rear main seal

[Drone Dog]

i had talked myself out of putting in a rear main seal. not so much the act of doing it but the part about having to cut the rear plate. also i have read a few posts on the MG TD site as well as other places saying it did not help. So i have been torn about the idea.

when i talked to the mechanic Moss had call me about the piston rings, he says he always puts one on his engines. but he did not cut the plate. instead he ground off part of the lower end of the bracket to make it fit inside the plate.

this is appealing to me if i can do it. first off, it seems easier to grind it away being it is aluminum and second i guess you do not have to remove the rear plate. i just put mine back on.

So guessing i am asking for suggestions here and to see if the grinding is possible.

i hate to go all this way and not do something i will regret later. the engine is already out....

Thanks

 

[Csarneson]

I did it on my block. I was surprised with how easy it was. To be honest, modifying the back plate was the easiest part. If you are curious I made a video on the process.

https://youtu.be/UeQ21gu1dE0

 

[steveg]

IMO if done carefully, the seal is a good thing!

Some of the seal adapters are round and some are square. I bet the round one is the one the mechanic cut the bottom off. Years ago somebody said they cut their back plate with a reciprocating saw and metal blades. I had a welding shop cut mine with a water-blaster.

I developed a technique for pinning the seal spring ends, rather than trying to hook the tiny hooks. It was practically leak-free from 2008 until last summer when I had the engine rebuilt. An advantage of this technique is it allows you to position the seal with the spring toward the engine (normal practice) rather than outward.

Careful application of Permatex Aviation Form-A-Gasket helps a lot, too. See:
https://www.pbase.com/stevegerow/image/91637854
https://www.pbase.com/stevegerow/image/97270433

 

[Drone Dog]

steve
thanks. i was just reading some old threads and saw your pinning idea. it looks like you used the round seal. how much of the plate did you need to take out? if not a lot, i would guess the seal could be cut back.

it just seems i have read a number of stories where the seals started leaking after a year or so. could be the crank was not polished enough or had some flat spots on it. could be anything.

 

[steveg]

steve
thanks. i was just reading some old threads and saw your pinning idea.

it just seems i have read a number of stories where the seals started leaking after a year or so. could be the crank was not polished enough or had some flat spots on it. could be anything.

I implied above it had started to leak when I had the engine rebuilt. It leaked a drop every couple of weeks after it got old.

 

[Drone Dog]

ok. thanks. i just ordered one. we shall see.

 

[gonzo]

I also made the conversion with plate modification plasma cut by a machine /blacksmiths shop in Livermore, CA. Such a cool just place you just had to find an excuse to get work done there. A single motor driven pulley and leather belt network on the ceiling drove all the machinery - saws, drill presses etc. If you don't want to go through the effort, I believe Tom's Toys has modified ones on exchange. They also have strengthened oil pans. And speaking of oil, the round type seal, purchased from BCS Stockton, still leaked after install. One of these days I'll get into it again and seal it up for good. Gonzo.

 

[dcarlg]

Drone Dog,
Enjoy your postings. You are making wise decisions and will be proud of the result.
I cut my back plate with a cordless jig saw, and a couple of blades. Took 45 minutes. The template was not accurate, so additional grinding was needed to fit over the installed rear seal. Also, I wrapped the seal spring onto the crankshaft and secured the ends with shrink wrap tubing before installing the crank.
I also placed the felt cigarettes as you did; cut in half, RTV in the hole and on the felt, tap into place with a punch, repeat.
I'm not a mechanic, and this was my first engine rebuild.
Good luck,
Douglas

 

[steveg]

I also made the conversion with plate modification plasma cut by a machine /blacksmiths shop in Livermore, CA. Such a cool just place you just had to find an excuse to get work done there. A single motor driven pulley and leather belt network on the ceiling drove all the machinery - saws, drill presses etc. If you don't want to go through the effort, I believe Tom's Toys has modified ones on exchange. They also have strengthened oil pans. And speaking of oil, the round type seal, purchased from BCS Stockton, still leaked after install. One of these days I'll get into it again and seal it up for good. Gonzo.

19th century overhead-belt-driven plasma cutter! Cool!

