C220 No oil pressure

[Derm]

Hi

I have a 94 E220 with 160k. Recently I have noticed oil pressure dropping to zero on tickover 800RPM when engine is warm (80Deg c). Normal driving steady at 3 Bar . Good pressure when cold . Could this be a gauge fault engine sounds ok. Would appreciate any advice.

Thanks
Derm

 

[Number_Cruncher]

Check that the oil pressure relief valve is not sticking partly open.

As long as you have over 0.3 - 0.5 Bar at hot tick over, and you reach 3 Bar by 2000 rpm, it's within spec.

 

[Derm]

I think it can go to zero. Can pressure relief valve be accessed from the outside of the block. Would a lower viscosity oil help I am using 15/40.

Thanks Derem

 

[Number_Cruncher]

The pressure relief valve is part of the oil pump, and you'll need to take the sump off to get to it. The advantage of this being you'll also be able to check the oil strainer on the inlet to the oil pump at the same time.

Don't consider changing the oil type to one that isn' recommended by MB.

 

[42864]

First thing to do I would think is to carry out an Oil and Filter change, perhaps the Oil if has not been changed for a while is getting a bit tired. If you do go down this route, ensure that you use a Genuine Mercedes Oil Filter, some pattern filters have been known to give a false Oil Pressure reading.

 

[television]

We have never had an oil pressure relief valve fault, the other thing is the sender unit, this could have gone out of line.

Normally in these cases one unscrews the sender and fits a pressure gauge,,that is the only real way to tell whats going on

 

[Stu_CDX]

I know we're talking different cars, but are we all sure that it can go to 0.3 on the scale?

I was considering taking my W124 to be checked out when it dropped below 2 (Just), after a hard run. Lol.

 

[Derm]

Thanks for the comments. I have a pressure gauge just need a union to fit block i know sender has 11mm coarse thread any one know what it is?
oil filter came from Europarts earlier this year only done about 6k miles since and have only noticed a change recently.
This did happen last year after a long run to devon but has been ok since.

Derm

 

[television]

You are running at the correct pressure, ignore the odd glitch.

The oil line fittings are I believe standard water/gas/air threads

 

[Number_Cruncher]

If the pressure comes up when the car is revved, then, that suggests the sender & gauge are working, but, a mechanical gauge is a good backup check.

If the pressure does rise when revved, it also means that the oil pump drive chain is OK.

Oil doesn't get "tired" to the extent that the oil pressure just disappears!

Needless to say, a hot oil pressure of 2 Bar would be perfectly acceptable.

On some engines, there are O ring seals in the filter housing which can fail giving low pressure, I'm not sure if that is true in this case.

 

[Derm]

Hi

Just to update oil pressure still on zero most of the time I think it must be the sensor! Car still running well so not too worried at this stage.
Interestingly when sensor is disconnected oil pressure shows 3 bar I assume this is normal
Thanks for all the comments