Oil warning light comes on 1 month after engine replacement


koebes

New member
I just had a rebuilt GoWesty Engine installed; drove it for the initial 1,000 miles as recommended; then had the recommended oil change and 1 day later, while driving on the interstate, the buzzing noise and the red light of the oil pressure sensor comes on. Stopped the car; checked the oil, temperature, all normal. Restarted the car, no red oil pressure light comes on, drove home. Drove it again 2 hours later, after 1/2 hour of driving, the same phenomenon: red light and buzzing sound. Stopped the car. Turned off the ignition. Restarted; everything is fine.
No funny sounds from the engine. Short of a problematic oil pressure sensor or faulty wire contacts, any other idea what might be happening?
 

tailu66

New member
If you have replaced the sensor then test the wire.
It could be a break in the wire or a tiny bare spot.
Be sure and go through all your grounds in the engine and under the dash.
This cures a lot of electrical problems.
 

RBEmerson

Member
Er, I rather doubt changing the oil viscosity is the fix.

See the attached oil diagram for a gas engine:
attachment.php

10W-30 is an acceptable oil grade, depending on operating temperatures.

I wonder if the oil level was too low and the oil change included bringing the oil level up to where it should be. If you were at the bottom of the acceptable level and burned off oil, you could easily have oil pressure problems. Who did the engine rebuild? Even if levels were right, chip contamination or (worst case) oil pump problems could cause the warning light. If the rebuilder didn't do a complete job... Not Good.

The take away here is to be 100% certain the problem has been corrected. Changing from one weight to another isn't likely to fix any but the most egregious of oil pressure problems.
 

koebes

New member
Thanks for the detailed input. I put the problem on ask.com and had a VW mechanic telling me that the wire from the oil pressure sensor to the dash needs to be replaced as it is grounding intermittently.

I of course checked the oil level everytime the light came on: right at the full level.

Now: the first 1,000 miles after engine replacement no problem. Immediately after the 1,000 mile oil change the light comes after driving for some time to reach operating temperature. Light goes out immediately when you restart the engine, only to come on later again. Oil sensor replaced, etc.

If there was a mechanical problem it should have shown immediately after the new engine was put in. But it didn't. First 1000 miles ran fine. Only after the 1000 mile oil change did it happen.

Now with 20W50 it has been running 1000 miles climbing hills and mountains without the light coming on once.

GoWesty lists a low viscosity oil as a problem for the light to come on.
 

RBEmerson

Member
Cardinal rule for troubleshooting: if there's a complicated explanation for a problem and a simple explanation for a problem, go with the simple explanation. In this case, check the wiring at the engine and follow it to the harness going forward. Unless something really, really unlucky happened, the chances of a wire failure in the harness are near zero. But a wire rattling around on the engine? Just about bet the dog and family farm on it.

On the oil viscosity thing... if the engine is too hot, the crank bearings are getting sloppy, and/or the oil pump is on its way out, then, yeah, low viscosity oil won't help keep the pressure and the light comes on. Unless the engine rebuild was poorly done, you've got a tight engine. Viscosity, the complicated explanation, isn't the problem. Look again at the recommended oil weights. Your original oil was fine unless you planned to run around a lot in the desert or on really hot summer days.

"Yeah, but it was all good for 1000 miles, they changed the oil and..." Wanna bet a wire was pinched or dinged during the oil change? Wanna guess which wire that was? Again, look at the easy solution first.

On "it was all good and now it's broke - why is that?" Hey, Uncle Harvey was doin' darn good for a 93 year old guy. Right up until the truck hit him. That's the nature of things, they work just fine until they don't. :)
 

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