1999 VW beetle 2.0 bubbles in Mobil 0w40

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Dec 11, 2013
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illinois
about a month ago weather was crazy cold so I started the '99 vw beetle with a 2.0 aeg engine and left it idle for about 20 minutes before I was ready to go. Drove about 10 miles on the highway and the oil light came on. The oil only had about 500 miles on it. I got the car with no history of what had been used in the car prior. When i changed it I used Mobil 1 synthetic 0w40. The oil light would go away when RPM's were less the 2000 but came back when over 2000 RPM's. When I got to a safe area to stop I checked the oil and it was "frothy" lots of bubbles. Fast forward a few days later checked the oil and it looked perfectly normal and the level was correct. Drove fine with no issues. Over the past few weeks put several hundred miles on it with no further issues. Today it was single digit weather again. started the VW and left it idle about 20 minutes while I cleared the snow. Took the bug for a ride and the oil light came on within a few miles. Brought it back home and the oil wasn't as Bubbly as last month but definitely had bubbles. Let it be for a couple hours while I went and cleared more snow. when I got home I checked the oil and it looked fin (no bubbles and correct level). Took it for a 5 mile drive with no problems- no oil light coming on. Any suggestions of what is going on? Is the 0w40 not right for it? should I be using 5w or 10w? The car runs great. It has about 118,500 miles.
 
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Aug 26, 2013
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DE
is that oil within the manufacturer's specification? you are checking the oil on level ground with the engine off right?
 
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Denmark
I i remember right. Those engines have 2 oilpressure censors. One for lower range rpm and one for higher range rpm. If the one for the higher rpm range goes out. It will turn the light when it gets som rpm,s
 

jimzz2008

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illinois
I might add the only 2 times I saw this happening is after leaving the car "warm up" and idle for 20-30 minutes in the driveway. Does this have any thing to do with the bubbles? any other time I get in and go, or maybe a 5 minute idle before leaving
 
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Sounds like maybe a bad oil pressure sensor and the bubbles are just there because you check the oil so soon after shutdown?
 
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Just a guess here. Froth sounds like some coolant may be getting into the oil. Head gasket could be leaking due to the cold. Sounds like the problem is going away as the engine heats up to operating temp.
 

jimzz2008

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Dec 11, 2013
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illinois
Originally Posted By: SilverC6
Just a guess here. Froth sounds like some coolant may be getting into the oil. Head gasket could be leaking due to the cold. Sounds like the problem is going away as the engine heats up to operating temp.
I originally thought Head gasket, but when the oil returned to its normal state after sitting and the coolant level hasnt changed, I dismissed the head gasket. The car runs awesome. I am thinking the sensor as well, which I plan on changing with the next oil change. I am confused as to why the couple times I had issue with the oil light coming on was after a Long warmup period in the driveway idling.
 
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