Questions and Answers

Volkswagen Jetta Oil Pressure Q. Thanks for having this site. I have a 1991 Volkswagen Jetta, 1.8 liter, 8 valve PF engine with about 160,000 miles that has developed a low oil pressure problem. When I first noticed that the oil light was coming on fairly consistently after the car had been driven on the highway, I installed a mechanical pressure gauge to verify the pressure alarm.

Here is what I have observed. When the car is cold, the pressure will be around 60 psi. As the engine warms to full operating temperature, the oil pressure will gradually fall to below 20 psi. If I drive the car on the highway, the oil pressure will read approximately 22 psi at 60 mph. If I stop, the pressure will fall to about 5 psi at idle.

Other than the low oil pressure, the engine runs great. Because I was concerned about the low pressure, I replaced the oil pump but there was no improvement in the oil pressure. I just finished replacing the rod bearings with standard bearings to see if that was possibly the problem.

To be honest, I didn't think they were the problem. I knew this because I Plastiguaged the old bearing and they were within the .0047" wear limit. The rod journals looked good with no obvious scoring or wear. Changing the bearings was relatively easy to do and I just wanted to eliminate that possibility.

Any other solutions or should I be looking at an engine rebuild? How will I know which component is responsible for the low oil pressure? I am concerned that I won't find the cause and will still have low oil pressure after a rebuild. Or, should I just go with a remanufactured engine?

Thanks,
Tom

A. Normal oil pressure for that engine is 29 psi @ 2,000 rpm.

The rod bearings are not usually the cause of low oil pressure, it's the main crankshaft bearings that most often cause the low oil pressure problem you describe. To replace these you'll need to tear down the whole engine to do it right.

If the engine has a lot of miles on it, then maybe a remanufactured engine is the thing to do.