Elusive Oil Leak

[pcmos]

I have a strange oil leak on my 2004 LeSabre. There is oil all over the bottom and driver's side of the oil pan. Initially I suspected I had a rear main seal leak because it seemed to be coming from behind the flex plate. After removing the plastic cover though, it seems to be completely dry on the flex plate and torque converter. Not even any residue to indicate oil being flung off of those components.

My next attempt to fix the problem was to completely remove the oil pan and gasket. I thoroughly scrubbed the pan and related components. I then applied RTV and a new gasket and re-sealed the pan. Additionally I replaced the drain plug and level sensor o-ring.

For a long time the pan seemed to remain dry, until a few weeks ago when I noticed it was covered in oil again. This time I replaced both front and rear valve cover gaskets and even applied RTV to ensure a really tight seal. Once again I scrubbed the oil pan with dish soap to get it really dry and clean.

Given a couple weeks of driving, I've got oil all over the pan again. I'm really frustrated by this, I had the exact same problem on my 2000 LeSabre but never had a chance to figure it out before trading the car. Aside from a lower intake seal leak, where else could this oil be coming from?? I know it has to be leaking from above the pan because after cleaning the pan, the pan seal, level seal, plug and oil filter all remain clean and dry for a long time. The oil is coming from someplace higher up on the engine and I've already ruled out valve cover leaks.

We're not talking about a major leak, but just enough to leave a residue on the pan and a few small drips on the lowest parts of the engine. Over the course of an oil change I seem to lose about a quart and a half. I'm convinced a significant portion of that loss is probably due to this small external leak someplace. I want to track it down and fix it. My fear is that the leak will become progressively worse, or that it is indicative of a more serious problem.

[auto trainy]

Dealers and good repair shops use an additive in the fluids (oil,coolant,freon,ect) and after a few miles of driving check with a black light to see where the leaks are with little guess work you might want to check that out. Good Luck

[HotZ28]

I think you may have the typical leak on the end seals of the LIM and it is draining down the block to the oil pan. As long as you don’t have oil dripping on your driveway, or garage floor, it is nothing to worry about. If you want an idea of how 1-drop of oil can spread on smooth metal, take an eyedropper and place 1-drop of engine oil on a 1-ft dia smooth metal sample and let it spread while sitting horizontally, then flip the sample to the vertical position and put a fan in front. Let it sit overnight with the fan blowing to simulate air blowing under your car while driving. I think you will be amazed to see how 1-drop can spread. If you were leaking ½ qt between changes, you would see large oil spots in your usual parking spot. You sound a lot like me, when noting is broken, we are looking for something else to fix! I like my car to be prefect also, but a little oil residue on the bottom of the oil pan would not concern me.

[pcmos]

I totally understand what you are saying. I just think it may be the case that my leak is worse than a few drops spread over the pan. I park on blacktop at an apartment complex with no assigned parking spaces. It's really difficult for me to gauge whether or not I'm leaving droplets on the pavement overnight. When I crawl under the car I basically have drips on every sharp edge or corner. After scrubbing the pan again yesterday, I see today it's already completely covered in oil again. I think we may all be underestimating how much loss this leak is causing.

When I had my 2000 I basically ignored the problem, aside from replacing the pan gasket and valve cover gaskets I didn't really bother with it. I had the same typical oil loss on that car that I have on this car now. I want to pinpoint the source and see what happens with the oil "consumption" issue when I can keep the block and pan dry for more than a day. I'm starting to think the "consumption" issue is going to drastically improve.

The leak itself looks very innocent because as you say there isn't more than a residue and a couple droplets, but I've now proven that those droplets reappear only a day after scrubbing them off. I drove the car about 25 miles and its already covered in oil again.

I'm planning a cross country drive pretty soon so I'll probably put off any major maintanance on the LIM until after I do my trip. Fortunately I have a brand new LIM and gaskets that I purchased for my 2000 before trading the car. I'll probably install the new LIM and a brand new UIM as well and take extra care to ensure a good seal with RTV.

I really can't think of another likely leak source besides the LIM gaskets, assuming the crank seals are tight.

[HotZ28]

Originally Posted by pcmos

I think we may all be underestimating how much loss this leak is causing.

You might try putting a clean piece of cardboard under the oil pan soon after you park it to see if you have any oil dropping on that. BTW, just out of curiosity, have you checked the PCV & O-rings on this engine?

[pcmos]

I haven't specifically checked the PCV valve recently. It's certainly a good idea to keep the PCV and o-rings in good shape, but I don't think that could lead to the sort of external leak I have.

I'm fairly sure its leaving small droplets whenever I park it someplace. I really think the leak is causing my so-called "consumption". I never had any "consumption" until this external leak started.

[HotZ28]

The reason I mentioned the PCV was if you have an oil leak, the first thing you should do is to make sure the PCV system is working properly.

The typical signs of PCV valve failure are:

1. The engine may run rough, or stall.
2. The engine uses more oil than normal.
3. There is (or not) some smoke from the exhaust.
4. The engine is using more oil than normal & oil puddles form under the car when parked.

The PCV helps to maintain a neutral pressure, or slightly negative on the crankcase. If the pressure becomes positive, this can cause oil leakage at gaskets/seals which may not otherwise leak.

[pcmos]

Yeah its a good point that you raise. I'll probably just replace it tomorrow when i can stop by a dealer at lunchtime and pick up another one.

[pcmos]

Just to update... I went ahead and replaced the PCV valve. I also cleaned off the oil pan again. Unfortunately there is no real change in the leak. I've got oil all over the pan again. I really suspect the lower intake gaskets, especially at the end caps. It's going to be a while before I have a chance to replace those and get the LIM sealed.

