OIL LEAK : Head Gasket or Rear Main?????????
 

1992 1.6 greddy, intercooled running 6psi. Has about 111k on engine, 40k on turbo setup. Have developed an oil leak. Dripping off bottom of oil pan, not just a drop ghere and there but 3-4 drops evertime I park it. Getting the wife REALLY upset. Already replace the cam sensor o-ring. Its dry there. Valve cover gasket is dry all around it. The oil line to the turbo is not leaking, I was hoping for that one. Gotta be either the rear main or head gasket. Last week, jacked up the car and totally degreased the engine area in the rear. All was dry. Two days later dripping off oil pan again. The clutch slave cylinder is not losing any fluid either. There is now some wetness between the head and block on the exhaust side under the exhaust manifold. It was bone dry 3 days ago. Could the head gasket be leaking and draining into the bellhousing and draining down the back of the motor that bad? Only other place I can think of is the rear main seal. There is oil inside the bellhousing, I pulled back the clutch slave cyl. boot and reached in there. It is also dripping out of the bellhousing weep hole. I got to fix this, If anyone has any thoughts on which one I should do first, or which one might be more prone to leaking, thanks for the help. :crx:

If it is coming out the weep hole I would say it is most likely the rear main seal. I highly doubt it is the head gasket.

I'm hoping for the rear mainmyself. The engine runs too good, no coolant leaks at all. But can the oil slinging around in the bellhousing get up to the head to block area on the drivers side?? Thats what is messing with me. Are there any tricks in doing the rear main, other than same stuff as any other I've done.

Flashlight/penlight and a "mirror on a stick" will tell you if it's coming from the rear of the cylinder head...but knowing how fate works, I'd bet on rear main if it's dripping from the bell housing weep hole:-(

Add a bottle of uv dye to your oil and get your black light ready.

I like the idea of the uv dye, I've got an open weekend in two weeks, so I'm trying to determine what I'm doing by then. When I said coming out of the weep hole, that is true, but the bottom of the whole pan, and around the side of the block on the drivers side is also quite wet. Dang it just seems to be wet all around the back. Thanks for the uv idea. That will be tomorrows step.

Be sure to refill the oil that is leaking from where it may be. Sounds dumb but Ive seen and heard about people who knew about the leak and still forgot that its missing inside if its outside.

just throwing this out here but i have the same problem and it was actually coming at the bottom on the dip stick the oring was worn out.

Oddly enough, my '92 developed an oil leak that did eventually turn out to be the head gasket.

I originally thought it was a CAS ring or VC gasket, as oil was winding up at the TOP of the valve cover as well as down below. I replaced a bunch of stuff before finally pulling the head. Found evidence that oil was leaking from the rubber o-ring cast into the back of the gasket. After gasket replacement, all was dry. Which makes no sense, as oil in that region of the head isn't even pressurized.

Moral of story: oil can wind up in weird places. Did you remove the AC compressor? If so, did you remember to stick a new, shorter bolt into the one hole that has to have a bolt in it even if you remove the compressor? (Hint: it secures the far edge of the oil pump to the block.)

What's the torque spec for the replacement bolt, Joe?

14-19 ft/lbs.

It's this bolt:

https://www.miataturbo.net/attachmen...ine=1329520384

Oddly, I can find no mention of installing it in an engine without A/C, but if you omit it, then regardless of whether you have A/C or not, oil will very slowly weep out from between the oil pump and the block.

When removing the A/C, the bolt must be shorter than the original bolt by the thickness of the part of the compressor bracket that it normally goes through.

Thanks Joe!

I believe the bolt is 35mm or 40mm. If you search m.net you can find the exact size.

8x1.25x45mm, already have one in in fact. I was just making certain I didn't undertighten said bolt.

or you can use a x50mm with a washer.

thanks for the input, I will be trying the rear main this weekend, there is still wetness around the drivers side head edge, but lots of drips under the pan, might as well put a new clutch in while i am in there. Any big no-no's or tips for the rear main job. What is the best way to get the shifter boot out. Also, how to hold the flywheel with out buying the specific tool. Can I use an impact on the flywheel bolts or is that a big no-no. Thanks again.
jim