Newell47

New to me 981. Has a small oil leak at drain plug which blows back on exhaust and gives me a burning oil smell. 3 shops have confirmed the leak. New plug and crush washer installed but still slight leak only when engine runs. No oil on the garage floor..
Suggestions???
Thanks in advance

981KMAN

What brand Drain Plug and Crush Washer? What Torque used to tighten Drain Plug?

Inspection of Drain Hole in Engine Pan for damage? Pictures?

The aluminum crush washer is key to seal the drain hole, they cost about 25 Cents when purchased from Pelican Parts. Ensure that it is the proper thickness (1.5mm) prior to use and that it truly is a virgin washer.

ICNU

Something doesnt make sense. There is a lot of real estate (about 3ft/1M) and stuff in between the oil drain plug and the exhaust. I dont see how a tiny leak at the drain plug would ever manage to blow all the way back on the exhaust and not drip on the floor after driving? There would be signs of oil splattered everywhere on the parts in between the plug and exhaust for this to happen.

Are you sure its not coming from the oil filter canister or some other part of the car instead? The filter canister is a little closer to the back of the car than the oil drain plug is, and its up higher in the chassis where leaks can end up puddling up on top of chassis braces and other parts of the car vs the drain plug which will drip right down onto the floor.

There is also a gear oil drain plug that looks like the engine oil drain plug on the transmission bottom that is directly above the triangle brace next to the exhaust, and any leak there could easily puddle up on the brace top and then work its way towards the exhaust when driving. Any leak from there would also look like motor oil

STS79

Maybe your air/oil separator is bad? I wouldn't think the drain plug would only leak on the exhaust when running.

Newell47

Drain plug and washer were installed from OEM Porsche and torqued to spec. Later mechanic tightened iit a 1/8 turn more

Newell47

All goof points.

Oil filter was cleaned and has stayed dry. Soul track exhaust installed so perhaps exhaust is closer .
Is there anything on top that could leak doen to exhaust?

Car was tracked. maybe oil pan bottomed hard and cracked, but none apparent. Dye was put in oil and infra red only showed up on oil pan

ICNU

Aftermarket exhaust sits no closer to the oil drain plug than factory. There is nothing above the exhaust other than the bumper cover, so this is why I said it seems odd that such a small leak could possibly ever make it all the way back onto the exhaust without you seeing oil splattered everywhere on the underside of the car?

IndigoInkTaco

Yea agreed, seems like oil drain plug would be leaking when parked and not driven when more oil is present in the pan and not dispersed through the motor while driving.

okie981

If this is true, it's possible the drain plug was OVER torqued. The OEM torque spec is higher than it needs to be to prevent leaks if a correct and new washer is used and all mating surfaces of the pan and the plug to the washer are smooth and clean (no burrs, gouges, etc.). The magnetic drain plug sold by LN Engineering (that I have used for around 15 oil drains) requires only 19 lb-ft of torque to seal without any leaks. I believe OEM spec is 38 lb-ft. So if torqued to 38 lb-ft and then adding another 45 degrees of rotation (1/8 turn) to the plug will result in an over torque situation. Those are aluminum threads in the pan and I believe the OEM plug is steel. Asking for trouble here by over torquing the plug.

Edit: To remove any doubt, LN Engineering requires the 19 lb-ft of torque for their magnetic drain plug, I didn't make that number up. I believe LN Engineering knows a bit about Porsche engines and they designed the magnetic plug.

981KMAN

Porsche OEM Drain Plug is Aluminum....... Yes, if you over-torque the drain plug you can damage the threads on both the Pan and the Plug. Thus you need to use a accurate Torque Wrench.

I have used the Porsche drain plug torque specification of 37 Ft-Lbs (50NM) for many oil changes with no issues. If you use an Aftermarket Drain Plug that is not Aluminum, then you will probably use a different torque rating, yet I would not apply the Aftermarket Drain Plug torque specification to the OEM components.

Kitc2246

The dye fluoresces under ultraviolet, not infrared. It should clearly show the source of the leak. A leaking drain plug should be fairly obvious and would normally drip on the garage floor. As many have indicated it is too easy to damage the aluminum pan by over torqueing the steel drain plug. Sources above are normally the AOS or oil filter, which you seem to have eliminated. .Where on the oil pan was the oil? Check to see if the oil is leaking from the pan mounting bolts or gasket area.

okie981

Thanks. I removed my OEM plug the first time I did an oil drain in fall of 2015 and haven't seen it since, couldn't remember. I did the same for my GT4 that I bought new and sold it with the LN Engineering magnetic plug installed (to Rennlist member @ducsfly). I know for sure the LN Engineering magnetic plug is aluminum (all threads and mating surfaces) except for the magnetic insert on the inside.

okie981

While reading this topic of sealing washers for oil drain plugs, it reminded me of a critical material spec for such a washer and one that may not be correct for non-OEM aluminum sealing washers. I always buy mine from Porsche dealers via web orders. Not saying no other washers are made to the correct spec, I have no idea what other sellers offer. I can say I used a non-OEM seal washer one time with my LN Engineering plug and it seeped when torqued to LN's recommended 19 lb-ft of torque. Every time before and after I've used OEM seal washers and never had an issue at 19 lb-ft. This is across my experience of 15+ oil changes on my BS.

That critical spec is yield strength. The washer needs to be "soft" enough to allow permanent deformation at torque spec, but not too soft as to not provide proper sealing pressure or to deform further over time and heat exposure. If the minimum yield strength is too high for example, the washer will not deform at all during the compression to torque spec. Deformation provides a better seal between the surfaces, smooth and shiny as can be seen when the old seal washer is removed and inspected closely.

Of course, I could be all wrong.

981KMAN

@okie981 I agree with your thinking....

I use the OEM 37 Ft-Lb torque spec with the OEM Drain Plug & Crush Washer, yet I agree that it seems very tight. It works, and I have not had any issues,... yet I cringe a little each time I torque the plug after an oil change.
And thus a possible reason, of several, that Porsche went with the Plastic Drain Plug with rubber "O-ring" in the 991.2 & 982 cars......

okie981

Did not know that.....