Oil Leak from Hell!!

“So, Mr. Bohon, what are you doing this weekend?” 

“Well, I’m pulling my engine out of my miata.” 

“What for???  Did you finally blow it up with that crazy turbo?” 

“Nah… Got an oil leak.” 

“You really are nuts, Mr. Bohon… nuts!”

 ...well that’s pretty much the jest of several conversations I had with my co-workers, family and friends that aren’t in the miata circles.  Of course, once I explained to them the details of my prior efforts to fix this leak, it seemed to become less of a wild idea to pull the engine and do it right.

So why did I pull my engine?  Well, it all started about 2 years earlier when I discovered a very small leak dripping onto the garage floor after an overnight parking.  The leak appeared to be coming from the rear main crankshaft seal, and since I had recently installed a high performance (and high price) clutch in the vicinity of the leak, I was quite concerned about fixing the leak soon before the clutch was ruined.  So… out with the transmission, swap out of a seal and re-assembly.  All was better, right?  Wrong.  The leak was still there.

What else could it be?  Well, the oil pan seal looked to be a suspicious area and others I had talked to mentioned a similar problem of which ended up being the oil pan seal.  So, another weekend, another miata-job.  I lowered the front suspension subframe, pulled off the oil pan, cleaned up and applied fresh sealant and re-assembled it all.  Surely this would fix it, right?  Wrong!  Arrrrggg!  The leak was still there.  At this point I was tired and wanted to give up.

Well, I was near the 60k mileage marker at this point so a timing belt replacement was in order.  While changing the timing belt, my engine got a new valve cover gasket, cam angle sensor O-ring seal, both cam front seals and a front main crankshaft seal.  SURELY, with this shotgun approach of changing all these seals, the leak would be history.  It would have to be!  After all, there’s not too many more oil barriers throughout the engine.  ...You guessed it… WRONG.

At this point, I did finally give up.  I had been using Mobil 1 synthetic motor oil and as a last chance effort, decided to change back to a conventional motor oil.  This seemed to have fixed the problem, for a few weeks, but the leak resurfaced.

One day in July 2000, I noticed that the little leak had turned into a BIG leak and that I could no longer ignore it anymore.  I HAD to fix this leak!  By coincidence, my good miata friend Nigel Soult had just purchased an engine hoist and stand when his motor failed on his ‘91.  Nigel let me borrow his equipment and away I went.  In less than 5 hours, my miata went from a driveable vehicle to an engine-less carcass.  I felt like I was getting into open heart surgery.  I was amazed at how easily the engine came out of the car, but then again, at this point I was starting to get used to having to do big jobs on this car (so it wasn't too intimidating).

Once the engine was out, the leak(s) were much easier to isolate.  The engine stand allows the engine to be flipped over and inspected/worked on from a variety of angles.  An ergonomic dream in auto repair.  Close inspection revealed that oil was indeed leaking from the drivers side rear portion of the head gasket and that more oil was also leaking from an area around the front main seal.  So… I removed the head, had it inspected for warpage (which, it WAS a little bit warped… and was fixed by shaving of 0.005 inch) and to clean up the combustion chambers and vacuum check the valve seats.  Other than the minor warpage, the head turned out fine.  The tops of the pistons were carefully polished with a small Dremel tool while the head was off.  Re-assembly was done with a fresh head gasket.

IMAGE5.jpg (250215 bytes)  Here's a pic showing a cleaned up piston next to a dirty one.

IMAGE10.jpg (312221 bytes)All cleaned up and ready for the head.

Near the front end of the crankshaft, it became apparent that the front main seal and oil pump gaskets looked to be contributing to the oil leak problem as well.  So, off with the oil pump.  I was so glad to have the engine out at this time because changing an oil pump on the miata with the engine in the car is not easy.  After applying new gaskets and seals, the engine was put back together again and re-installed into my miata.  A few turns of the starter motor, a few coughs of the engine, a few puffs of smoke out the tail pipe and away it went, running like a champ.  Now the real test.  Is the oil leak gone?  Well………….  I am HAPPY to report (at the time of this writing) that as of over 6 months of driving, we now have, “No Runs, No Drips, No Errors!  OIL LEAK FIXED… the effective yet HARD way!