I am not a TR expert. But I DO KNOW oil leaks. And despite all the humour about them.. don't like them. Of course, the medium is designed to keep them hidden and they adhere to odd surfaces more than water. Changing oil for fresh makes them even harder to see and they express themselves best when the oil is under high pressure. A Sherlock Holmes nightmare. On the other hand, they are rarely serious...tho always annoying.

Familiarity with the engine (leaks are often found in the same places as others have) and/or some technology can help. I haven't had a Morgan with a leak since I figured my V8 engines out in this area. I will only tolerate a bit on the starter and right side of the sump the day after a change the oil filter.

There is tons of stuff on TRs and oil leaks on GoMoG. But start with a diagnostic additive that shows up in the dark with a UV light. I would refer you to a gomog article but I am lying on a beach at the moment (lucky me!) and I can't search the site much. but

That will tell you where it is coming from if you are religious about setting the correct conditions. It will likely be a seal or gasket area..the valve cover, the sump or the rear seal...sometimes all three..so always start with the top one.

Or you can use the scatter gun method. Address every thing the could be the case and hope. Here is a start.

http://www.gomog.com/allmorgan/plus4oilleaks.html
http://www.gomog.com/allmorgan/plus4index.htm Try this one first!!

GoMoG LAW of LIFE:
The correct approach to a Morgan mirrors the correct approach to life.
Enjoy it, don't fret about it and be confident that, whatever happens,
you can fix it.

Sometimes leaked oil droplets end up on the chassis crossmember while driving, but ooze downward once parked, falling to the ground below. Take a 1/2 ounce of motor oil and pour it on the floor. Do the same with, say, 1/4 ounce for comparison. Give it a few days to spread out and see how wide a patch it leaves. That will give you an idea of how much oil your car is actually losing.

Duncan

If you get your engine and gearbox nice and clean you can also just spray on some "developer" from a metal crack detection kit. It's probably not much more than fine talcum powder suspended in a liquid carrier that evaporates quickly after spraying it on. It leaves a white powdery film that will show leaks in normal light.

Duncan

That is exactly what happens but I will do the test

I am not enamored with oil leaks myself, but...

This is not really much of a mystery.

First, clean the engine. Once you get rid of the oily grime, it is easier to spot the leaks.
I often (mostly) use a pressure washer, but you can also use stoddard solvent or paint thinner (use a respirator mask) with an air sprayer.

All of my cars have properly installed and sealed ignition systems, so there are no problems with starting if I use a pressure washer.

Brake parts spray/degreaser is also good to use, but in a well ventilated area.

I know... I am going to get flack about "washing the engine", but I have been doing this for, um... HALF A CENTYRY, without problems (this includes several Healeys, Suneam Alpine and Tiger, Alfas, a Ferrari, one Bugatti Type 57, Rolls Royce PIII, as well as all my "modern cars". But then, I do have a proper ignition system, and my electrics are always in top shape. AND. as an added advantage, hoses and wiring last a lot longer when not bathed in oil blow-by and heated by the engine.

Of course, this is somewhat complicated by the wood in the Morgan's superstructure, but if one takes good care of the car, it can be wiped down every couple of months using a cleaner such as Pledge on the smooth undercarriage parts. Cleanliness requires you to check the car regularly, and reduces emergency maintenance chores.

You can also use brake parts cleaner spray, Simple Green aircraft degreaser (it has a corrosion preventative), on the oily bits like the transmission and the engine... Or just a lot of rags to wipe everything down.

Put down a nice large piece of fresh cardboard, or a clean drip pan under the car so that you can see the location of the leaks more clearly.

Then, drive the car and check for leaks. You should be able to see the source of the leaks after you park the car and put it on stands.

You can also use a dye, and a blacklight, which is indeed a very effective tool to find leaks. This works best on a clean engine, BTW.

Triumphs don't have a flexible rear seal, using a spiral slinger to retain the oil while the engine is running. This will usually give a drip or two, and mist everything aft of the engine. This is something that we all have to live with (my BMC A engines have this same setup).
There is a seal kit that looks reasonable, but... You need to disassemble the entire engine to free the crankshaft for machine work to fit the seal. If you have a good engine, you probably don't want to do this. I know that I would not.

Rocker cover gaskets often leak, especially if you have the cork type, or someone has tried to replace you seal with RTV. Find a "permanent" type of seal. These will seal far better. Also make sure that the sealing surfaces are true on the rocker cover, and don't overtighten. While I am a +8 owner, my leaky rocker cover gaskets were replaced with permanent neoprene gaskets (installed dry), and the leaking stopped. No additional sealers were necessary.

Front cover seals (crankshaft and perimeter) often leak, and you can see where the oil is dripping down from the crank shaft. It will usually be revealed by the clean bit, with dirty oil around the drip. These are relatively easy to replace.

Pan gaskets are also problematic and can leak at the main bearing caps, especially if there are rope or felt seals. Seal replacement is the thing to do here, making sure that everything is clean prior to installing the seal. I will occasionally use a sealer with the gasket, such as Hondabond or Yamabond (same thing, different dealer). Occasionally, there may be a rubber type seal option replacing the rope or felt. In any case, the use of RTV is often recommended at the edges where the felt and the pan or pan gasket may interface.

Hondabond and Yamabond may be used to tack or assist the paper gaskets on oil pans and front covers. Be neat.

Head gaskets can also be the source of a leak, generally caused by an improperly installed head gasket, or missing O ring. I had this once. Fortunately, head gasket replacement didn't take that long. The problem was a head gasket O ring that didn't seat properly. Likely my fault, or that of the head gasket. My suggestion is that if you have a problem with a head gasket oil leak, is to use a Payen head gasket set to do your replacement, and make sure that both the block deck and the cylinder head is perfectly clean. You may even want to resurface the cylinder head to ensure a good seal.

When I used to judge Rolls Royce at the Concourse, we had guidance as to what constituted a "leak", and what indicated "lubrication".
"A film or mist of oil about a joint is considered lubrication". "A puddle under the engine indicates a leak". Small drips are just small drips, and indicate lubrication, I guess... Until they become a puddle.

These engines without rear main seals can leave the occasional drip, but there should be no leakage from the usual gaskets, as noted in the previous post.

Now, have at it. You will not be able to eliminate all the leaks, as some are built into the power unit.

I remember when I described my old Matchless G80 as " A device used to apply a protective coating of engine oil to the garage floor".

Your Triumph TR3~4 engine is not that bad... Have fun!