000-668

I am experiencing problem with the oil pressure gauage needle in my 99 S500.

Battery was totally drained over the winter month, and a new battery was installed recently. Notice the gauge needle work occasionally but not all the time. It was not moving after the battery is reconnected, but after one day, the needle is moving as normal. After stopping at an intersection today, the needle stay at zero again and not moving any more. Car is running fine. Check oil level, all is good. Not red light on the cluster.

Any suggestion where to start checking for problem. Not sure if it is the sending unit need to be replaced. I think the gauge inside the cluster is working, but not sure how to tell.

Please assist. Thanks

oldsinner111

Sending unit do wear out or grease gets on the contact where it plugs to wire.

000-668

I noticed this condition, when the engine is cold, ie after the vehicle had an overnight rest, or not driven for a few hours, the gauge needle works. After the engine warms up, all of a sudden the needle drops to zero and won't move until the engine cools down again.

Logically I eliminate that it is not a gauge problem.

btw The vehicle was not driven for the past winter months. Just put in a new battery two days ago as the old one is completely drained and its the original battery.

Maybe the engine oil and the oil filter clogged up not having the engine running for quite some time. Plan to do an oil change with new filter to see if the problem will go away.

Check with dealer for oil pressure sender unit, its $144 for the part. Maybe that will be the next thing to do.

oldsinner111

Try rockauto .com for parts.I ordered one but did not replace as battery had to be disconnected.You get all kind of problems disconnecting battery.PS quit driving car until you verify you have oil pressure.

000-668

Finally the needle not even moving when engine is cold. My mechanic mentioned that it can be the pressure release unit but diagnostic shows defective oil pressure sending unit. Everything is back to normal after install the new part.

oldsinner111

Oh if they'd only listen.Been Mechanic over 35 years.

hellah fresh

I have the same problem as yours but whenever it is really hot out my temp needles drops down to 0 and the red light comes on. Did you just replace the sensor? how much was it?

000-668

Yes the sensor was replaced. However there was no RED light comes on in my case. Just no movement of the oil pressure gauge needle. With the RED light it may be some other complication.

Total cost is around $300, part and labor for replacement of sensor plus labour for oil change, excluding oil and oil filter which I brought in myself.

oldsinner111

With the RED light it may be some other complication.
I haved or read somewhere that one of the S engines sometimes would wear out the pump.It would put so much metal out that it would clog the oil pickup screen.Solution is a larger pump from a AMG 5.5,fill oil pan with one gallon gasoline,after draining oil,and shaking car to clear screen.
I hope this helps some as I have cleaned many oil screens that way.