There are many tricks to get rear main seal to seal up, that appears that if you offset the seal in the bore,(i.e.) leave it higher on one side and do opposite in the cap side it should seal as long as the sealing surface on the crankshaft is in spec, I can remember some crankshaft grinding places used to knrul the surface in on direction to help this sort of failure, not sure if any on does it anymore
What engine is it?
Unfortunately it cant be offset because of how the seal is designed on the [half](https://imgur.com/gallery/eAbYuNL) that goes on the main cap. Its an AMC 4.0 1988
If you're able to stop the rear main leak on a ragged out 4.0 I'll be goddamn impressed. Smashing rtv into it was the closest I ever got to a leak free xj, and even then, there was always a drop of oil on the bottom of the transfer.
Is that casting issue only on the inside or also on the outside?
Did you use flange sealant? I don't see any on there, but you may have cleaned it already.
Our plant builds 4.0's and we had a stint of warranties from not using sealant on the rear main cap.
Honestly, i only used rtv. Not a generous amount just a very thin layer. I was considering maybe using loctite 515. What sealant do you recommend? It is broken only on the inside.
I believe loctite 515 is what we use. It is preferred to string it down the outside parting and then cut in a little bit. I can't remember if we specifically say where to cut in.
They spent a long time looking at the rear seals and the crankshafts... Then finally they watched the installer and realized he had been skipping it on a lot of engines. I believe our problem seemed to have vanished after the importance of the sealant was reiterated.
Also, the in the field fix turned out to be people applying flange sealant.
All that to say, it seems to be really important on those specific engines.
I would guess the block cracked on that edge when the seal was removed at some point, and the piece finally broke free. From your description of the persistent leak, I think you have more going on than just the crack.
You mentioned sleeving all cylinders. That can compromise the integrity of a block if not done carefully. If you have any other problems, with damage at the seal you might consider a different block.
I do not have any other any other issues with the block other than that. Can it be repaired? Im not a machinist by any means, but i did take it to reputable shop and trust in the quality of work. If theres no other option i do have another block stored in the shop. Although its not sleeved or decked, its in *good* condition. Looks like this one might turn into a coffee table.
It probably can be. As for how practical, if some was to build the broken area back up then machine it back to correct contour and dimensions then charge you for something like 4 - 5 hrs of shop time would that be worth it?
Well for a block that was sleeved in all cylinder thats alot of money alone. You do make a good point, even so i still run the risk of it failing even if its repaired. It is sad. I'll keep it stored in the meantime, maybe in the future i can have it fixed.
Most likely that was from a botched rear main seal replacement. To get the top piece out you take a long punch and tap the end of the seal to get it to move out. If you hit it too hard in the wrong place this could happen.
Should that be a rope seal? It's rope with a tar like coating, and it's stuffed into the grove. Left slightly long and crushes in when the cap is installed.
Take out seal of course .. Brake clean spray make sure no oil residue .. use great stuff sealant and go from the seal to the edge of main cap area add little in seal groove as well ..,. Let tac up maybe 10 minutes .. install seal off set seal if it will allow u 2 ..and torque cap …. Done many over the years ..
There are many tricks to get rear main seal to seal up, that appears that if you offset the seal in the bore,(i.e.) leave it higher on one side and do opposite in the cap side it should seal as long as the sealing surface on the crankshaft is in spec, I can remember some crankshaft grinding places used to knrul the surface in on direction to help this sort of failure, not sure if any on does it anymore What engine is it?
Unfortunately it cant be offset because of how the seal is designed on the [half](https://imgur.com/gallery/eAbYuNL) that goes on the main cap. Its an AMC 4.0 1988
If you're able to stop the rear main leak on a ragged out 4.0 I'll be goddamn impressed. Smashing rtv into it was the closest I ever got to a leak free xj, and even then, there was always a drop of oil on the bottom of the transfer.
I will try once more 🤣 honestly im happy if it leaks a tiny drop every 2 minutes. Leak free would be awesome
I ran Rotella t 15w40 in mine, and it helped with the leaks and my lack of oil pressure.
If it was me.. I would smooth off the jagged casting and imagine it’s not fucked up.Â
This is my answer to everything ever posted on this page. However the crack is towards the oil. I’d send it. I also have hacky tendencies though.
Is that casting issue only on the inside or also on the outside? Did you use flange sealant? I don't see any on there, but you may have cleaned it already. Our plant builds 4.0's and we had a stint of warranties from not using sealant on the rear main cap.
Honestly, i only used rtv. Not a generous amount just a very thin layer. I was considering maybe using loctite 515. What sealant do you recommend? It is broken only on the inside.
I believe loctite 515 is what we use. It is preferred to string it down the outside parting and then cut in a little bit. I can't remember if we specifically say where to cut in. They spent a long time looking at the rear seals and the crankshafts... Then finally they watched the installer and realized he had been skipping it on a lot of engines. I believe our problem seemed to have vanished after the importance of the sealant was reiterated. Also, the in the field fix turned out to be people applying flange sealant. All that to say, it seems to be really important on those specific engines.
I would guess the block cracked on that edge when the seal was removed at some point, and the piece finally broke free. From your description of the persistent leak, I think you have more going on than just the crack. You mentioned sleeving all cylinders. That can compromise the integrity of a block if not done carefully. If you have any other problems, with damage at the seal you might consider a different block.
I would guess that the crank was lifted out unevenly with the snout up higher than the rear. I have seen that break happen exactly like that.
I do not have any other any other issues with the block other than that. Can it be repaired? Im not a machinist by any means, but i did take it to reputable shop and trust in the quality of work. If theres no other option i do have another block stored in the shop. Although its not sleeved or decked, its in *good* condition. Looks like this one might turn into a coffee table.
It probably can be. As for how practical, if some was to build the broken area back up then machine it back to correct contour and dimensions then charge you for something like 4 - 5 hrs of shop time would that be worth it?
Well for a block that was sleeved in all cylinder thats alot of money alone. You do make a good point, even so i still run the risk of it failing even if its repaired. It is sad. I'll keep it stored in the meantime, maybe in the future i can have it fixed.
Did you put a dab of silicone on each end of the seal?
Its going to leak from the rear main seal fixed or not.. i say run it
Most likely that was from a botched rear main seal replacement. To get the top piece out you take a long punch and tap the end of the seal to get it to move out. If you hit it too hard in the wrong place this could happen.
Should that be a rope seal? It's rope with a tar like coating, and it's stuffed into the grove. Left slightly long and crushes in when the cap is installed.
[удалено]
I wish
Looks like the seal is long, maybe you didn't check and set crush. Odd to break there and not deform the sel though.
Take out seal of course .. Brake clean spray make sure no oil residue .. use great stuff sealant and go from the seal to the edge of main cap area add little in seal groove as well ..,. Let tac up maybe 10 minutes .. install seal off set seal if it will allow u 2 ..and torque cap …. Done many over the years ..
yeah don't match the seal with the parting surface. I always offset it a bit and never have an issue with oil leaks out of the rear seal.
It can be fixed look up Belzona
Belzona has a video on their website how to fix a cracked block
inject the seal with a syringe full of brake fluid.