 

[steveg]

This process prevented almost all engine leaks for almost 9 years:

Paint the following areas with Form-a-Gasket: surface of seal carrier mating to block; ends of seal carrier halves where they butt; the outside of the joint between the rear main cap and block; the area around the rear cam hole.

In addition, I masked off the rear plate outside of the mating area of the block and sprayed the mating area with several coats of Permatex Copper Spray-a-Gasket. I did not use the stock paper gasket.

Also make sure you lube the sealing surface on the crank when you install the seal. If dry it'll burn up the seal.

Hylomar: install the pan gasket and little blocks on rear main cap. Also hyomar the front cover gasket.

Spring: with the pinning-method, on the bench, one can install the spring into the seal, open up the seal and place around the crank with the joint at the top and the spring toward the engine. Then one can assemble the permatexed seal carrier around the seal and screw it to the back of the engine, taking care to tighten the screws evenly so it centers on the crank.

 

[gonzo]

Steve, I now understand the crank seal pinning method and which areas on the back of the engine to coat with sealant! I installed the rear seal in-situ years ago and everything went together without issue per instruction; however, I'll definitely follow your sealing strategy next time. Curious if the split-seal is available separately? Gonzo.

 

[Keoke]

I did it on my block. I was surprised with how easy it was. To be honest, modifying the back plate was the easiest part. If you are curious I made a video on the process.

https://youtu.be/UeQ21gu1dE0

Man that was

 

[steveg]

Steve, I now understand the crank seal pinning method and which areas on the back of the engine to coat with sealant! I installed the rear seal in-situ years ago and everything went together without issue per instruction; however, I'll definitely follow your sealing strategy next time. Curious if the split-seal is available separately? Gonzo.

See Moss "Internal Engine 100-6, 3000" page. Replacement seal PN 837-095

 

[Drone Dog]

got my seal today and put in on. it showed on the website as the round version but it came in as the square one. guess it does not matter as long at it works. i bought a tap and a bit at the local hardware store. i marked my bit at 10mm. i did wrap the bit one time with duct tape so it was a little tighter in the guide bolt. just wanted to make sure i drilled straight. was not sure how critical getting those bolts in might be. as it was, i had no issues. i was a little nervouse about drilling too deep. but the drilling went fine. used compressed air to be sure i got all the filings away from the crank and cleaned it with brake cleaner.
tap worked well also. before i mounted anything i put on the top half of the metal seal and tightened the bolts up. they bootomed out before taking the seal up tight. i checked and everything was 10mm deep but i am thinking my tap did not thread quite deep enough to allow the bolts to pull the plate up tight. maybe the way this tap was made??? since i had tapped them i was not going to drill again. i had some #10 lock washers there so i put them behind the bolts. this allowed the plate to be nice and snug.

i did not use the pin method above for the spring. figured i would give the hooking a chance first. i used a (what i call) hospital clamp to hold one end of the spring and a small needle nose on the other. at first i was trying to hold the spring by the ends and it was just too hard to get them close enough to hook without the spring popping out somewhere. the nice part about the needle nose clamp is i could set the tension and so i gripped the spring about a 1/4" back from the end. doing this allowed me to hook the spring on the second try. Now i do have a set of the 10x glasses which are a must with my eye sight. also i put the spring on before the actual seal. wanted all the room i could get. rolling the spring in was a little tricky. i used a 1/2" piece of wood once i got the spring started in one spot. put the wood in so it did not pop back out. the i took my 90* awl, hooked under the spring and put the tip in the robber seal. then just slid it around the seal. it rolled right in. pushed the seal up and all was good.
of course i put some of the lubricant, actually all of it, on the seal and also smeared some on the shaft. i tried not so slide it straight up but sort of twisted it as i pushed it up and then aligned it where it was supposed to be. followed their instructions on sealing it up and bolted it up tight. when bolted up, i got just a very slight bit of sealant at the seams. not enough to wipe but i could just see the color of it.
i cut my plate with a 4" angle grinder and a cutting blade. started by trying a jig saw but whewee, i could see that being a job. as far as i got today.

Thanks for the the tips and instructions i got above. the only other thing i might add on the sealing around the cam shaft and the bearing joints... i believe i will also add some sealant around the plug at the end of the oil galley/rail. seems that is another place for potential leaks.

thanks again all.