Weather is getting hotter and hotter, and the low oil pressure problems start for us cab drivers.
Ok, lets start with the basics.
1.Bentley manual (AKA Bible) states that you must used 20W50 oil for summer and 10W30 for winter use. Or use 15W40 all year.
2.I prefer to use genuine VW filter or Bosch for peace of mind. Others will work well.
3. Verify you have no oil leaks. Usual suspects are the valve cover gasket and the oil pan.
There are two types of valve cover gaskets.The cork and the rubber one. I've used both and I found the rubber one to be the best.
This is the cork gasket
and the rubber type which comes with different studs.
Dynamic Oil Pressure system.
The dynamic oil pressure system is a circuit in the cluster that determines when the oil pressure is low. The easy way to remember which switch is high and low is to look at where they sit. The high pressure switch is right by the oil pump where the pressure is highest and the low pressure switch is in the head where it is the lowest. They work together to warn you with the flashing LED and the annoying buzzer.
The 2 switches work together. When the 0.3 bar switch detects pressure less than that, it creates a ground which triggers the led.
When the pressure is less than 1.8 bar the high pressure switch is grounded. When it goes over 1.8 it opens. The cluster is constantly checking to see if the ground with the high pressure switch is lost. If the tacho reads 2K and over and the ground is lost (pressure less than 1.8 bar) the led starts to flash and the buzzer goes off. Most people are annoyed by the buzzer and find ways to mute it.
These people are now looking for a replacement engine.
The system is trying to show you that something is wrong with the lubrication. When you see these symptoms, stop the engine immediately and verify that all wires are connected and if you have an oil pressure gauge that it reads 2bars at 2000rpm with the oil temp arround 90-100 degrees Celcius.
An easy way to rule out a deffective dual sender is to install a 0.3bar switch (blue in color) directly on the oil filter flange.
In this photo you see both holes occupied by allen bolts
Side view with optional water/oil exhange cooler setup
You should have two switches there currently. One for the oil temp and the high pressure switch. Right next to the high pressure switch you will see an allen bolt. This is where you can screw in your 0.3 bar switch. Extend the yellow cable going to the side of the block all the way to the oil flange and you are set. Now your dynamic oil pressure system is supposed to work 100%
If everything is connected, you have the appropriate oil/oil filter in the engine and the led is still blonking then its time to start worrying.
Either your oil pump pickup point is blocked or your main/rod bearing are showing their age. Best way to know for sure is to connect a mechanical oil pressure gauge on the side of the block and measure the real pressure. Maybe the wires going to the cluster have a problem somewhere and you are getting inaccurate readings.
This is a link on How to change your oil pump
if you change the oil pump and you are still experiencing low oil pressure then its obvious that the bearings need to be changed.
Thats not an easy task and should be the last thing you change after you rule out everything else.
Modified by Black_cabbie at 5:43 PM 6-20-2005