[Sincity]

I only have this car in my possession for the past 3 months. I have observed that sometimes, during idle at a stop light after the engine has warmed up, the gauge reads at 2 and when I drive, it goes back to 3. When I start the car in the am and during idle, the gauge is at 3. Is something "stuck" causing it to be at 2 during idle at the light after the motor is warm? Or is this normal? It also sometimes "twtiches/bounces" back and forth around 2 a couple of times and then settles at 2.

The car had a valve job 18k mi ago. The rings were supposedley (sp?) checked during that time.

 

[shingleback]

Sounds perfectly normal to me.

When the engine is cold, the clearances between moving parts are at minimum and the oil is more viscous, resulting in a higher working pressure. As the engine and oil warm up, the clearances increase and the oil viscosity decreases, so at idle you would expect to see a slightly lower pressure. On these cars, they tend to be at 2.

One does not need to worry unless the pressure is high with a cold engine, but is really low (< 0.5?) with the engine at operating temperature of 80 degrees...that would indicate major engine wear.

 

[Sincity]

Oh good. Thanks for answering, shingleback.

 

[raed_jan]

Souldn't be at 3 always once you start the engine!!!

 

[284037]

Souldn't be at 3 always once you start the engine!!!

Was that suppose to be a question?
Mine does go to 3 when started then drops to 1/2 or even 1 bar at idle. When I hit the gas it goes back to 3, so I think that's normal. My 560SEL is a 3 no matter if I am at idle or pushing the gas but I think it's a bad oil pressure sensor (sender). My RX7 has a much better oil gauge and is much more sensitive where I can see the oil pressure rise or fall proportionally to my driving.

 

[click the pirate]

First of all you have to consider the oil pumps position, in a 190 the oil pump is in the timing cover, this is an aluminum cover so its going to change dimensions alot faster due to temp changes, in the 560 it has a conventional cast iron oil pump that is in the oil pan. It is going to be alot more stable.

As long as the lifters are not making noise at idle, I would say that you have enough oul pressure. If you are in doubt, you can hook up a mechanical gauge. Rule of thumb is 10psi of oil pressure for every 1k RPM, so anything at 15 or more at ilde is enough, but keep in mind this is a "rule of thumb" its not written in stone. If you are not comfortable with the oild pressure, get a new set of rod and main bearings.... provided there is minimal crankshaft wear, that will increase oild pressure.

 

[n0alpha]

Note also that the oil pressure sensor (which is located beneath the oil filter) can get dirty and give false readings. They're very difficult to clean, and are best to be replaced if they have failed.