Help me find this oil leak please!

[mattbta]

Valley pan is under the intake manifold. Your knock sensors screw into it.

 

[bottomline2000]

Right in front of the oil pressure sensor. If you not seeing oil by the sender it's more than likely,ely not the valley tray or cam sensor. Crank sensor is right behind the starter. Do you have a check engine light by chance?

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[John03Z71]

Right in front of the oil pressure sensor. If you not seeing oil by the sender it's more than likely,ely not the valley tray or cam sensor. Crank sensor is right behind the starter. Do you have a check engine light by chance?

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I had a check engine light a couple weeks ago that stayed on for about 3 days then went off, hasn't come back on since. I did check the crank sensor behind the starter, no leaks there.

 

[bottomline2000]

I had a check engine light a couple weeks ago that stayed on for about 3 days then went off, hasn't come back on since. I did check the crank sensor behind the starter, no leaks there.

Reason I asked about the check engine light is you may have clogged cats. This may be cause the heads to pressurize and force oil out the valve covers. Path of least resistance. My cats were clogged bad in my old engine and the thing seeped oil everyway possible. Eventually coated the engine..

If it's dripping there has got to be an obvious source. Did they check to see is the rear plate was properly aligned before putting in the new seal? I have the plate alignment tools from Sac City Corvette and I haven't had any issues with leaks. I didn't want to chance having to do it twice..

The gray piece is the alignment tool, but the plate has a big gasket around it too..if they removed the plate they need to RTV the corners connected to the oil pan or you will have a bad leak..

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[John03Z71]

Reason I asked about the check engine light is you may have clogged cats. This may be cause the heads to pressurize and force oil out the valve covers. Path of least resistance. My cats were clogged bad in my old engine and the thing seeped oil everyway possible. Eventually coated the engine..

If it's dripping there has got to be an obvious source. Did they check to see is the rear plate was properly aligned before putting in the new seal? I have the plate alignment tools from Sac City Corvette and I haven't had any issues with leaks. I didn't want to chance having to do it twice..

The gray piece is the alignment tool, but the plate has a big gasket around it too..if they removed the plate they need to RTV the corners connected to the oil pan or you will have a bad leak..

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Thanks for the input. What other symptoms would be present if cats were clogged? Idle has been a bit rough and also fast/heavy acceleration, without flooring it (staying in same gear), is pretty sluggish and “jerky”, especially noticed it this summer when a/c compressor would be on it would be much more prominent.

Don’t want to derail off original topic too much, no an alignment tool wasn’t used when we did the rear main, and RTV was used.

Thanks again

 

[bottomline2000]

Thanks for the input. What other symptoms would be present if cats were clogged? Idle has been a bit rough and also fast/heavy acceleration, without flooring it (staying in same gear), is pretty sluggish and “jerky”, especially noticed it this summer when a/c compressor would be on it would be much more prominent.

Don’t want to derail off original topic too much, no an alignment tool wasn’t used when we did the rear main, and RTV was used.

Thanks again

Honestly everything you described could be signs of your cats going bad. If you are down on power already it's gonna be more noticeable with the extra parasitic drag from tye ac compressor.

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[treehan77]

so did you ever get it to stop leaking? mine does the same- first sign of oil after cleanup always on the inside starter bolt. changed the oil pressure switch - no change. the sensor above the starter was dry. flywheel is dry.

 

[John03Z71]

so did you ever get it to stop leaking? mine does the same- first sign of oil after cleanup always on the inside starter bolt. changed the oil pressure switch - no change. the sensor above the starter was dry. flywheel is dry.

Yes, if you scroll up a handful of posts it turned out to be my rear main. I popped the inspection cover off the flywheel and it appeared mostly dry but a reputable shop pointed out some oil collecting around the bottom/inside area and others that weren’t so easy to spot at first glance. I still have some minor leaks at the front timing cover area but nothing near as bad as the faucet leak that was my rear main. I found a “shade tree” mechanic to do mine in my driveway on a Sunday afternoon for a fraction of what a shop would have charged / what I was quoted.

 

[treehan77]

Decided to try this cheap endoscope somebody gave me to check for oil back by the camshaft position sensor, oil pressure sensor, etc. I know it’s blurry, but it looks like oil to me. I swapped the oil unit before. Anybody else think this looks like my leak?

 

[treehan77]

Maybe the video is better... what do you guys think?

 

[SnowDrifter]

1. Whoever did the work is a ******* idiot and they're trying to pawn off bad work. I'd look into getting your money back. Replacing an oil pan gasket doesn't cause more 'pressure' anywhere else. They're bullshitting you hoping you go away

2. Clogged cats won't cause an oil leak. It'll do a whole lot of things, but an oil leak isn't one of them.

3. Look into a UV dye kit if you're having trouble locating it. That much oil coming out of the motor, I can't see this being all that elusive to find

4. How's you PCV valve? If that's plugged you can run into some leak issues

 

[John03Z71]

Reviving this thread from almost exactly a year ago, as my leaks never completely went away and now it's quite bad again. I'm losing about a quart of oil per week now (about 250 miles +/-). Seems to be more in the front of the engine this time as everything up front is soaked in oil, and I think the light amounts on the rear are just from blowback on the highway.

Here's what I have replaced:
Rear main seal, oil pan gasket, oil cooler block off plate seal (last year)
Oil pressure sensor (several years ago)

When the shop that did my oil pan gasket had it in there last year they told me my timing cover gasket was starting to leak a little, so I'm thinking that may be the culprit. Is this the same thing one might refer to as the "front main seal"? The shade tree mechanic that helped me with my rear main job last year told me the front main was starting to leak a bit.

