One problem can lead to many other problems
On The Road AgainDecember 21, 2011 | 2,589 views | Post a comment
In an effort to stop an external oil leak, we had the oil pan off a 6.0-liter Chevy engine this week to reseal it with a new gasket. The only thing inside of an oil pan besides oil is a pickup tube that goes down into the “sump,” or the low place in the pan.
The oil pump sucks oil up through the pickup tube and pressurizes it against the bearings and other crucial parts of the engine, so it is considered a vital part. Once the pan was back on and the engine cranked, the low oil pressure light would come and go indicating low pressure.
Low oil pressure can be caused by a lot of factors, but this engine had good oil pressure before the pan was removed. Low oil pressure on any engine will destroy it if it gets low enough, as there isn’t sufficient lubrication to keep the engine parts from extreme friction. In doing some online research, it turns out that Chevy did a “bulletin” on the oil pickup tube O-ring on this engine -- the sealing device between the pickup tube and the oil pump.
It seems as if the O-ring flattens out over time, loses its seal, and the oil pump begins sucking in air instead of oil, starving the engine for lubrication. Once the pan was removed again, the pickup tube was removed, inspected, and was indeed pretty flat -- looking more like a band than an O-ring. Since the problem is common, the dealer had the part in stock and it was under $5. A simple sliding the old O-ring off and slipping the new one on by hand was the fix here, and the tube and pan were reinstalled.
The weird part of this scenario is we never unbolted or removed the oil pickup tube, but maybe bumped it around removing and replacing the pan. It was enough to break what little seal it had left, and the rest is history.
I bring this to your attention for two reasons. One, the Internet and dealer network are wonderful tools in helping diagnose cars and make common problems known, as discussed in a previous column. Two, if you happen to own one of these 6.0 engines, don’t let someone talk you into rebuilding it to correct a low oil pressure issue unless you are certain it is worn out and needs rebuilding. Not that most shops are crooked, but that this is a very unusual problem, and most shops would never suspect an O-ring to cause an oil pressure issue like this. Most oil pressure issues are the result of a bad oil pump, faulty sensor, or major bearing wear. The last one would make the engine a candidate for rebuilding.
Jeff is happy to respond to vehicle-maintenance questions from readers in this column. E-mail questions to firstname.lastname@example.org.