: Real bad oil leak!

03-08-13, 07:28 AM
Hey folks,

Looking for some opinions/help here. I just purchased a 1994 Seville SLS with 64,000 miles on the odometer. I looked the car over very well upon purchase, or at least I though I did. Car has absolutely no rust paint is immaculate, interior is a 9.5/10 and it has a Vogue top that is perfect. Everything about the car as it appears reinforced the claim that this was an older gentleman's car that was driven to church on Sundays and garage kept all its life. I was stoked when I bought it. Runs great, shifts like a dream doesn't overheat and when I bought it there was NO OIL LEAKS at all. I've been into cars as a hobby for years so I'm pretty well versed on the normal stuff but I'm a small block Chevy guy. This is my first low miles Northstar.

So I get the car home - about a 100 mile drive. Park the car in the garage. When I bought it the ABS light was on and it kept saying to check the oil even though the oil level was fine as I checked it right before the purchase.

The ABS issue ended up being a disconnected speed sensor - plugged it in and all was good.

Car sat overnight, I came out in the morning and the garage floor was clean - not a drop. I was pleased but my luck changed.

I took the car on another 100+ mile trip. Drove like a dream...upon my return I parked the car in the driveway. Next morning took it to work. When I left my wife called me and said that there was a 3inch puddle of oil under where the car was parked.


I drove the car home and put it in the garage. Next morning a fairly large puddle of oil was on the floor. I have other vehicles so I just left it parked till yesterday. I bought the oil level sender and upon looking under the car noticed that the oil pressure sender was leaking out of the plug. Seen this a lot on various GM cars, no prob - great! Found the source of the leak I thought to myself.

I replace the two senders and refill the oil. Start the car and let it idle. After about 2 minutes I start seeing oil dripping off he pan.

Drove her back on the ramps and cleaned everything real good with brake cleaner...and started her up.

Damn - You can watch the oil literally run down the pan and drip on the floor while that car is idling. It appeared to be coming from the pan gasket seal but it was weird because it would start running on the passenger side front (side toward the front of the car) of the pan first then steadily progress all the way across the front of the pan. Did not notice any oil above the oil pan.

So now I'm trying to figure out my leak. It seems to be a pressure leak. I have researched the forum and see that's an issue on these cars. Could it be that the oil cooler lines are leaking and its running down to the oil pan seam then wicking across? I've never seen an oil pan gasket leak so bad before. What do you guys think. I didn't know there were oil cooler lines till this morning and if I read right they are on the passenger side of the engine. What are my chances that the oil cooler lines are leaking and not the pan gasket? Dread having to pull the tranny to fix this but as it is now the leak is bad enough to where I will not drive the car. And it happed so fast - over a 3 day period.

Opinions and suggestions are welcome.

03-08-13, 10:06 AM
Does the leak appear to begin near the oil filter adapter/pressure sending switch area ?? If so, yours would not be the first to have a loose oil filter adapter. 2 bolts, 2 O-rings.

That ^^^ would be a pressure leak - the halfcase seal would also, but not the oil pan seal. ......... and these are not "gaskets" in the tradional sense - they are formed silicone "O-rings" set into machined grooves in the pan and halfcase flanges. The block, halfcase (lower block/stud girdle) and oil pan are all structural parts - flat flange bolted together - and the pan bolts have a specific torque and sequence just like a metal intake manifold in a SBC.

Go into my two albums and look for the engine drawings and the oil pan with oil in it. The "Community" tab, Albums, the red Seville.

Your transmission question - is the "oil" red or engine oil ??? transmission cooler lines in the driver's end radiator tank; engine oil cooler lines (if fitted with HD cooling option) run from the filter adapter top around into the front of the passenger side radiator end tank.

03-08-13, 12:27 PM
Its without a doubt engine oil. I do not see any up above the oil pan gasket but you can't really see that good around the oil filter adapter. I'm going to do a more through inspection today after work.

03-08-13, 12:42 PM
You MIGHT get away with simply tightening the oil filter adapter mounting bolts - 2 @ 12 lb/ft.

PITA, but drop the lower air deflector = 11 or 13 plastic pop rivets - pull out the center pin, the rivet collapses. Replacement rivets (and all sorts of pop fasteners) on the Help! racks at parts stores or $8.50 a box of 25 at a Fastenal store. http://www.fastenal.com/web/locations.ex?action=search&zip=&state=ON


scott f
03-08-13, 05:05 PM
The '94 doesn't have the new improved air deflector, is merely rubber matting type stuff. You'll have to jack the car up and reach up in there.. not a whole helluva lotta room but it can be done

03-09-13, 06:11 AM
Thanks. I picked up the oil adapter o rings yesterday. Gonna change them today and see what happens. I'll keep you all posted. Thanls for the replies!

03-09-13, 11:02 PM
Thanks. I picked up the oil adapter o rings yesterday. Gonna change them today and see what happens. I'll keep you all posted. Thanls for the replies! Please do. I have a '97 ETC with 64k o the ticker and I've been trying to find the oil leak for some time now. At first I thought it was the oil pressure sending unit and then the oil filter. I tye wrapped oil absorbent material around both and they are as dry as the day I put them on. I'm now thinking it may be the adapter "O" rings. I'll likely put it up for sale in the very near future and don't want to sell a car that's in like new condition with an oil leak.

03-11-13, 06:54 AM
Ok so I got a chance to look at her this weekend. I replaced the oil presure sender, the oil level sender and the oil adapter o-rings. No such luck. It's the dang pan gasket! Hard to believe that a 64000 mile northstar would leak from the pan so bad with so little miles. Sooo, got a GM shop manual, and engine support the gasket and 2 cases of beer on order. LOL I'm going to pull the tranny to get at the pan gasket. I haven't seen anyone document the procedure on here so I'll do that as I go along. Seems like it may be a 2 day project. A lot of work for a 14 dollar part!

03-11-13, 07:26 AM
Low mileage is one thing, but the car is 19 years old. Gaskets age.

Good luck with the job.

03-11-13, 08:51 AM
I understand. I have a 89 Cavi Convertable that don't leak a drop. Go figure...

03-11-13, 09:28 AM
You really are in the wrong forum for this depth of engine work - You NEED to go through at least the first page of threads down in Northstar Performance.

The procedure is documented in several threads - Northstar Performance (engine work) and Cadillac Tech Tips (everything nder the sun). There's an ongoing Northstar overhaul thread by daveyhouse that is current as of last evening.

The engine has to come out of the car in order to remove the oil pan. Instead of the superseded seal you can perform the new GM recommended oil pan seal replacement.

03-12-13, 10:39 AM
The trans comes out and motor bottom can be removed with motor in car. Still a whole bunch of work.

03-12-13, 11:08 AM
Cool thanks. And no the motor does not have to come out. You can remove the transmission to perform the repair. It's documented in my 99 Eldorado GM shop manual. Pretty much same procedure. Thanks for the heads up on the other forum posts.