Likely Oil Leak Source?

[FL-Frank]

Upon returning from a two hour drive last weekend, I parked the car in its usual spot in the garage, shut the engine off, and opened the rear deck lid to facilitate cooling down. When I opened the lid, there was a very strong oil odor present along with some smoke in the engine compartment. I assumed oil must be leaking from somewhere and onto the heat exchangers.

Looking under the car, I saw oil slowly dripping to the floor. The dripping stopped within 30 minutes of shutting the engine off, and the spot on the floor measured about 5" long by 2" wide. The location of the spot on the floor was under the center of the engine, toward the transmission.

I've since done some investigating, and it appears that the dripping only occurs after the engine has been started, warmed up, and then turned off.

Referencing this diagram, what is the likely source of the leak?

[friggens]

I'd inspect the breather tube as it leaves the case fitting on the top of the engine under the aircleaner. Mine was a later model hose that looked nice, but it had cracks. The cracks simply grew when I cut the hose down, so it was shot. I leaked then, now I don't thanks to nice original replacement from Sierra Madre. The breather housing could also leak, but check the hose: easiest first!!

Cheers & good luck!

[304065]

Frank,

Here are the likely sources of a leak.

#1 source of oil on heat exchangers is valve cover leaks. The good news is that when oil leaks from there and hits the heat exchangers it will vaporize into brown crud, helping you pinpoint the leak. Get under there with a flashlight and see if you can find it on the outboard side.

Triangle Of Death-- formed by the Thermostat o-ring, the breather gasket, and the oil pressure switch gasket. Of these usual suspects I would start with the oil pressure switch gasket-- in your car, the MFI pump oil feed banjo fitting is sandwiched between the engine case and the female adapter for the oil pressure switch. This is high pressure oil so when the pipe degrades it can leak. Next likely is the breather as said by Mike above. And then the thermostat gasket, less likely and there's a pretty close tolerance between the thermostat and the case and the seal doesn't really have anywhere to go.

Next, look at the notch in the bottom of the transmission case or the big hole in the side where the clutch fork protrudes. If oil is coming from the flywheel seal it will be all over down there and can fly onto the heat exchangers.

Next look at the oil cooler seals, they could be leaking.

Those are the obvious areas, see if any of them give it up before thinking it's the MFI belt drive seal or something worse.

[FL-Frank]

Went under to look around...right side valve cover appears to be leaking, and it's also really wet all around the notch in the bottom of the trans. And, when I pulled the air cleaner housing it's also wet around the base of what I think is the oil pressure switch...a gold colored cylinder shaped part with a green and red wire connected to it...

[dummkopf]

Went under to look around...right side valve cover appears to be leaking, and it's also really wet all around the notch in the bottom of the trans. And, when I pulled the air cleaner housing it's also wet around the base of what I think is the oil pressure switch...a gold colored cylinder shaped part with a green and red wire connected to it...

That is one spot where mine was leaking when I acquired it. I sprayed some brake cleaner around it to clean it, then verified the leak by running the engine and using a good light to see with.

[304065]

Yes that is the oil pressure sender all right. That could be leaking and when it does it drips down to the bottom and can manifest as bottom side leaks.

You can use talcum powder to find leaks- just a light puff to dust the surface and then the new leaks show up.

[beh911]

All the culprits are easily fixable on top of the engine. While you are there, just knock them all out.

One more to add to the list forming above:
On the case breather plate (centerline of engine, to the left of your pic), check the hard line oil return from MFI pump into this cover. Wiggle it. If it is loose, JBWeld it back into the cover.

[friggens]

Looks like Rudy is about to get sealed up good. Nice review of potential culprits !

[FL-Frank]

Thanks for all of the advice guys.

I'm scheduled to bring the car to the shop the first week of May for its once every two years full maintenance, so I'll have them replace all of the aforementioned items, and pull the engine and replace the flywheel seal too..."as long as they're in there".

[bjm12001]

Speaking of leaks..............I have several leaks under my 70S with the main culprit being the flywheel seal. Until I have time to drop the engine & replace it, I've been doing some research regarding reseal chemicals you add to the oil which reconditions old seals and minimizes if not eliminate the entire leak. I'm wondering if there is any "disadvantage" with using this additive until I get around to dropping the engine. The one that seems to have the best results is a product made by ATP called AT-205 reseal (see Scotty Kilmer YouTube link). So I ask you guys, what do you think as far as doing more harm then good?

http://www.youtube.com/watch?v=HTT0sejhoOQ