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MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - Rear Main Seal

I have installed the Moss Rear Main Seal 3 times with 100% success. It is a daunting process to be sure. Anything with 450+ steps is bound to be difficult following are some helpful tips I have found useful.

You must use the blue Teflon seal. Seals of the same dimensions can be obtained, but they are designed for use in a big truck and earth moving equipment where their function is for holding back gear oil in axel applications where rotation is not in thousands of RPM. They will fail.

Bearing clearances must be to spec or better. Personally, I have the crank ground to fit the bearings after the bearings have been installed and measured to allow 1 to 1 ˝ thou clearance. Also have the crank flywheel and clutch cover balanced and marked as a unit.

Use JB epoxy, not silicone to bond the aluminum seal halves to the back and main bearing caps after verification of their concentricity to the crank. Block half first. Surfaces must be clean, clean. If masking tape won’t stick it is NOT CLEAN – use acetone and rough up mating surfaces with 80g sand paper.

Dry fit everything before bonding and check for clearance. The speedy sleeve. When installed on the crank shaft hub should protrude past the forward edge of the hub but not foul on the aluminum seal housing. Keep in mind this is a 2 lip seal, the lip toward the flywheel only keeps dirt out sealing is done on the inboard side. Also make sure the flywheel will locate on the crank hub – it will not if the speedy sleeve is flush with the rear the crank hub. NOTE: I have found it necessary to have the inside surface of the flywheel ground to accommodate clearance requirements, but don’t eliminate the locating hub. Don’t forget to drill a drain hole in the main cap so seal is not under oil. Cut or eliminate drain tube.

Use new bolts for flywheel as well as tapered drift pins. Check for clearance of bolts and pins against seal face. You probably will have to grind them.
Clean and rough up the 2 potential sources of oil leaks at the back of the block. Camshaft closing plug and oil galley plug. Stand engine on its nose (front) and use J.B. Weld.

Carefully install seal over speedy sleeve on crank and introduce into seal housing (top half only) Check all your clearances – do this dry. No bearing lube it might foul surfaces that still need to be sealed

JB weld lower seal housing onto installed rear main bearing cap flywheel removed) Clean and 80G mating surfaces. Install 2 allan screws into seal housing halves and snug. Let set 24 hours. NOTE: Rear main cap will need to be machined to allow for clearance. Leave room for epoxy.

Remove crank and seal and inspect all bonded surfaces – insure drain hole in main cap is clear of excess epoxy. Any voids in upper or lower seal housing to block off main cap should be refilled with epoxy.
Lube mains and rods and new crank seal. Personally, I use a 50/50 mix of 20W50 and STP. Be careful at rear main as you still have more bonding to do. Clean and rough up thin aluminum surfaces of seal housing halves a small amount of JB weld is applied to both halves of the thin area of aluminum to join upper and lower seal housing – just a small smear. Now apply a small continuous bead around both halves of the seal housing to seal the seal to the housing. Lightly coat seal with lube and carefully install on crank. Drop crank and seal into upper housing. Install lower housing and main cap. Remove any excess silicone, etc.

Lastly, apply a smear of silicone seal to outer face of seal where it meets housing as extra insurance.

Tip: Anyplace on crank you might think excess JB silicone might stick should be coated with pre-lube. Use blue lock tile for fly wheel bolts and stud and bearing mount for tapered studs. Drive studs through fly wheel after fly wheel bolts have been installed.

NOTE: These tips are for the installation of the Moss seal kit only. Now is not the time to discover that your engine does not rotate without interference. I assume all of this has been verified and has been done properly.
Just prior to posting, I called the gent who owns the last engine I rebuilt (spring of 2013). He was happy to report – no leaks or drips at all after 3,000 mi. Sealing the rest of the XP engine is the topic of another discussion, but rest assured, it is possible.

Gregory S.
Columbia Restorations
(708) 715-5517
GMS Serduke

Thanks Gregory,

Please post the seal P/N, I don't recall mine being blue.

Thanks,

Jim
JE Carroll

Gregory, This is good stuff to help my confidence in doing the work. I will have to do a couple of engines that have poor /rough oil scrolls on the cranks. I hope you don't mind a little further clarification to a couple of areas:
1. Just bought my kit! : My seal is green and is a single lip design? Makes me wonder--Are there several seal designs Moss is supplying?
2. My aluminum housing has a step machined in it that will stop the seal from fitting all the way into the bottom of the recess. This step is about .060" proud of the inner face of the housing and is about 3/16" wide. The pictures shown in their instructions don't clearly show this step machining, so I wonder if its a new modification to move the seal closer to the flywheel and allow better seal placement on the redi-sleeve? Do you know if there are various housings being supplied by Moss? The fact that my kit has the step in the housing makes me believe that the instructions at figure 7. are not correct for my specific housing.
3. Can you clarify that you use the black RTV to put around the actual seal as it is fitted to the housing?
4. Finally, what did you use to seal the flywheel bolts and dowels when final fitting to the flywheel?
Richard Cameron

Here's a picture of my Seal Housing

Richard Cameron

Here's a picture of the seal they sent with my conversion kit(bought last month). There's no part number on the seal itself.


Richard Cameron

I wonder why others have not shown interest in this topic. Can it be that most have already been informed about all of the updates to the Moss Seal Conversion Kit?
Well, Just for reference, I was concerned that my seal might not be the latest version, so I contacted Mr. Jeff Zorn at LB Car Co. who researched the seal to confirm it was current. He sent me a picture of the latest one in the parts list and it appears to be the same as the one I got in my kit.
Excellent Customer Service!

Richard Cameron

I'm following the topic with interest. I have a Moss kit already installed. I do have a big leak but have not yet pulled the lump to find out if the leak is coming from the seal kit or elsewhere.

The most important thing when installing the kit is to follow the directions precisely! The folks at Moss have spent a lot of time making sure they are accurate and thorough. Do not skip steps, measure carefully, and be gentle with the speedi-sleeve.
Steve S

Richard

I have been watching this with interest, I installed the latest version of the Moss rear seal. Went thru numerous dramas in the process even to the point of having to machine my fly wheel.

All other suspect areas were addressed in the process including speedi sleeve installation and the cam shaft bearing welsh plug. The installation was proven leak free by running the engine external from the car after fabricating a device to start the lump without the starter motor installed.

Now after less than 500 miles running I have a leaking rear end dripping engine oil. Admittedly during the process the engine components were not balanced however I have no faith in the Moss product despite others indicating otherwise.

As I posted recently in my opinion the only solution to obtaining a positive result is installation of the "Chevy seal". It removes all the issues of concentricity, high revolutions at the seal face and the vagaries in block manufacture quality control, providing the machinist that modifies the block sets up correctly.

If you visit "the archive" you will locate all my previous posts indicating the history of what has occurred with my experience with the one and only XPAG I have been exposed to, to put it mildly its been a nightmare.

I hope you have better outcomes.

Graeme
G Evans

I hate to re-invent the wheel, so I turned up a dummy crankshaft journal to bolt into the rear main cap, that I use to check and adjust the oil thrower to a consistent .002" clearance. It takes care and attention to detail, but when all is properly fitted and adjusted, the original design is pretty tight.

The Moss idea is good in theory, but there seems to be too much variation in the engine castings and time-induced warpage for it to work reliably, without a great deal of machine work, including line boring.

It seems that more of the seal kits fail than succeed.

Tom Lange
MGT Repair

t lange

This might get a little wordy but I don't know how to keep it short and sweet. It seems that each engine has its own personality, with various machine tolerances on the block and some variations on cranks. I bought the Moss conversion kit because I thought it might solve some of the challenges I was facing. I thought I might try it on one test engine to see how it goes. Here's why: I'm dealing with 4 separate engines I'm trying to assemble after years of procrastination.

Like Tom, I also had a dummy aluminum crankshaft Journal machined to check and fit my oil thrower plates. With this tool in the rear main and the cap tight, I could easily insert a .005" feeler gauge in the rear cap oil scroll area. My tool od matched my crankshaft oil scroll dimension of 2.315"(all 4 cranks were in size this range). I inspected the caps and realized that all had signs of previous contact wear from the crankshaft scrolls. This information told me I would either have to close this clearance using epoxy/ JB weld process or send all of the engines to be line bored. Now, I live in Kentucky, and could not find a single machine shop who had experience in line boring XPAG to correct oil scroll clearance problems. Believe me I called everyone I thought might be able to do it. The only one that said they could happens to have the poorest reputation in town.

To make matters worse, two of my crankshafts have oil thrower scrolls that are rough from previous contact with main caps.

Finally, all of my oil thrower aluminum plates were warped so bad that there was no way for the thin gasket to close and seal them to the block. What causes this? I don't know but I don't think its entirely because of over tightened fasteners. So, it will probably happen again down the road if there's a thermal expansion reason. I straightened some, and bought new ones before I realized all of the other challenges. It was no problem to fit them closer to the crank and I could easily get around .002" clearance around the tool I had machined.

