Engine Oil Leak

[simonriley11]

I have recently completely rebuilt my Mk1 engine (about 50 miles so far) and have it running very nicely in my S3 DHC. I have just found an oil leak at the rear of the engine on the exhaust side which is slowly dripping onto the exhaust 'Y' pipe, there is a light film of oil down the forward (visible) face of the engine to gearbox 'tin' sandwich plate which results in drops being formed at the bottom of the plate which then drop onto the exhaust. There are no apparent leaks on the other (gearbox) side of the sandwich plate. There also appears to be a slight weep at bottom dead centre of the sump cork seal retaining channel.
During the rebuild I fitted new Mk1 gaskets to the sump, the upper cork seal holder at the rear of the block, and also new cork seals. I was advised by QED to soak the cork seals in oil for a day or so to soften them (which I did) and once fitted I trimmed them to length flush with the face of the upper seal holder and the rear sump as they were over-length. I used the correct Mk1 sump gaskets, made sure the 'tags' at the end of the gaskets were sandwiched between the cork seals and used plenty of Silicone RTV. I have also since retightened the sump bolts but to no avail.
It looks like I'm going to have to take the engine out again, does anyone have any tips of what to look for upon disassembly and what to do on reassembly to make sure that I don't repeat the problem.
Thanks in advance for any help you can give.

[rgh0]

I am confused by your use of the term "cork seal" at the rear for a Mk1 engine. If yours is a 4 bolt crank with a rope seal for the crank at the rear then there is no cork seal at the rear. If you have the rope seals you dont want the tangs on the sump gaskets to fit between the two halves of the rope seal.

The leak could also be from the gallery plug at the rear left of the block . This plug is NPT not BSP. If the plug fitted did not screw in almost flush you may have a BSP plug which may not seal correctly.

cheers
Rohan

[simonriley11]

Hi Rohan, thanks for your prompt and helpful reply.

Apologies for the terminology, yes they are rope seals that I have fitted. I did trim them back to accommodate the tangs on the gasket so that might be the problem. As the rope seals are both quite over length when you fit them how would you advise trimming them to get the best seal and do I trim the sump gasket so they just touch the rope seal or?

Regarding the gallery plugs I bought these from QED so I would expect them to be correct and I fitted them with Wellseal, however they did stick out more than the ones that they replaced so I will have to check closely when I take the engine out. I don't want to have to replace the other two as well as that probably means taking the engine apart!

[simonriley11]

Hi Rohan, I have an update. I have spoken to Simon at QED this morning and they have confirmed that I have fitted the rope seal/sump gasket incorrectly exactly as you suggested in that the rope seal ends should come together on assembly and the sump gasket should be trimmed to suit. However they also confirmed that the gallery plugs they supplied are BSP and not NPT, apparently they have been using these for years without any issues. When I get the engine out I will be able to confirm this.
Do you have any suggestions as to the best way to fit the seals and gaskets.
Thanks again for your help.

[rgh0]

There was a recent discussion on fitting the rope seals and I think the conclusion was leave them around 1/8 inch proud on both the sump and block this then allows for the sump gasket thickness and ensures compression between the two ends.

There is also a discussion going on now around the plug in the rear of the oil gallery and there have been a couple of similar previously. All this has confirmed it is definitely a 1/4 npt plug. ( the original ford drawings were dug up by a member who made the taps for Ford!). A 1/4 bsp plug is similar and will screw in the hole but it is not correct and may leak. Typically it sticks out of the hole more. I use Loctite 572 pipe thread sealant on the plug

When fitting the cork gaskets use a high tack gasket sealer like Loctite aviation gasket sealer No 3. I coat one side of the cork gasket allow it to go tacky for around 20 minutes then fit it to the block. I then coat the other side allow it to go tacky over 20 minutes and then fit the sump. I only nip down the sump bolts and wait 24 hours before I torque it up. I use a very very small amount of high temperature silicone sealant in the corners where the flat cork gasket meets the road front cork gasket and real cork gasket or rope seal in your case.

