Lotus Elan

Replace rear sump seal with engine in situ?

PostPost by: Charles73 » Sun May 01, 2022 1:24 pm

Rather frustratingly, my newly rebult TC has a leak *almost* certainly coming from the rear of the sump. I suspect its the junction where the sump gaskets meet the rear cork seal that is failing. The flywheel is dry and bellhousing only has oil on bottom edge, suggesting the leak is below the rear crank seal (I think?).

I was just pondering whether or not it's possibly to replace the cork seal by removing the starter motor and dropping the sump enough without having to lift the engine...

If not, I don't think I'm concerned enough about the drip to take the thing apart again just yet!


Many thanks
Charles
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PostPost by: Hawksfield » Sun May 01, 2022 4:57 pm

Hi
It can be done but its not without risk as you cannot be sure its not the lipseal.

An elan is also much more difficult because of the unremovalable cross member

You dont say which type of car you have its best to display this in your ID
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PostPost by: Charles73 » Sun May 01, 2022 6:10 pm

It's an S4 with fixed chassis crossmember.
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PostPost by: StressCraxx » Sun May 01, 2022 9:06 pm

If you want to find the true source of oil leak, try pressurizing the crankcase with 1 PSIG of compressed air. Seal the crankcase by plugging the dipstick tube and connect a regulated air supply to the vent in the head.

With pressure applied, spray soapy water around the area you suspect to be leaking. The air flowing from the leak will make copious amounts of bubbles. If you don't get bubbles, keep spraying away from where you think it's leaking. You may be surprised.
There is no cure for Lotus, only treatment.
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PostPost by: Lotusian » Sun May 01, 2022 9:43 pm

Before you do anything drastic, check the back of the cylinder head around the cam cover seal, half-moon plugs and oil filler cap. A leak here can run down the back of the block and appear at the bottom of the bellhousing.
Don’t ask how I know.
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PostPost by: Elanintheforest » Tue May 03, 2022 4:54 pm

I have another place to look. I rebuilt a Twincam for my Lotus Cortina a couple of years ago, and noticed a bit of oil at the back of the sump and a little puddle on the floor.

I was convinced it was the rear seal, but checking around the top of the petrol pump was also oily, and the leak was coming from the rubber tube that allows oil to drain from the head to the sump. I simply hadn't fitted the tube properly at the head end.

When it leaks from the top (cylinder head) seal, the oil follows a path to the back of the engine via the webbing on the block, pushed along by the wind from the fan. It finds the end of the block and dribbles down the bellhousing, dripping out of the bottom of the housing, simulating a rear crank seal failure very well !

I refreshed my old Elan engine a few weeks ago as that had also developed a couple of oil leaks (after 33 years!) and the main culprit also turned out to be the rubber tube seal to the head.

The rubber tube can be easily replaced without stripping the engine, but you will have to get the carbs off. And there are two types of tube; a very hard / stiff one, which you cannot fit without stripping the engine, and a soft one that bends through 90 degrees allowing accurate fitting.

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PostPost by: rgh0 » Wed May 04, 2022 12:27 pm

There is a breather hole in the bottom of the mechanical fuel pumps that can also leak oil out and it track down to the back of the engine - no shortage of places to check.

I have replaced the sump gasket in situ in my Elan due to the gasket at the rear where it joins the square semi-circular section not mating up properly and leaking like you suspect - I take extreme care these days to make sure it does not happen when building engines :lol:

It is why my I first made up a removable cross brace for the chassis in my car so I could do that job as while theoretical possible to do just by dropping the sump a little to fit new gaskets, you need to remove the sump completely to have any confidence your doing it right and and have the gaskets properly in place. Its hard enough doing it on an engine stand with the engine upside down let alone lying under a car on jack stands :shock:

To remove the sump fully you really need to remove the cross brace or remove the engine. Maybe if you jack the engine up to the maximum possible you get enough room to fully remove the sump with the cross brace in place but I have never tried that.

cheers
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PostPost by: Mazzini » Wed May 04, 2022 8:42 pm

Maybe in the future somebody with an early engine will come across this thread.

It's probably worth noting that on a Mk 1 engine (four bolt crank / rope seal), the dirt shield (between the engine and gearbox) is in one piece. Even with a detachable cross brace it's really difficult to drop the sump as the back of the sump fouls the dirt shield, as the sump comes down the dirt shield pushes it forward so the front of the sump hits the cross member. The only way to do it is to separate the engine and box enough to remove the plate, then the back of the sump can be pushed into the bellhousing space, up to the flywheel, which gives the front of the sump sufficient clearance to drop down...at that point you might as well have taken the engine out.

When Ford introduced the Mk 2 engine they made the dirt shield in two pieces, maybe they had Lotus in mind or perhaps it was just a coincidence that another Ford model shared the same issue.
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PostPost by: Gordon Sauer » Wed May 04, 2022 10:02 pm

To tag into this a minute, my engine was rebuilt in 77 and I drove the car probably putting 1000 miles on it till 78, been off the road since then with 4 to 5 times a year cranking on the starter as it sits in the bare chassis; should I replace like the rear main seal and the rope seal and everything on this 67S3 Elan drophead coupe before it’s all back together? A mostly good idea? thanks Gordon
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PostPost by: Mazzini » Fri May 06, 2022 5:46 am

Personally, I would fit new gaskets and run the engine in the chassis before dropping the body back on.

There is a graphtite rope seal available in the US. It seems to work well in making an oil tight seal, but unless staked to the housing they can rotate.
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PostPost by: Mazzini » Fri May 06, 2022 8:21 am

rgh0 wrote:There is a breather hole in the bottom of the mechanical fuel pumps that can also leak oil out and it track down to the back of the engine - no shortage of places to check.


Hello Rohan,

I never knew that, where is it?
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PostPost by: types26/36 » Fri May 06, 2022 1:52 pm

Mazzini wrote:[quote
I never knew that, where is it?


Leaks oil when the shaft seal is defective, the seal is not usually included in a kit although I seem to remember some Land Rover kits have the shaft seal.
Attachments
pump hole.JPG and
PUMP SEAL.JPG and
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PostPost by: Mazzini » Fri May 06, 2022 2:59 pm

Thank you for that!
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PostPost by: Charles73 » Thu May 26, 2022 7:47 am

It turns out it was the rubber breather pipe that was the source of this leak. Removed and refitted with better sealant (black Sealey gasket sealant) and I have next to no oil escaping. Very happy
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