Where's the oil leak?

Our completely rebuilt 4.2 engine in our '67 OTS with approximately 100 miles is dripping oil, only when running (1 every 5 seconds or so), down the middle backside/rear of the oil pan. It is not coming out of the bottom hole in the bell housing. Where is the failure likely to be and how do I rectify it?

First check the banjo bolts for the oil line at the back of the head. Then check the rear main seal through the bell housing from underneath. They are the usual suspects you need to round up.

Since that’s the lowest part of the engine it’s coming from up above and running down. To rule where it’s not leaking from try taking a dry tissue and wiping the engine starting at the top and see if you find any evidence of oil. With only 100 miles on it the oil will be clean and hard to see and maybe it’s something simple like the oil pan gasket but I’m thinking the rear seal and you know what that means:disappointed_relieved:

One of those blue paper towels like gas stations sometimes offer to clean windscreens or a cheap brown paper towel from a public restroom sometimes show traces of oil better than the usual white paper towel or tissue.

Start high (cam cover gaskets) and work down.

Talcum powder, too: sprinkle it around the back side of the engine, and oil leaks almost luminesce…

1 Like

Thanks, guys!
I should have included more detail… From top to bottom, side to side, front to rear, the engine is dry. The only trace of oil is the drips that run down the center rear of the oil pan AHEAD of the reaction plate. There is no trace of oil coming from behind the plate or the bell housing.

Likely the rear pan seal, and/or the rope seal.

My thinking is that since it is dripping when the motor is running (and the oil pump) it’s not the pan gasket or the rear pan seal. If it was just a seal then it would be constantly dripping. I’m not sure how low you can drain the oil and still run the engine, but if you can drain it lower than the rear pan seal and it still leaks that only leaves one other choice the rear main seal. It the engine was rebuilt by a garage then it’s their problem. If not you could try some Bars rear main seal repair you would need two cans for the e type oil capacity.

My thinking is that since it is dripping when the motor is running (and the oil pump) it’s not the pan gasket or the rear pan seal. If it was just a seal then it would be constantly dripping. I’m not sure how low you can drain the oil and still run the engine, but if you can drain it lower than the rear pan seal and it still leaks that only leaves one other choice the rear main seal. It the engine was rebuilt by a garage then it’s their problem. If not you could try some Bars rear main seal repair you would need two cans for the e type oil capacity.

Art, the oil level is not anywhere near the rear mail seal as it’s below, or supposed to be, the the sump baffle.

Bob
889076
Plymouth, Mi.

first I would double check to make sure I hadn’t overfilled the crankcase while praying that was it.

if that wasn’t overfilled, I would try running a qt low to see if that made a difference.

Then I would run the car a little more while asking the Lord to swell up the seal.

best of luck to you and me If I ever get mine started.

It most certainly can be the rear seal: when the engine is running, that seal sees LOTS of oil: Ive actually fixed that issue on a few Jags. Someone on the list a few years sgo—Pekka?— had that exact issue.

Problem is…determining it. I diagnosed it by elevating the car, taking off the tin splash shield, then watching while the car is high idle.

What I was thinking was that wouldn’t oil leak out of any bad seal below the oil level whether the motor was running or not? So if the oil only leaked when the motor was running that would indicate that it was coming from above the oil pan gasket. And if so then the area I would be concerned with would be the rear main seal which would leak faster when the motor was running. That’s assuming that it isn’t running down the back of the engine from say the valve cover gaskets.

Sounds like a rope seal. Make sure the crank venting system is free and clear. Any blow by will cause a pressure buildup in the crank if it cannot breathe. Not as much of a problem with the Series 1 cars but the Series 2 cars had much smaller venting pipes and can restrict ventilation. Other cause would be the rope seal not having been properly sized using the factory tool. UV dye is the easiest way to tell where it is coming from. This is available at most Auto parts stores. Just get the dye made for engine oil and a black light.Run it for a few minutes and you will see bright green wherever it is coming out. You don’t even need to clean off the previously leaked oil.

1 Like

My money’s on the rope seal too. It was the one thing I did not attempt to do myself when I did the rebuild, enlisting the help of a local Jaguar XK engine specialist who has the proper Churchill sizing tool and the experience to use it. He told me even when installed and sized by the book there’s still a possibility of a leak, though minor. A drip every five seconds may not qualify as minor. Don’t know. Many factory installed rope seals started leaking not long afterward - euphemistically referred to as the “factory rustproofing system”. My E was a successful example as the rear seal leaked constantly and the steel inboard of the long floor rails was essentially rust free.

There’s been a fair bit of discussion on the rear seal. Some have given up after repeated failed installation attempts and having their crank machined to take a one piece modern seal, though there are reports of the mod going wrong.

I had a pro built motor (not jag) that had too much blow by. The ring gaps were aligned on one piston instead of being staggered. The pro said “of course I staggered them, they can move by themselves sometimes”.

Still trying to determine the source of my rebuilt 4.2 oil leak… since it emanates down the center rear of the oil pan and none is evident from the bell housing (Cangialosi 5 speed), I’m assuming (yeah, I know) it’s either the rear pan gasket or rear main seal.

When the machine shop who has been well known for decades for their XK expertise did the rebuild, items on the invoice read, Parts: “1 kit - rear main bearing seal - $337.50” and Labor: “Grind shaft for new seal - $300”. If I’m not mistaken, I was told (it’s been 3+ years) that this was a wise investment due to historic issues with the rear main seal. Does that provide any guidance for solving my leak? Should that $637.50 investment steer me away from the rear main seal and towards the pan gasket as the source or …?

Well, that answers the question about the rear rope seal. You don’t have one. Yours has been converted to the 'new & improved" seal. Now that the crank has been ground to fit, you are stuck with it unless you want to fit another crank. If it is the rear seal, you hopefully can find the brand or source and get another one. Rarely is it the pan gasket but the dye should show it if so. From your description, it is the rear seal. Engine still needs to come out and partially apart to replace. I do not recommend the conversion as when properly installed and sized, the rope seal gives very little problem and since it is not rubber, it does not dry out, crack and leak with age.

1 Like

If it’s the crank seal, FYI there are two lip seal kits that are generally available. One uses a spring to hold the seal against the crank and one uses a stiff Viton seal (no spring). The kit with the Viton seal (Terry’s) requires that the crank be ground to a very slightly smaller diameter. So, if you have the spring seal kit you would have the option of grinding the crank again and switching seal kit designs…or just replacing the faulty spring seal. If your engine builder does have to remove the engine for a leaking crank seal, I’d insist on being there to see for myself why it leaked. There seems to be room for installation error with the spring kit. Also check the diameter of the machined surface yourself. By the way, $300 to grind that one surface seems pricey. I’m using the Terry’s seal kit and it does not leak at all, although time on the engine is minimal with just a few shakedown blasts around the neighborhood.

I agree: I never really saw all that much of an issue with the rope seal, properly-installed.

Shame I never had the proper Churchill tool to do it…:stuck_out_tongue_winking_eye:

Every time I see the ‘title’ of this topic I think of our Oil Leaks (Jerry alway felt that adding ‘tour’ was redundant) so I keep waiting for Geo, aka J. Lucas, to announce the Grand Circle Oil Leak.
Cheers,
LLynn
PS: sorry for the thread drift :wink: