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Oli Leak mystery

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Basil

Basil

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I've posted here a long time about about a nasty oil leak from the rear seal of my 78 Spitfire. I have twice replace the seal with new and yet the leak persists. The engine had been rebuilt buy an outfit when I was back in Illinois before moving to New Mexico, but I don't think they rebuilt the bottom end (crank). The symptom is that the car doesn't leak much oil when running, but as soon as I shut it off, it pours several tablespoons full of oil out the rear. Anyway, last night I was driving home from work and took a different route than usual. I ended up stopping in to see "Doctor Jag." Dr Jag is Bruce Kirby, a friend of mine who used to be the lead Jag mechanic for the local Jag dealer until a falling out with their management caused him to break away and open his own shop ( Doctor Jag ). I was talking to Bruce (a rated Master of Masters Jaguar mechanic) about the problem and he suggested that he suspects the problem is the rear main going wobbly. he explained the physics of it to me and it made sense. So now I am on a mission to once again pull the motor on the Spitfire and check the crank and the mains. I'll take it to a local machine shop and have the crank checked and turned if needed and have them properly install new bearings. While I'm at it I'll have the pitson rings and walls checked to make sure they are seating properly. I read somewhere that improperly seated rings, which could happen for example if the walls were not properly prepared before install, could cause blow-by and thus cause increased crankcase pressure which could also be contributing to the problem. My money is on the rear main being the real issue, but I migt as well check all possibilities while I have the motor apart. If anyone can think of anything else to check while I'm doing this, I'd love to hear about it.


Basil
 
I'm not really familiar with the crankcase ventilation on a Spitfire, but my first thoughts as I read this was excessive pressure, but only to a point.

If that is indeed the case, you could theoretically drive the exact same route with a taped down, but very loose, oil cap or less any PCV, if one exists. That should relieve all crankcase pressure and then you can see if the leak persists. Fluid will only leak from the weakest point under pressure, so do you see any leaks at the oil pan gasket, timing cover seal or cover gasket?

If it still does, then you may be forced to remove the crank. It is not as rare as one would think to see a perfect seal from the mating surface of the crank journal to the seal itself, but oil leaking by the outside diameter of the seal itself. If the metal shell and the block surface were not mated properly (no fault of the installer, just a mismatch) and no sealer was put on that surface, you may have leaking in that area and not the most likely area around the rubber and crank.

Just some food for thought............
 
WHERE specifically Basil can you pinpoint the leak,in other words where IS the origin of the leak.One thought is that Spitfires are notorious for leaking at the back end of the head at separation point between the head and the block,if its wet their retorque the head and the valve cover.This has been a common complaint over the years.BUT then on the other hand it probably caused by cabin fever.HO!HO!HO!& Oh!MERRY CHRISTMAS BASIL.
 
It does seem to be leaking out if the rear seal, that much I'm 99% sure about. Since I've replace the seal twice, I'm going to tear down the bugger again and check EVERYthing I can think of, to include checking the Crank and Mains thoroughly (and check everything else that has been suggested.) I am bound and determined to get this leak stopped, or at least slowed down to a small drip.
 
Won't be a Triumph if you stop it comletely!
 
What about at the "freeze" plug that seals the back of the camshaft bore? I had an early spit years ago that had a pretty significant leak from there, and it just runs down and looks like a RMS leak I would try the dye first so that you are certain that the leak location is pinpointed before you perform major repairs. I use the UV dye all the time.It is cheap and an easy way to be sure.
 
I don't know what type crankcase breathing system this car has, but if it is a pcv system, then the crankcase is - should be under slight vacuum while it's running. Therefore no leak while running. When the engine is stopped, oil remaining in the rear seal area is not being pulled back into the crankcase and if the seal is bad and the drain channel is not optimal it can drip out.
 
racingenglishcars said:
if the seal is bad and the drain channel is not optimal it can drip out.
Click to expand...

Well, the seal is brand new (twice), so that leaves the draion channel not being optimal, which is sort of what my fried the Jag mechanic was suggesting. That's why I'm going to pull the motor and have a good long look at the crank and the Mains. Also, I'm not sure if a 78 has the freeze plug on the end of the crank, but if so I will have a good look at that as well.
 
Basil:
In my 40 years of experience I have run across a small problem that had very similar symptoms.
The surface for the main seal is slightly smaller than normal. This means, even a new seal doesn't need to wear very much before it begins to leak. The fix is a collar on the crank, to take up the extra room that is there. These are called ready seals (at least here in Canada)
I would do what the Jag gentleman said as well, and check everything just to be safe.
This may not be the problem, but worth inspecting.
Dave
 
14dna said:
Basil:
In my 40 years of experience I have run across a small problem that had very similar symptoms.
The surface for the main seal is slightly smaller than normal. This means, even a new seal doesn't need to wear very much before it begins to leak. The fix is a collar on the crank, to take up the extra room that is there. These are called ready seals (at least here in Canada)
I would do what the Jag gentleman said as well, and check everything just to be safe.
This may not be the problem, but worth inspecting.
Dave
Click to expand...

That was my first thought when the first replacement seal leaked. Inspection of the crank end did not seem to indicate any obvious or exceess wear and the new seal "seemed" to be fitting nice and snug. However, I'll not rule it out when I tear down the motor this time. I place to have a machine shop look at the wear on the end of the crank to see if there is any wear that is measurable where the seal sits.
 
Basil,

Before you pull the engine, run it for a while with the dye in it. It may help when you get it apart.

Or, it may save you taking it apart. Pretty cheap (and accurate) diagnosis.
 
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