Pretty Bad oil leak on my 98 TA

**79JON** · 12-07-2008, 02:09 AM

Like my title reads, I have a pretty good oil leak on my 98 Trans Am. The car is my daily driver and has just over 161K miles. 2 weeks ago it was time for an oil change so I changed it with the Mobil 1 Synthetic 10W30/WIX filter like I always do. Everything seemed fine, I even drove a 200 mile trip right after the oil change and there was no leak. Well this past week im driving to work one day and I notice a burning oil smell and I look under my car and there is about a 4 or 5 inch puddle of oil on the ground and the whole underside of my car is covered in oil. My first thought was damn.. I either left the oil filter loose or the filter itself was faulty because this never happened before and it started after the oil change. Well my brother and I craw under it and the oil plug is nice and tight, and the filter is actually nice and dry and tight. The leak looks the be coming from between the the tranny and engine. So I was going to ask on here, Is it common for rear main seals go out on a LS1? And do you think thats probably what it is? My brother called a friend which is a mechanic and asked about it, and he said it might also be the oil pressure sending unit on the back of the motor. I was just going to come on here and ask what yall thought it might be according to my description of the leak.

Thanks,
Jon

**JoshieDoom** · 12-07-2008, 03:25 AM

Hopefully its just the sending unit. Had this happen a lot on early 90s models cavaliers in the shop. Reach back there and feel for oil.

**SteveC** · 12-07-2008, 04:22 AM

Originally Posted by 79JON

Like my title reads, I have a pretty good oil leak on my 98 Trans Am. The car is my daily driver and has just over 161K miles. 2 weeks ago it was time for an oil change so I changed it with the Mobil 1 Synthetic 10W30/WIX filter like I always do. Everything seemed fine, I even drove a 200 mile trip right after the oil change and there was no leak. Well this past week im driving to work one day and I notice a burning oil smell and I look under my car and there is about a 4 or 5 inch puddle of oil on the ground and the whole underside of my car is covered in oil. My first thought was damn.. I either left the oil filter loose or the filter itself was faulty because this never happened before and it started after the oil change. Well my brother and I craw under it and the oil plug is nice and tight, and the filter is actually nice and dry and tight. The leak looks the be coming from between the the tranny and engine. So I was going to ask on here, Is it common for rear main seals go out on a LS1? And do you think thats probably what it is? My brother called a friend which is a mechanic and asked about it, and he said it might also be the oil pressure sending unit on the back of the motor. I was just going to come on here and ask what yall thought it might be according to my description of the leak.

Thanks,
Jon

The rear main seals on GM cars are infamous leakers, usually they "sweat", however at that milage, it is a constant. It is probably time to replace it.

The aftermarket seals (felpro) probably are a better quality.

SteveC

**bills98ta** · 12-07-2008, 06:22 AM

If it is the main, it's a lot easier to replace. Drop the tranny, pull the flywheel, and it looks like the front timing cover with a one piece seal that unbolts right off. Might be able to look behind the intake with a mirror to check the oil sender. Good Luck !

**Banshee1967** · 12-08-2008, 01:02 PM

Don't mean to sound simple and use simplicity..

161k on engine, changes oil 2 weeks ago, takes on a trip..no problem.

Has oil on back of motor and trans, smells burning oil. Is it a smell of oil burning off of a manifold or of burnt oil? With only say 300 miles on the oil change, the smell, without say contact on a manifold would be weak. A 4 to 5" puddle is a huge leap on a rear main. They are usually gradual..dime, quarter size to start.. Not 4-5" which would be rather extreme for a beginning leak, but not impossible.

I say there is a problem with the oil filter. Not tight, gasket not seated/sealing, old gasket still on block.

Seems too coincidentl that a rear main would go out within 2 weeks of an oil change. I would check the filter first.

My 97 T/A did the same thing...a week later. smoking like a SOB. Didn't get the old gasket off. As well, if gasket not lubed, the filter can back off.

**sunsetorangess** · 12-10-2008, 01:16 AM

Flush/Wash the area with water and some degreaser, get the car up in the air and secure with jackstands, then start it up and see if you can pinpoint a leak befor assuming its the worst. Could be a bad seal at the oil filter, a pin hole in the filter etc etc. Was the drain plug dry?
Not to insult you but did you remove the old oil filter gasket? Personaly iv been working on cars for about 9 years and never had a problem, then three months ago i actualy left the old gasket on the housing, Ran for a few days then all of a sudden i had about a quart of oil under my truck. It happens.

J

**79JON** · 12-10-2008, 02:39 AM

Well.. that was my first thought, that it was the oil filter or the old gasket may have stayed on it while the new one was put on. But when we crawled up under it and had it running the filter was dry not leaking any. It looked to come straight beneath and on the passenger side. So I took it to the shop and they said my oil pan was leaking and the rear main seal was leaking. I just dont see how all this can go out at once though.. The car never leaked any not even a slow drop here and there. My guess is the shop saw that the oil pan was leaking in a few spots and so they will replace that and while they are there they will replace the rear main seal.