-=Tom=-

Hey guys so I went out to change the oil on my car to get ready for spring and after sitting all winter in my garage with a cover, I see it's developed an oil leak near the rear of the engine. I cannot for the life of me see where the leak is coming from. The top of the engine from the rear is dry as can be. The rear of the intake manifold is also dry as I previously had a leaky manifold a couple years back that's been fixed so I knew to check there.

I got underneath and looked and it appears as though the driver side of the oil pan might have some oily cables there making me think the leak came down the side of the block there but there's nothing there. The cables just seem oily, nothing extra. It could be leaking from the oil pan gasket maybe? That's my current suspicion but leaking from the back of the gasket as the oil drops from the car at the flywheel cover. Not a lot but enough that I can see a drop hanging from there and there's more on the garage floor than I'd like.

I'm going to buy some ramps this week so I can really get under there and have more breathing room to poke around. With the floor jack and stands it's cramped under there for me to reach up anywhere to feel around.

Any thoughts from any of you guys?

Thanks in advance for any suggestions.

STL94LT1

If not the intake. How about valve covers, oil pressure sensor, oil temp sensor, oil level sensor, oil pan, oil filter adapter?

ninetyfivevette

Do you have Harbor Freight in Ontario? I'm sure you've got something similar if not.

You might consider a pair of 6 ton jack stands- those will give you some great working room- at least 6" more than a standard set of ramps. I've got both myself- I drive the rear onto the ramps and use a pair of jacks to lift the front so I can get the car in the air in about 5 minutes. I sure miss my 4 post lift!

joesgulfstream

I hope you put stands under the front ?

-=Tom=-

It's not the valve covers, that was my first guess. They're dry all around.

I can't get out to the garage until after work on Tuesday and look at the oil filter adapter and related oil sensors.

Thanks so far for the suggestions guys.

ks5shooter

[QUOTE=-=Tom=-;1573419749]It's not the valve covers, that was my first guess. They're dry all around.

related oil sensors.

The usual culprits

-=Tom=-

I'm starting to think after looking at my FSM that you guys might be onto something with the related oil sensors. I didn't even know they were over there like that and after reading my FSM that might explain why the wiring on that side has wet oil on it and it trickles down to the flywheel cover and then onto the floor.

I sincerely hope this is it as I wasn't looking forward to a pan gasket replacement but would've done it as I can't stand my car having any leaks.

Thanks guys as I never would've considered that avenue as obvious as it seems.

Anyways I rearranged my plans for tomorrow to Tuesday and will get under the car tomorrow night for a closer inspection of the sensors and post back here with my findings.

ks5shooter

Dont get under the car they(oil sensors) are at the top of the motor at the back,look under the EGR,if thats it you will see it,use a flashlight

STL94LT1

The oil temp sensor is in the block just above the oil filter, the oil pressure sensor is on top at the back of the block, and the oil level sensor is in the oil pan. So to check them all, he will need to get under the car.

Also recently a few guys have had oil filter adapter leaks, I would check that while under the car.

-=Tom=-

Thanks I will check the filter adapter for leaks while under there. Since I just put a new filter on and haven't run the engine yet I'll be able to pull it off without spilling any oil.

My FSM for my 95 says all of those sensors are down near the filter in the oil filter housing (other than the oil level sensor) and none up by the top of the block though. I'm guessing earlier years had the pressure sensor in a different location than my 95 because both of you guys said it's up top. Regardless I'll check them all out tomorrow after work.

Thanks again for the advice, I appreciate it.

-=Tom=-

Hey guys just an update. I spent the last couple of hours looking for the leak and can't see any. I wiped everything clean and put a piece of cardboard under the car to see if it leaks further in the next two weeks before its back on the road.

By the way there's an error in my FSM. It clearly shows the oil pressure sensor on the oil filter housing but lo and behold it's up near the top where you guys said. I double and triple checked the FSM and the diagram and it's clearly marked. That's odd.

Regardless I'm going to leave it sit and see. The oil pan gasket doesn't show any significant leaking although it looks wetter than it should all around. I wonder if it could weep?

Anyways none of the sensors had any signs of leaks, the filter adapter neither. I'm sincerely hoping the oil might've been spilled when I changed the oil prior to storing it although I don't remember spilling any. At this point I'll wait and see. I'll post back here eventually to update the thread for anyone that might look at this in the future.

