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Small oil leak from front valve cover near oil fill cap

12 October 2015
Utica, NY
I've noticed that there is a small amount of what looks like engine oil in the area around the bolt nearest to the oil cap on the front valve cover. It appears to be a very small leak (as in I've never seen a spot under the car) however still something I want to remedy. I can't tell if the oil is coming up through the seal on that bolt or if it's actually coming out from the oil cap and simply making its way into that low spot where the bolt is. Anyone have any ideas or suggestions? Could it be something a simple as re-torquing that bolt, changing the seal, new oil cap etc? Any input is greatly appreciated as always.




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Clean and dry the area well. Drive the car for a couple of days and retrace the oil leak.

Have you added some oil recently?

I haven't added any oil recently, it was under the car cover from November until about 2 weeks ago when I took it out for just a couple short drives. I'll clean it up and keep an eye on it.
Check your PVC system to make sure that it is venting and not pressurizing the crankcase. If this is the only spot where it is wet I would 'normally' be inclined to just say weeping seal on the oil filler or failed seal on the bolt and just replace them to see if that fixes the problem. The seals are #22 and #14 in this diagram

Cylinder Head Cover for 2000 Acura NSX | OEM Parts Online

In a rather bizarre pricing mechanism, it is a nudge cheaper to purchase a new oil filler cap with seal than just the seal alone. Amayama sells just the seal for a reasonable price and even with shipping it is a lower cost than the seal from Acura US. Given the rather silly price for the seal from Acura US I would be inclined to make sure that the PVC system is not the problem before my 'normal' reflex of changing the seals. The seal under the nut is available from the aftermarket for a reasonable price.


Amayama's price for that seal is slightly better than Acura US; but, I would purchase locally unless you are also ordering the ring for the filler cap. Have a look around to see whether any other seals look dodgy. If you are ordering from Amayama, one piece of rubber that weighs nothing ships for about the same price as 5 or 6 pieces of rubber that weigh nothing.
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Thanks for the details [MENTION=26435]Old Guy[/MENTION]. How would I go about checking to make sure the crankcase is venting properly?
Referring to the service manual is probably your best solution. There are links to free versions of the early and late service manuals on Prime The service manual says to clamp the hose between the PCV valve and the intake manifold at idle and then listen for clicking from the valve. If the valve doesn't click, you have a problem someplace in the PCV system. If you are an Old Guy with Old Guy hearing the clicking can be hard to detect over the engine noise, especially if you have an aftermarket exhaust.

I have never done this on the NSX; but, at idle the PCV should draw a fairly good vacuum on the crankcase area. Clamp off the fresh air inlet for the PCV system and hold a piece of paper over the open oil filler opening and the vacuum should try to suck the paper down onto the opening. If it doesn't there is a problem with the PCV or you have serious blow by. Like I said, I have never tried this on the NSX; but, it works on other engines.