Oil light on but engine sounds really good

Tiny
ATOMASI
  • MEMBER
  • 1998 VOLKSWAGEN PASSAT
  • 1.8L
  • 4 CYL
  • TURBO
  • FWD
  • AUTOMATIC
  • 137,000 MILES
Hello,
From research on all these threads, this oil pressure issue seems to be a huge issue in higher mileage VW/Audi 1.8T's. I just picked up one as a 2nd car to beat around town in and have the oil light coming on. It seems to come on and off, but the one consistent thing I've found is that it ONLY seems to come on once the engine warms up (10-15 min after starting). So, first thing I did was got an oil/filter change and the mechanic said the oil that came out didn't look too bad. Thinking this would resolve the issue, the light came back on 10 min after leaving the garage. Given the overall age and condition of the car, I can't really justify the cost/time of dropping the pan to clean/replace the pickup screen, etc. Does anyone know what the likelihood of this just being a bad sensor? There does not appear to be any knock or other sign of oil starvation, engine idles steady at approx. 800-850 rpm, acceleration is smooth/fine, etc. Any thoughts would be much appreciated!
Thanks!
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Saturday, September 20th, 2014 AT 8:47 AM

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Tiny
CARADIODOC
  • EXPERT
You're not willing to do a minor repair like check the pickup screen? Allow me to argue a couple of points, but understand I am definitely not a fan of VWs. First of all, the car is only about 1/3 used up, if that. With normal maintenance, it will run for a real long time yet. Second, you'll stick money for repairs into any car brand or model, (unless you ignore everything including oil changes for 12 years like I've done to my '88 Grand Caravan daily driver)! That's abuse, not neglect.

There's two things you can do first. Have a mechanic test the actual oil pressure with a mechanical gauge so you know exactly what it is when the engine is warm. If it's low, we'll have to go further. If it's normal, replace the sending unit. If you're going to spend money on that, might as well spend it on just the sending unit and replace it yourself as a test. I'm not aware of common problems, but if the sending unit takes care of it, we'll both be happy.

If the problem is still there, and with your dandy observation that it always takes about the same amount of time and engine temperature for the problem to occur, the first suspect would be worn engine bearings. A clue to this or a temporary fix might be to use a higher viscosity oil. I'm really not a fan of additives in a can to solve problems, but thicker oil will run through the bearings slower and that will help keep the pressure up. If that helps the problem, it is usually possible to replace the bearings without removing the engine. I did that on mine about ten years ago in a misguided attempt at solving a knocking noise, (which is still there today). The fact that you don't hear any noises suggests there's no damage to the crankshaft journals. Damage would destroy new bearings in a couple of miles.

You would need to know how to use "Plastigauge". It's actually pretty easy to use and explain. That will tell you how much clearance there is in the bearings. Recheck the clearance with a new bearing. If it's much smaller, the old bearing was worn. If it's the same but more than VW specifies, install "undersize" bearings. They are always available in standard undersizes. The common sizes are.001", .002", then.010", .020", etc.

Replacing bearings might be a little involved for all but the most experienced do-it-yourselfers, but that might be your only option if that's the route you choose. Most mechanics won't do jobs like that because they can't guarantee the quality of the repair.
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Sunday, September 21st, 2014 AT 11:20 PM

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