-=Tom=-

Bah, tomorrow's the day the car is back on the road and I look underneath at the cardboard I put there and there's more oil. Now I've got to get underneath again tonight to see if I can pinpoint the leak since I wiped it all down a couple weeks back. This is extremely frustrating in trying to locate the leak.

On another note, does anyone have any insight to how hard it is to change the oil pan gasket? It just seems 'dirty' all around and doesn't look like it would hurt to change it. It doesn't seem difficult but I'll look in my FSM tonight. Just curious if anyone has done it and if it was hard or not?

Thanks.

Pete K

They sell dye and blacklight kits that may help. The dye is poured into the oil, engine is run, and you use a blacklight to see the luminescent trail back to the point of origin. You may want to consider purchasing one to minimize your aggravation.

WW7

Don't rule out it being a Rear Main Seal.. I have seen these leak on cars that aren't run often..This could also be why you don't actually see the leak, the rear main is behind the metel inspection pan on the bottom of the motor.Also you mention a error in your FSM, are you sure the manual says the sensor over the oil filter is the (Oil pressure sensor) and not the (Oil temp sensor)???.WW

-=Tom=-

Yes it's clear in the FSM and there's even a picture there. It shows the pressure and temp sensor as being down on the oil filter housing. It is indeed a mistake, I might scan in the page later on so you know I'm not making it up.

As for the light and dye trick I saw that in my FSM but wasn't really sure where to get that and I want it to be my last resort but I'm almost there.

WW do you know how hard is it to replace the rear main seal? I had a suspicion it may be that but as you said, I can't see it. I tried looking in my FSM for that and can't locate what it's called or the section in the FSM. I'm going to remove the inspection pan if I can tonight and look up in there. I definitely don't drive it much, I think 3000 km in the last 2 years.

WW7

Tom, I wasn't saying I didn't believe you, I just thought maybe you misread what was there, I have also found mistakes in the FSM on things like Torque specs.. On my 89 I had to pull the transmission out to get to the rear main , once thats out it was very simple to remove the flex plate and tap in a new seal .. Im not sure on your 95 if its exactly the same, hopefully someone with a LT1 will chime in and let you know. The idea Pete K had about using the dye is a good one if you pull the inspection plate on the bottom and can't tell if thats the problem or not..Most of the time though you can see the oil that has run down from the rear main..Good Luck..WW

-=Tom=-

No harm done, I was just kidding about not believing me.

I've got a 6-speed as well so I'm not sure how that impacts changing the seal. I'll try to take the cover off tonight from underneath and see what's there.

WW7

The Clutch and pressure plate are a little more work then my flexplate was to take off but it shouldn't take to much longer..Im hoping its not your rear main and is something easier to fix... .WW

-=Tom=-

Yay, I solved the leak and it only cost 3.00 and some change. Unbelievably it was the washer on the oil drain plug itself! I'm so happy it was something relatively simple but feel like an idiot that I couldn't figure it out for the longest time.

I couldn't see where the leak was, and wiped everything down super clean. Then I put some cardboard underneath the car and left it and came back a couple weeks later and saw the leak again on the ground but I still couldn't tell where it was coming from. I thought it was weeping from the drain plug since after I wiped everything down dry and clean that was the only place that was wet but still no drips off it and dry above the drain plug. I look in my FSM and see there's supposed to be a washer on the drain plug and don't remember seeing one on it when I changed the oil before storing it for the winter. I go to the GM dealer and buy three of them just to have spares. I pull off the drain plug and there is indeed a plastic crush washer. I assume it's been crushed over and over because I couldn't get the darned thing off the drain plug. I put the new metal one with the rubber middle on and screw it back in and re-fill the oil and leave it overnight with paper underneath and no leaks!!!!

Sorry for the long post but I'm really happy that my car doesn't leak anymore and it was an easier repair than I thought it would turn out to be. I also like to post resolutions to tech threads in case anyone checks it in the future.

Thanks for all of the advice guys, this forum is awesome as usual.

Have a Happy Easter!

STL94LT1

Glad to see it was an easy fix, so easy none of even mentioned the oil drain plug.