Exactly. This is not rocket science....and certainly does not need 30 posts of speculation. 
Sudden oil leak...
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Sudden oil leak...
As title says, I've developed an oil leak on the passenger side. It is a pretty substantial leak. As in it looks like a 1960s Harley Davidson had been parked in the garage, for awhile!! Had it on a 4 post lift, and it's hard to tell where it's coming from. It is NOT coming from the front or rear main seal, or the oil pressure sender. It appears to be coming from either:
A: Upper pan gasket,
B: Oil level sensor,
C: Crank position sensor, or
D: Maybe the dipstick tube O-ring.
Anyone ever have their oil level sensor leak? Mine is the original, 26 year old 2000 sensor. So, has anyone ever had their crank position sensor leak? Mine is at least 10 years old, maybe 20 years old. It is an LS7 block, so no cam sensor up above, as it's in the timing cover now. That said, the upper pan gasket is 10 years old. The lower pan gasket was changed by yours truly 3 or 4 years ago, but not the upper.
Lastly, anyone had their dipstick tube O-Ring start leaking? I hate to throw parts at it. But some of the stuff is getting old, and probably should be changed, anyway. Anyone have any thoughts on this? Thank you....
A: Upper pan gasket,
B: Oil level sensor,
C: Crank position sensor, or
D: Maybe the dipstick tube O-ring.
Anyone ever have their oil level sensor leak? Mine is the original, 26 year old 2000 sensor. So, has anyone ever had their crank position sensor leak? Mine is at least 10 years old, maybe 20 years old. It is an LS7 block, so no cam sensor up above, as it's in the timing cover now. That said, the upper pan gasket is 10 years old. The lower pan gasket was changed by yours truly 3 or 4 years ago, but not the upper.
Lastly, anyone had their dipstick tube O-Ring start leaking? I hate to throw parts at it. But some of the stuff is getting old, and probably should be changed, anyway. Anyone have any thoughts on this? Thank you....
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I think I've eliminated the crank position sensor and dipstick tube O-ring. Oh, everyone with the 1997-2000 will be happy to know that not only has GM discontinued the dipstick tube, which I already knew, but the Chevy dealer parts lady says you can't get the O-ring unless you buy the entire tube, which comes with said O-ring! 
I asked how can I get the O-ring if the tube isn't available. Of course she had no answer for that one!!That leaves either the upper pan gasket or the oil level sensor. If I had to pick between the two, I'm guessing upper pan gasket, as there is oil on top of the passenger side batwing of the pan, even forward of the dipstick tube, which is well forward of the level sensor. Is the upper pan gasket suspect after only 60,000 miles? What do you guys think? Thank you...
I asked how can I get the O-ring if the tube isn't available. Of course she had no answer for that one!!That leaves either the upper pan gasket or the oil level sensor. If I had to pick between the two, I'm guessing upper pan gasket, as there is oil on top of the passenger side batwing of the pan, even forward of the dipstick tube, which is well forward of the level sensor. Is the upper pan gasket suspect after only 60,000 miles? What do you guys think? Thank you...Last edited by grinder11; Apr 9, 2026 at 03:55 PM.
Le Mans Master
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I think I've eliminated the crank position sensor and dipstick tube O-ring. Oh, everyone with the 1997-2000 will be happy to know that not only has GM discontinued the dipstick tube, which I already knew, but the Chevy dealer parts lady says you can't get the O-ring unless you buy the entire tube, which comes with said O-ring! I asked how can I get the O-ring if the tube isn't available. Of course she had no answer for that one!!That leaves either the upper pan gasket or the oil level sensor. If I had to pick between the two, I'm guessing upper pan gasket, as there is oil on top of the passenger side batwing of the pan, even forward of the dipstick tube, which is well forward of the level sensor. Is the upper pan gasket suspect after only 60,000 miles? What do you guys think? Thank you...
I asked how can I get the O-ring if the tube isn't available. Of course she had no answer for that one!!That leaves either the upper pan gasket or the oil level sensor. If I had to pick between the two, I'm guessing upper pan gasket, as there is oil on top of the passenger side batwing of the pan, even forward of the dipstick tube, which is well forward of the level sensor. Is the upper pan gasket suspect after only 60,000 miles? What do you guys think? Thank you...
Get brake kleen spray the **** out of the area and add die to the oil. That will find the oil leak 100%
Drifting
Joined: Jul 2004
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From: Pingree Grove IL
Honestly, If your doing this yourself, I would love to come help and learn a few things, especially if your taking the oil pan down, valve covers off, sensors, or dipstick, but I live near Chicago, sorry Grinder.
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Thread Starter
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Can't do this in my Florida garage. Not allowed to do major repairs here, and the tools I need are 1,250 miles away. Just trying to get some educated guesses here, because I cant get under the car to do anything....
Tech Contributor
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From: Dyer, IN
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No. My main reason for posting this is to avoid being ripped off, because I've decided to have it repaired down here. I was quoted what I think is a pretty decent price to replace the upper pan gasket. It's a lot of work to get to the gasket. They want approximately $1,050. It would cost more to have it trailered to Michigan. If I drive it, it would substantially oil everything up underneath. After all these years, I do know how to check for oil leaks. But I can't get under the car down here to clean it or do the checking. So I appreciate any input as to what is the most likely cause. When I got the oil changed, we looked underneath and behind the engine. Front and rear seals appear OK, as do the oil pressure sender and valve cover gaskets. Valve cover gaskets are only a year old. I do appreciate all your opinions. Thanks, guys...
Running Guns & Moonshine
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From: CT
And at least it's fixable. But at the same time it is part artwork and not simply a bolt-in, walk away job for the shop. Make sure you give it run time, a few heat cycles and some revs / wot when hot before leaving town.
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Problem found and repaired. Shout out to R&B Auto Electric in St. Petersburg, Florida!! I thought I'd update the thread with the info. I had suspected it was either the upper pan gasket, or the dipstick tube O-ring, or both. Turns out it was just the O-ring, thank goodness. I had even called the Chevy dealer asking about a new dipstick tube O-ring. Of course, you have to buy the dipstick assembly in order to get the O-ring!! As most know, the dipstick assembly has been discontinued for many years, so Chevy dealer was useless (surprise!!
). R&B charged me $120 to find the leak, pull the dipstick assembly, install the new O-ring, and clean up a huge oiled up mess. This isn't the first time I've used R&B. They do good work. If you're in the Tampa, Florida area, and need help with your Vette, R&B is a go-to for me.
). R&B charged me $120 to find the leak, pull the dipstick assembly, install the new O-ring, and clean up a huge oiled up mess. This isn't the first time I've used R&B. They do good work. If you're in the Tampa, Florida area, and need help with your Vette, R&B is a go-to for me.
Burning Brakes
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From: Port Orchard, WA
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Good to hear that you got the oil leak fixed, especially at that price.
So I gotta ask - how common is this oil leak on C5s?
So I gotta ask - how common is this oil leak on C5s?
Le Mans Master
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Thread Starter
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It is my understanding that the OEM LS7 block, which is what I have in my car, is manufactured without the hole in the block where the dipstick would be inserted. The LS7 in the C6s are dry sump, with a dipstick in the oil tank. So the shop I bought the block from had to drill the block for the dipstick. Maybe they didn't use the correct procedure for drilling this hole. Perhaps they just drilled it. If I were doing the machining, I'd drill it slightly undersize first, and use a reamer to obtain a nice finish. But, on the other hand, maybe they did do this. The dipstick and O-ring are 26 years old! Nothing lasts forever. Yes, it is rare for this to happen. But it seems my car has had several rare problems manifest thru the years!!