Oil leak from back of valve cover

[— Agent☣Orange —]

My buddy Joe had a pretty bad leak on his 2001 VVT so we checked out the usual suspect: rear of valve cover and sure enough, the plastic cap was allowing a pretty good flow to seep out, find its way down the head and end up dripping from the tranny. This is pretty common with older Miata motors. The oil drain plug was dry so it was easy to see that wasn't it.

Pulled the Miata up on the ramps


Joe had just replaced his valve cover gasket but the leak was coming from the plastic cap that sits under the separate exhaust cam journal. Access to it requires removal of the valve cover


Problem part


Fixed


Just about done


Then a little diagnostics since we were curious about vacuum, timing and O2 sensors

[—RuckkehrMiata—]

Forgive my ignorance, is that car ODBII or I? Have been thinking of getting a tool/app like that but haven't seen anything impressive for my `92

[— Agent☣Orange —]

Sorry man, it's OBD II (1996+)

[atlnb]

Very useful post. Thanks!

[—RuckkehrMiata—]

Maybe I should just bite the bullet and do a 1.8 swap so I can have OBDII

Sorry man, it's OBD II (1996+)

[—RotorNutFD3S—]

Good info! I also just swapped this part out over the weekend as mine was seeping quite a bit. I ordered the replacement cap from Mazda (they supposedly have changed the design and the part has a thicker gasket material) and did it without removing the valve cover. It was a matter of loosening the valve cover just a bit to allow some give, loosen that rear "cam" cap's bolts (I had to tap the cam cap a couple times to get it loosened off the plastic cap), loosen the arm that supposedly keeps the plastic cap from coming out, and removed/replaced the plastic cap. Took about 10 minutes total after selecting the right combination of tools that allowed access to the slightly cramped area.

Maybe I should just bite the bullet and do a 1.8 swap so I can have OBDII

A 1.8 swap would still use your 1.6 chassis harness, so you'd still be OBDI. You'd have to do a complete harness/ECU swap in order to have everything else (which is a big project). And if you didn't bring over all of the extra hardware (and weight) that OBDII cars have, you'd have a CEL because the ECU would report missing components. However, if you're looking for something to give you real time data, look into an aftermarket ECU. With most you can output to a cell phone, tablet, or a laptop. And even better is that you'd be able to get some extra power from removing the AFM and having a better tune vs. the factory ECU.

[ya boy willz]

I have the same leak on my 97. How much was the new gasket/seal?

[—RotorNutFD3S—]

On a '97, you'd need a CAS seal, not the cap we're talking about here. I would suggest this part from MiataRoadster vs. the OEM seal: http://www.miataroadster.com/miataro.../i-411190.aspx