Oil Leak diagnosis *pics*
 

Does this look like the dreaded dowel pin leak?

It leaking from the area circled in red, and then leak down the side of the block where I circled blue.


First pic is a overall shot of the engine to show where the close-up pics were taken from

it could be. but remember, when you add oil and are not careful, the oil can spill and it can collect there and fool you into thinking its something major. i would clean it up really well and keep checking on it for a few days.

I pressure washed it all first, and then started the engine. After a minute or two I could see it seeping out between the 2 different kinds of metal where I circled the pics.

sounds like you have teh "leak" all the leak is are bad washer type gaskets that harden. requires engine removal and dissassembly.

Have you done it before? How big of a job is it? Is it possible with the engine still in the car (remove the rad & fan to get access etc) and using regular hand tools?

Oh, and are these the same 'gasket' as the o-rings that seal the oil cooler to the block? I ordered 4 of everything when I replaced those, but only ended up using 2.

the engine has to be dismantled. they are not the same type of o-ring. they are a paper type. you can drive for awhile with the leak, just monitor your oil level.

To clear a few things up:

1. That is the usual place for a dowel pin leak.
2. It is caused by a degraded rubber o-ring.
3. The engine needs to be disassembled to replace the o-ring.

If the engine is in good shape, all you need is a seal/gasket kit. If you plan on doing any internal upgrades, this would be a good time to do it.

A dowel pin leak won't really harm the motor, but it can get get quite messy. Especially underneath the car. I had oil spray all the way to the rear axle on mine, in less than 1500 miles of driving.

The funny part about that was, it softened the undercoating, to the point that I could wipe it off with a scrub pad and paint thinner. The other side I had to chisel off before I could sand blast the body.

Felix Miata's site (http://members.ij.net/mrmazda/cfaqtext.html#EXTLEAKA) states that, ". . . These are also used at the sandwich joints, but their job is to isolate and seal part of the path between oil pump and filter. This path includes dowels than align the engine sandwich, so they are referred to as tubular dowel o-rings. When they cease to function correctly, oil pressure forces the oil through the joint externally, where you can see the leaking near either end of the Mazda logo on the rotor housings, and sometimes internally, into the cooling system. Adding transmission sealer to the oil can sometimes stem the flow, but the correct fix is engine overhaul. Failure of these is by far most common on 12A engines using the oil cooler placed between the oil filter and engine block, as this design results in higher oil temperatures than models with air-to-air oil coolers."

As mentioned, clean everything off with brake clean and compressed air and recheck for new leaks. First, if it is a rear main seal you will see it inside the bell housing with the inspection plug removed. Engine off! You don't want the flywheel to take your finger off... I would question the operation of the PCV if your getting multiple oil leaks. Pressure is building up with nowhere to go and blowing out seals. Now would be a very convenient time to have access to a smoke testing machine :D

it is rare, but could also be a passenger side dowel pin or tension bolt seal leaking.

I would not run a drill bit and screw into the rear main seal. They should pry right out with a seal puller or at the very least a small pry bar or flat head screw driver. Reinstall with a seal installer or a block of wood or hockey puck.