I use hex socket headed bolts as its easier to check them when the engine is fitted as you can reach them better with a long ball headed hex key. I check tighten them afetr the first couple of heat cyucles and then again at about 500 miles after that they normal dont move. When tightening them watch the gasket is not being sueeze out. I go more on watching gasket compression rather than the specified torque.

cheers
Rohan

[RichardHawkins]

Simon,

There seems to be frequent confusion between BSP & NPT. The differences are small, and often the threads are tapered. This creates confusion as the wrong item will screw in, but as Rohan says that does not mean it will seal. Nearly all the thread systems on our cars are American, as Ford is an American company. Until the British motor industry went metric, most British manufacturers in the post war years adopted the American thread systems. However, being Lotus, not everything is to one thread system, and you need to keep checking.

Richard Hawkins

[englishmaninwales]

Just to add my tuppence worth, the rope seal is a right royal pain to fit. Just been through this.
Soak both halves of seal in oil at least overnight, trim 1/8" proud of carrier and sump groove, trim sump gasket to fit around the seal, ensure sump flange is flat along its length especially around each fixing hole, glue the sump gasket to the engine block with gasket adhesive, cork gasket to front cover, attach sump and tighten up!
The biggest difficulty is to get the top half of the rope seal, in its carrier with the seal against the crank, to compress sufficiently to allow the carrier fixing holes to line up.
This is why I'm going to convert to a 6 bolt crank / sump/ lipseal / flywheel at the earliest opportunity, as no doubt the rope seal, after all this hassle, will still leak!!

[billwill]

Just to add my tuppence worth, the rope seal is a right royal pain to fit. Just been through this.
Soak both halves of seal in oil at least overnight, trim 1/8" proud of carrier and sump groove, trim sump gasket to fit around the seal, ensure sump flange is flat along its length especially around each fixing hole, glue the sump gasket to the engine block with gasket adhesive, cork gasket to front cover, attach sump and tighten up!
The biggest difficulty is to get the top half of the rope seal, in its carrier with the seal against the crank, to compress sufficiently to allow the carrier fixing holes to line up.
This is why I'm going to convert to a 6 bolt crank / sump/ lipseal / flywheel at the earliest opportunity, as no doubt the rope seal, after all this hassle, will still leak!!

As I may need to do this too (next winter?) can I ask: is it possible to change the rope seal without taking the crank out?

[englishmaninwales]

Bill, yes, I fitted mine after the crank was fitted - I am building the engine up from scratch - but doing it again I would fix the carrier to the block with its half seal before I fitted the crank. Unfortunately all the build guides refer to the later lip seal, except for a picture reference on p 134 in Miles Wilkins book and 2 one line comments on p 128. These references indicate it is fitted after the crank is fitted.

On a fully built engine, I wouldn't disassemble the engine to do this.

[TroonSprint]

Regarding the NPT threaded plug, see my long thread "Can someone identify where my oil leak is?". I have bought the correct 1/4" - 18 NPT plug and it still won't screw in properly - see pics on page 4. I have now ordered a bottoming tap to clean out the threads as per Rohan's instructions.

Mike

[simonriley11]

Firstly thank you all for your help with this.

I'm pleased to say that the engine is back in and the leak has gone. The BSP rear oil gallery plug was not leaking as Simon at QED suggested. I followed Rohan's suggested method and all went well but I also decided to 'pre fit' the two rope seals prior to final build as my crankshaft was already in position and I could see it might be tricky to fit the upper seal carrier to block gasket as the uncompressed rope seal forces the carrier away from the crankshaft on build.

I fitted the pre-soaked over-length seals to the upper seal carrier and the rear of the sump and then rolled the side of a large socket around the inside of the seals to push them into the channel section in the two items. I then attached the upper carrier to the block on one of the lower (shoulder) bolts (just nipped up) and then with a small G clamp carefully pulled the other side of the carrier so it was flush with the underside of the block so the seal was formed to the crankshaft. I then removed the upper carrier and attached the sump using packer washers between the sump and the block to squeeze the sump rope seal to the crankshaft. I then trimmed both the rope seals to plus 3mm on the ends and then built it all up with the sump gaskets and sealants.