miles when sold and most over 200,000miles.

Seems like there's something wrong, whether it is the oil pressure, the sender, or the gauge(voltage) it seems inadequate.

Maybe I should try some non-synthetic oil to see if my pressure drops? Where do you buy the stuff?

__________________

Gone to the dark side

- Jeff

Our 300E gets down to about 1.1 bar or so at a warm idle (well, in these temps...we'll see in the summer)....running 0w40 Mobil 1.......soon I am switching it over to Rotella 5w40 though, we'll see if that affects anything at all.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

The first thing you need to do is to temporarily install a mechanical gage and verify the reading.

I've recently seen a M103 engine get toasted because of low oil pressure, it was assumed that the gage was faulty. It was not....

The pump is run by a chain off the crankshaft. It's unlikely that the drive has failed, since you do get oil pressure at startup.

Potential problem areas are the pump itself, clogged pickup screen or a failed pressure relief.

Get it checked out posthaste before any damage is done.

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

Hi guys,

Thanks for the quick replies! I'm going to see if I can borrow a mechanical gauge and check it out myself. Regarding the oil, most shops (not mercedes-specific) here fill with 5w-30. I've rarely seen anyone carry 20w-50, but I'll try it out if I can find some.

Alienman,

You said the head was removed and machined. Was the oil pressure problem evident at first start up after the head was replaced? Was the correct head gasket used? Threaded plugs from oil galleries in place?

Just a thought.

TCG

Hi TCG,

Thanks for your input! The gauge was displaying low oil pressure prior to the head being done, which is why I replaced the sender recently while I was under the car doing the tranny filter.

Unfortunately, I don't know if the correct head gasket was used or anything about the threaded plugs. I was told that the engine's bottom end was toast and that it would be swapped out for one with much lower miles and known good service history, but for some reason or other they just did the head. As a precaution, I haven't driven the car since my initial posting and am crossing my fingers, hoping for the best.