[imidazol97]

Originally Posted by pcmos

Just to update... I went ahead and replaced the PCV valve. I also cleaned off the oil pan again. Unfortunately there is no real change in the leak. I've got oil all over the pan again. I really suspect the lower intake gaskets, especially at the end caps. It's going to be a while before I have a chance to replace those and get the LIM sealed.

In the interest of getting more information for the experts here to help suggest things...

What kind of oil are you using? If it's synthetic, do those oils tend to leak more?

When you say the 1.5 qt. of oil disappears over an oil change, is that 15,000 for synthetic? 3000 on regular oil? 6000 miles? What kind of driving? Is it short trip with lots of cold starts or high speed interstate type driving?

How many miles on the car?

Even 1.5 qt in 3000 miles is not considered a problem amount.

Have you checked the ends of the lower intake to see if there's any oil showing on top of the motor? I find a little puddle in a valley on top of my lower which I believe is oil wicking up the bolt threads. I dab it up with a paper towel on a screwdriver and go another 20K miles or so before I notice it.

[pcmos]

I only use Mobile 1 Extended Life full synthetic 5W-30 oil. I also use the high milage Fram Tough Guard filter.

In my opinion I'm not comfortable allowing an oil change interval to exceed 7000 miles. Typically I follow the built-in oil life indicator and change my oil when it gets down to 15%. In any event I would never allow the oil to go more than 7000 miles. Generally the oil life indicator ends up prompting me to change the oil after approximately 5000 miles of mixed highway / city driving.

Please understand that I'm not concerned about the oil "consumption" issue. You are correct, 1.5 quarts or so in 5000 miles is considered acceptable.

I'm concerned about ANY external oil leak. An engine should not be leaking oil either externally or internally. Oil "consumption" should only occur because of ring seepage or vaporization and chemical breakdown of the oil itself. I put the word "consumption" in quotes because its highly ambiguous. Nothing is ever "consumed" in an engine, it has to go someplace. I don't believe my engine is combusting 1.5 quarts of oil between changes.

Having droplets of oil or oil residue present anywhere on my engine is not acceptable to me in the least bit.

After taking all of these suggestions into consideration I do believe that the lower intake end cap seals are leaking. I don't see oil pooling in the recess around the injector ports as you suggested. When I replace the lower intake in a couple months I'm going to apply sealant to all of the bolt threads in order to gauruntee that oil won't be able to "wick" up the threads.

Based on my experiences I'm postulating something that is somewhat controversial. My theory is that when I resolve the external oil leaks I will not lose even 1.5 quarts of oil between changes. I firmly believe that what people experience on these cars as "consumption" is actually mostly due to external leakage. I believe your oil residue on your lower intake is actually amounting to a loss of approximately 1.5 quarts per oil change interval.

I can back up my claim by pointing to the fact that when I scrub my oil pan clean and drive the car for about 150 or 200 miles it becomes covered in oil again. Despite what looks like an insignificant leak, I believe that whatever is causing this external leak is actually quite signifcant and amounting to at least a quart of oil loss between oil changes.

My goal is to determine what the external leak actually is and then to solve it and watch my oil "consumption" after completing the repair.

Bottom line.... when my oil pan remains entirely dry for 5000 miles, my engine will no longer "consume" oil. In my opinion.

[danshot]

Did you ever solve your leak problem? Sounds like the leak I have on my 95. It's just kinda bothersome. Funny how the engine doesn't seem to be wet above the oil pan. I was thinking oil pan gasket, but after reading your post, I'm rethinking.

[pcmos]

I'm virtually 100% convinced that my leak is either the rear main seal or the rear main seal housing gasket. In any event the transmission would have to be pulled and half the engine bay would have to be disassembled including the flywheel to find out for sure. Since the leak isn't exactly niagara falls, I'm going to leave it alone. I really wish now that when I had the same problem on my 2000 I had pulled the flywheel to fully inspect that area during my transmission rebuild project. At the time I really didn't feel like adding another job to my already long list.

I can certainly say though that when / if I ever replace those seals I'm going to apply a very thin coat of RTV to virtually everything, including the press fit rear main seal. I've never had good luck pressing new seals into anything without resultant seapage and tiny leaks. The manuals don't mention applying anything to the press fit seals, they instruct the technician to press them totally dry. My experience tells me that they hardly ever seal perfectly the second time.

[danshot]

Not sure if mine is the rear main, but 100% sure is pretty sure. I'm with you. I think I'll just watch it for a while. Mine uses about a quart between changes (3-5K). Seems like it might just be better to pull the whole engine than bend over and disassemble half of it. At least that way you get a good visual of where it is originating from.

[pcmos]

Yeah I can't say 100% outright, but "virtually" 100% because it's just so difficult to be sure without actually looking at it. I just don't see any evidence of significant seapage from the lower intake gaskets or valve covers on mine.

I've done the transmission removal on the 2000 and I really think it was easier to pull the tranny versus the engine. When I did the transmission project I built a frame that rests on the fenders and strut towers. I had the car up about 16 inches. I hung some chains and hooks from the frame and transferred the load of the engine to the front clip. Once the engine is suspended, the sub frame can be dropped down. Transmission comes out from the bottom relatively easily. I'm just glad I didn't have to do all the fuel line and sensor connections for the motor. The engine is also frustrating to remove because you have to figure out a way to deal with the A/C refrigerant system.

What I can say for sure though is that if you remove the transmission with the car jacked up high enough to get the tranny out from below, there is easy access to the rear main seal and flywheel area. It wouldn't be much of a challenge to do the engine seals with the transmission pulled. The transmission removal procedure gets so much out of your way anyhow.

I've never removed an engine from a LeSabre so I can't really speak to the difficulty of that. I'd be sort of curious to hear from someone who has done it a couple times.