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Potential route cause of this black oil film

23 May 2024
Hi all,
I am so glad to join the NSX prime after admiring the NSX for a long time. I am from U.K., own a 911sc, imported from JDM.

I am also looking for a NSX and has located one potential car. However after looking around the underneath, in one particular area, I can see a thick layer of black oil/dirt film (right side of the exhaust pipes on the first photo). I am not too sure the root cause of this as this is quite close to the gearbox/drive shafts area. It may also be caused by oil weeping from the gearbox-engine joint?

Can anyone shed some lights on this?
Many thanks,


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Hi Justin- welcome to NSX Prime!

The oil leak you're seeing is fairly typical for a NSX that is lacking regular maintenance. The culprits in order of commonality are:
  • Valve cover gaskets (most common). Most service techs pinch them during install and the oil runs down the entire engine block.
  • Camshaft caps. These will start to weep oil after about 5-7 years. Sooner if the car was tracked heavily.
  • Spool valve gaskets. Less common, but can really leak badly since they seal full oil pressure.
  • Oil pressure sender O-ring. This can fail and cause a slow, weeping leak. Not common though.
Based on the amount of oil on the bottom of the engine block, I'd bet it's the valve cover gaskets.
Awesome @Honcho for this quick diagnosis! At least I know it could be something more straightforward fix. Yes indeed the car has been sitting for few years with little driving.