Valve cover gasket on passenger side shows a little bit of dampness beneath it but definitely not shiny wet with oil or anything.

So I guess my question is, besides what I've already done (and valve cover gaskets) what else is left that could be the culprit? Everything is covered in so much oil it's very hard to visibly tell, I might have to get a UV dye kit. Also if the timing cover is the culprit, how hard is the job for a fairly competent DIY'er with basic tools? And how many hours labor would a shop likely charge?

Thanks in advance!

 

[SnowDrifter]

Clean it up and look around. Not trying to be a smartass but we don't have a crystal ball that'll tell us which gasket has failed based on the description of a dirty engine. If you're unwilling or unable to look around, then the forums really aren't your best bet for this and you'd be best off taking it to a trusted mechanic. All we could do is speculate. Someone, somewhere, needs to get hands on with your rig.

Timing cover needs to come off to do said gasket. Front crank seal is pressed into the timing cover. It would be prudent to do both at the same time if you find that's the issue.


Run down of the gaskets and other oil contacted components that are in your engine, more or less in order from top to bottom:

- Valve cover gaskets, including grommets and PCV system
- Oil pressure sending unit, camshaft position sensor
- Valley pan gasket, including grommets for knock sensors. Located under the intake manifold
- Front and rear covers, including front/rear main seals which are pressed in
- Oil galley plug on the front left side of the engine roughly at the same elevation as the crank, crankshaft position sensor located by the started
- Oil cooler lines or block off plate, depending on your rig. Located just above oil filter
- Oil pan gasket - interfaces with front/rear cover gaskets
- Oil level sensor on the driver's side of the oil pan
- Oil drain plug

 

[John03Z71]

Last night after swapping out my O2 sensor I spent a little time trying to figure out where the oil leak(s) is coming from. I started the engine and crawled underneath for several minutes watching for drips. I found that there is an area above that O2 sensor (bank 1, sensor 1 - driver's side before cat) that is dripping down onto the exhaust, which is then causing a bit of smoke with each drop. (This would also explain why I smell burning oil coming from the air vents).
These aren't the best pics but do they, along with the description above, help anyone narrow down a potential source of the leak? Also I believe I have multiple leaks as when I park there are spots under the front and back of the engine... the spot under the back side is usually between the size of a softball and frisbee..

I'll try to get some more and better pics this weekend.
Thanks in advance for any help.

 

[JetBlackNali]

Oil cooler line? Metal to rubber fitting near front of block. On mine it was this fitting. At idle small drip but once the rpm increased a spray to the power steering pump area at front of block. Then blow back on highway and it took me a good week to find. Was covered all the way back to trans. Actually degreased and pressure washed the underside of engine. Dried and fired it up. Layed under there for 20 minutes and got a single drip. ????. Got the wife to rev it up and holy sh*t. There it was, a pinhole and a concentrated spray. These are known leakers. Metal expansion in the aluminum crimps. Another not so great design. (But it does make it easier to route when you have to change them). No brainer for me, aftermarket oil cooler and lines for me. 4 years and not a drop.

 

[retiredsparky]

Maybe you didn't see the posting about a clogged pcv valve. You can replace every oil related gasket on the engine, but if the pcv valve is clogged, pressure will build inside the crankcase and push oil past most of the seals on the engine.

The reason this happens is that as the engine ignites the gas/air mixture, some of the resulting high pressure gases are pushed past the piston rings into the crankcase. The pcv valve vents these gases into the intake of the engine and relieves that crankcase pressure if it is working properly.

 

[John03Z71]

Maybe you didn't see the posting about a clogged pcv valve. You can replace every oil related gasket on the engine, but if the pcv valve is clogged, pressure will build inside the crankcase and push oil past most of the seals on the engine.

The reason this happens is that as the engine ignites the gas/air mixture, some of the resulting high pressure gases are pushed past the piston rings into the crankcase. The pcv valve vents these gases into the intake of the engine and relieves that crankcase pressure if it is working properly.

Thanks for this suggestion (and the previous). I checked the PCV valve today and the bottom side of the fat end (facing down into valve cover) had a very thick layer of hard residue buildup that was definitely blocking the hole, it was caked on so thick that when I sat it down on the ground it tipped over because the bottom surface was rounded due to the buildup and no longer flat.

Haven’t had any idle or misfiring issues though. Popped the new one in and am keeping my fingers crossed. I don’t expect it will magically stop all my oil leaks, but even if it slows down a bit I would be happy... we’ll see. Thanks again for the input.

 

[mattt]

Did yours have a removable PCV valve? Most in this generation just have a fixed orifice in the valve cover that acts like a PCV valve. Did you remove the valve cover to check it?

 

[John03Z71]

Did yours have a removable PCV valve? Most in this generation just have a fixed orifice in the valve cover that acts like a PCV valve. Did you remove the valve cover to check it?

Yes I just pulled the vacuum hose off the valve cover (drivers side rear of engine). The PCV valve is in the end of that hose. I was able to pull the old one off with just my hands and a little elbow grease... put the new one in, then popped the hose w/ new PCV valve back in the top of the valve cover.

 

[yukonxlv]

Found plugged PCV system on high mileage 02 Yukon while chasing after similar leaks. A plugged crankcase venting system will start leaking oil even in places that not typically under pressure. The 02 original driver side valve cover was caked with carbon in the vented area inside the valve cover. At that time GM had a 3rd design valve cover available with much improved venting and built in PCV valve. Also needed a longer hose. How does the inside of your vent system for the valve cover look?