Sudden loss of oil pressure.

'96 B4 Passat. About three miles from home the oil pressure alarm went off, I shut it down and pulled over immediately. No loss of oil, no leaks, didn't see or hear anything unusual. I did notice it was unusually rough to start, cranking longer than usual. I also restarted it briefly after checking things over and it did so without hesitation. I was getting just under 10 psi on the gauge at idle, then shut it down and had it towed home.

This is only the second time in 14 years this car has left me stranded, so I'm not even that mad, honestly. Last time it was the intermediate shaft which broke its flange, so that was replaced along with its bearings (and pretty much everything else). So I'm thinking oil pump itself? Or could this be something like a blockage or collapsed filter? I haven't had time to tear it apart yet and would like suggestions to troubleshoot.

This sounds a bit like the classic "my oil pressure light came on after being out on the highway", since it sounds like you didn't lose oil pressure completely (the reference to 10 psi at idle?).

If so, some thoughts here:

http://vincewaldon.com/index.php?option=com_content&task=view&id=40&Itemid=28

Vince Waldon said:

This sounds a bit like the classic "my oil pressure light came on after being out on the highway", since it sounds like you didn't lose oil pressure completely (the reference to 10 psi at idle?).

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Not a complete loss in pressure, but far below what I've ever seen. It had only been running a few minutes at temperatures just above freezing, when I'd expect 30+ psi at idle.

Ok, another suspect would be the oil pump drive tangs on the bottom of the vacuum pump drive shaft. On high mileage engines they can be worn to the point of skipping, especially when the engine is cold and the oil is thick.

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Have you done any work to it lately? I had 0 oil pressure when the vacuum pump retaining collar bolt worked loose because I didn't tighten it securely after doing some work that required it to be removed.

I haven't done any work on it lately, but that sounds like a good place to check. I'll probably take a look later today.

glenn1179 said:

I had 0 oil pressure when the vacuum pump retaining collar bolt worked loose...

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Well that's a relief, this is exactly what the problem was. I pulled the pump to inspect the gears, and everything looked fine, cleaned it all and put some Loctite on that bolt! Started right up with 60 psi on the gauge. Thanks for the tip, easy fix.

Cool! Glad I could help.