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This is a weird problem I have faced and there seems to be no solution to this even after having given the car to my mechanic 3 times. Whenever I drive my car uphill even for a little while, like 5-10 minutes, the engine oil light starts blinking, and keeps blinking. And as I go downhill/flat road for sometime, the light goes off by itself. And this keeps repeating everytime a uphill/downhill comes. Now my work is such that i have to travel to a uphill town and come back down to the plains often. It's around 200 km round journey. What could be the issue?

Some background: It's a 2012 VW Polo Diesel engine. I live in India, so the engine oil light is only red (not yellow and red like in Europe, I guess). I have got it serviced for this issue 3 times now in 2 months, but no end to it. The shop changed a seal, a gasket and whatnot. But nothing seems to fix it. Now the mechanic is telling me that it's due to the gradient. It does make sense, because that's what I have observed too, but this wasn't happening before, so why now?

Thanks a lot for the help.

2 Answers 2

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I have a VW TDI diesel, but an earlier model.

Your oil light comes on when there is a gradient but not because of a gradient. A mechanic who blames the tilt of the ground for the light on the dash should be given emergency oxygen because his brain is not working right. A car should be able to drive on any road gradient without warning lights!

  1. If the mechanic has not yet tested oil pressure, you need a better mechanic. It’s very easy and not an expensive or time consuming test. I think it is a mandatory first step if your oil light is blinking because a true lack of oil pressure can destroy your engine. Doing the test is cheap insurance.

  2. The VW oil pressure sending unit is a simple on-off switch. It does not measure pressure as a number, but simply as “good” or “low”. The sending unit can lose its calibration, so if your oil pressure is known to be good but the light comes on, replace the sending unit. It is inexpensive and easy to replace. While it is being replaced, the mechanic should check the connector. The unit can develop an internal leak and spill oil into the connector. If this has happened, the connector should be replaced because oil degrades it.

If there is an actual loss of oil pressure while climbing a hill --

  1. Has the mechanic dropped the oil pan? The oil pick-up tube (clearly visible with the oil pan removed) has a mesh screen on the end, and it can become clogged with debris. This should be checked and the screen cleaned if clogged.

  2. Is the oil pickup tube cracked anywhere along its length, is it loose or is the gasket degraded? If so, the tube will suck air and affect oil pressure at higher rpm. If it is cracked, replace it; if loose, tighten it; if the gasket is bad, replace it.

  3. If oil pressure and the sending unit and connector are good and there is no problem with the pickup tube, consider that you may have the infamous “VW harness chafing”. Search those words online to learn more. In brief, somewhere in the car – sometimes in the wiring harness under the battery – some part is rubbing on a wiring harness and has worn through the insulation. It can become apparent only when the engine is making enough torque -- such as going uphill -- that it twists on its mounts and pulls a wire to cause a short or open circuit. This can cause all sorts of havoc such as dash instruments going crazy or warning lights coming on.

EDIT follows:

  1. Some oil pans have a baffle to keep the oil from sloshing around too much. I don't know if your oil pan has a baffle. If the baffle comes loose and it is moving around, certain car motions such as climbing a hill can cause the baffle to move under the oil pickup tube and block it. This would cause a loss of oil pressure. Easy to check this when the oil pan is dropped.
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    One time I put my BMC Mini into the shop because the oil pressure warning light was on, but the oil level was correct. When I picked up the car the mechanic said "I ran a pressure test, and it is OK." I replied "But the oil pressure warning light is still on," "Yes, but it's OK" ... "Er, how will I know when it's not OK?" I had to rebook for next day to change the faulty sensor. Grrr. Commented May 23, 2023 at 18:15
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Obviously, first, check your oil level (regardless of having checked it earlier in the day). You might have developed a serious leak and be minutes away from wrecking the engine. But assuming the oil is fine ,...

I once had the same problem on a different car. Replacing the oil pressuire sensor was easy and it wasn't an expensive item, so I did that myself on the basis that it was the most likely problem (and not expensive if it was a wrong guess).

It was the right guess.

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