Some history first, I had oil leaks in almost every top part of the engine. I changed, the cam cover gasket, cam oil seals and I put instant gasket on the cover edges for better sealing. That was sufficient for a while a month or so...Then, after I push the car a little bit more than usual above 4k rpm, it started leaking again. Another clue might be that the leak started after I change oil and oil filter, however I can't figure it out how those might connect.

So far, I've checked how much is the engine blowby. I checked all the solenoids for the PCV and breather valves. All of them look fine, also the engine doesn't burn oil. Soon I'm gonna do a compression test for extra evidence.

Ideally I would like to find what exactly is causing this leak before I change anything again.

Does anyone have any clue on what might be wrong here?

Thank you...

  • Is it leaking in all the same places it leaked previously? What is the mileage of the MX5? You said Mk1 ... but which year exactly? Are you sure you put the cam seals in correctly? No damage to them upon insertion? Completely square? No damage to where it rides on the cam? Any evidence of wear on the cam where the seal rides? Commented Sep 3, 2016 at 1:02
  • 3
    If you have access to an oil pressure gauge, I'd hook that up to see oil pressure at idle and 3500 rpm or so. If the oil got very dirty at one point you may have a malfuntioning bypass in the pump assembly. I found this nugget (I know your car is newer, but I doubt the pressures have changed much) "1990 Miata, the specified oil pump relief pressure is 50 - 64 psi, whereas the normal operating oil pressures are 28 - 43 psi at 1000 rpm and 43 - 57 psi at 3000 rpm. " Not an answer, but might eliminate a whole avenue of thought. Along with that, is the filter fresh?
    – SteveRacer
    Commented Sep 3, 2016 at 5:09
  • Paulster2: It does leak at the same places as before. The seals were fitted correctly and no damage to them or on the cam. When I removed the old seals where fitted firmly. SteveRacer: I used the pressure gauge on the dash to check if the pressure is correct and it does meet the specifications. But there is something that I'm not quite sure here. When I step on it, on warm engine, and pass the 4k rpm, the pressure can reach up to 6 kg/cm2, is that normal or indicates a malfunctioning oil bypass valve?
    – Alimba
    Commented Sep 3, 2016 at 12:35
  • 2
    @Alimba Heck yes, or at least I think so. Gave this Yankee a bit of a headache, but [I think] 6 kgf/cm^2 works out to 85 psi. Which is way too much, anywhere, anyhow. But let's get somebody with more experience with that conversion to chime in before you panic. If there was a metric to understand my understanding of metric, you'd understand that I don't understand metric...
    – SteveRacer
    Commented Sep 3, 2016 at 23:49
  • @SteveRacer Yes, you are correct about the conversion of the units. So, there is one question remain, what is causing the pressure to keep rising after the 3k rpm? and how to fix it?
    – Alimba
    Commented Sep 4, 2016 at 11:14

1 Answer 1


I opened the engine again, and found out that it wasn't leaking from the camshaft this time, but from the crankshaft. That was the only thing that I didn't replace in the first place.

So, the advice here is, when you start replacing gaskets and seals of a system, replace all the involving gaskets and seals.

I hope that will help someone with similar issues.

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