I haven't fully bought into the Moss seal conversion yet. As one can see from previous comments in this thread I question some aspects. Probably the most concerning issue so far is that it looks like I will need to machine about .100" from the rear face of the main cap so it will fit with the aluminum seal housing in place. This effectively removes about 1/8" from the scroll sealing area of the cap, so the scroll part of the cap would not be very effective if I decide to revert back to the original configuration later. Moss says their kit is reversible, Well?
Richard Cameron

Hi Guys, (This is "Verse 1")

I have some ideas that MIGHT help, but first I should explain "where I am coming from". I have never seen a MOSS kit and I only recently read a copy of the MOSS instructions ...

BUT

The MOSS kit is very similar to the kits I designed and made from 1987 as a "cottage industry". I made kits on weekends and evenings. (See photo of making retainers on dummy block.) I stopped making them in about 2001 when I realised I was spending too little time on my own cars, which include a road TC and a S/C race TC. I made perhaps less than 300 kits, selling most in Australia, Switzerland, Germany and Belgium. I never sold any to the UK but I did send a sample to "Brown and Gammons". I only sold a couple to Canada and the USA (perhaps because the MOSS kits became available soon after).

I notice the MOSS kit retainer ID (same as seal OD) looks larger but mine was 110 mm (4.331"). Could someone please inform me of the exact MOSS diameter?

Sorry, I will have to spread my input to different posts because I have only ever succeeded in uploading one picture per post. The second post, "Verse 2", follows.

Bob Schapel

R L Schapel

Bob, I measure the seal OD at 4.756". This is using a digital caliper so it may be a few thou off.
Richard Cameron

Hi again, (Verse 2)

I have attached a scan of the "Engine Assembly" side of the instruction sheet from my old kit. Notice point "F" which explains that sealant MUST be used between the cap and block (Shaded area in Fig.3) NOT just between the retainer halves like the MOSS instructions say. I realise the MOSS instructions I read might not be a recent version. ("New Improved" and "12 years of production" are mentioned on them.") Have they been updated on this point?

You can see from the red arrows I have added to the image that oil MIGHT be able to leak out if the rear of the cap is not sealed. Remember that the flat surfaces are not lapped and often have machine marks on them. There could even be machine marks which are taking oil UNDER PRESSURE from the journal!

I found that blocks and cranks do vary in length a bit. To overcome this, my instructions were to keep the seal back almost against the flywheel, spaced only by some temporary tape. (Point G and red circled note on the attached scan.) With a short block and long crank there was the risk that the seal lip might reach beyond its running surface if this instruction was not followed. This is where you chaps who have set up a MOSS seal would know if this issue applies to the MOSS kit. I know they suggest a Speedi Sleeve as a solution to this problem.

"Verse 3" will follow but might be a while because I would like to know the MOSS seal retainer ID first. (same as seal OD)

Bob Schapel

R L Schapel

Hi again, (Verse 3)

Thanks for that dimension Richard!
The MOSS seal is designed to run on the original OD of the crank flange, although Speedi Sleeve is suggested as an alternative. As the MOSS instructions mention, the running surface is narrow and most have chamfers reducing this further. I find most also have punch marks or vice marks too! I think it is a much better idea to machine the crank to create a smooth surface of maximum width and run the seal directly on that. I have attached a scan of the "..Seal .. Fitting .." side of the instruction sheet from my old kit. See Fig.1. I supplied 92 mm ID Volvo rear crank seals with my kits. In the 80s they were broader orange (silicon?) seals and I had to use certain brands which had a short lip so it did not reach beyond the running surface BUT since the mid 90s Volvo has supplied even more suitable NARROW, brown Viton seals. Unfortunately, the MOSS retainers being 4.756" ID are too big for the Volvo 4.331" OD seal. If there was a suitable seal with the MOSS tunnel size and about 92 mm ID to run directly on a machined shaft I would think that might be worth a try.

Note that on the old instructions for my kit, the drain hole was 3/8". The 3/16" drain hole in the MOSS kit MIGHT be big enough but a lot of oil sprays out the back of the journal ... and with the rotation happening, does it centrifuge and form a "vortex" of oil? Maybe? So why not make a bigger drain? DRILL IT AS LOW AS POSSIBLE WITHOUT EMERGING IN THE CORK REAR BEARING GASKET LOOP. The lower it is, the shallower the pool of oil sitting there.

Although I did not specify it in my instructions, I always remove the drain tube in the rear main cap if it is long enough for the end to be submerged. Although unlikely, I don't want crank case pressure forcing oil back up the tube as it could then fill the void around the slinger on the crank! What was that tube there for anyway?

I think that covers most of my ideas and possible solutions. "Verse 4" would probably only contain a few red herrings and unimportant bits and pieces so it might not happen! Good luck with your T-Types! They are great cars!

Bob Schapel

R L Schapel

This thread was discussed between 31/08/2014 and 06/09/2014

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