My Small Block Chevy with 360,000 miles has a slight rear main seal, I think, here is the story, when I replaced my oil pan and oil pump at 333,000 miles I put on a new rear main seal. I did the Auto-Rx thing at 343,000 miles and when I was done went back to 100% synthetic, it started leaking so I did another Auto-Rx clean phase to get the synthetic out, now I am on the rinse phase, I had oil on the trans pan and inside the dust cover for the torque converter, just some wetness, also some wetness on the back of the oil pan. I read that on a small block chevy if the rear main bearing is worn you will always have a leak, can I replace the rear main bearing and will this help. I am wondering if after the rinse phase is over this leak will stop. When I replaced the rear main seal my mechanic buddy said the rear main bearing looked fine. I am in no way blaming Auto-Rx for this leak as I have heard 2 piece rear main seals are finicky. If there is anyone with any knowledge please let me know, when this rinse phase is over it is Group III oil for me, with the 100% synthetic I could see it dripping out, the other strange thing is the leak seems to be on the back of the oil pan seal up high where it meets the transmission, maybe the leaking was because Auto-Rx was pushing out the synthetic oil, just a thought.
Rear Main Seal Leak
- Thread starter c3po
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The rear main will leak if there is excessive runout in the rearmost crank bearing. But usually by the time there is excessive runout, the damage is visible when you drop the rear main cap. If you didn't drop the crank to repalce the seal and just slid the top seal around the crank, the seal itself may not be fully seated on the crank on the side that got pushed through. (I have had the seal bunch up a little when pushing it through)I usually push them through an extra quarter inch and then pull them back to match the bottom seal. Also there may be a groove worn on the crank from the first seal and this can be a problem that requires polishing of the crank if the groove is not too deep. As for Auto-rx causing this, I doubt it. First the new seal is already cleaned with no deposits and is still pliable, not hardened like an old seal. If the crank bearings are good and there is no visible grooving of the crank from the previous seal, My money would be on the point where the top and bottom seal meet the oil pan. Or the top seal was scuffed badly when being installed.
I almost forgot, a thin film of oil should be applied to the seal edge on installation. If a pull through tool was used to install the top seal without that thin film of oil, the seal lip may have been damaged.
When the bearings [all of them] get worn, you get slop and the rear main will leak more, as the crank dances around.
Timing chain pressures will also cause movement.
And of course the seal area of the crank may be worn and grooved.
At those high miles, this is normal.
Timing chain pressures will also cause movement.
And of course the seal area of the crank may be worn and grooved.
At those high miles, this is normal.
Is it an older style two piece seal or the later one piece? If it's a one piece, you can install a wear sleeve on the seal surface of the crank to restore sealing. I did it on my Yukon's small block. It's still tight at 215,000.
Yeah, but you gotta yank the oil pan, crank main caps, transmission , and flexpate/flywheel to get a 'speedy sleeve' on there.
Originally Posted By: 03cvpi
The rear main will leak if there is excessive runout in the rearmost crank bearing. But usually by the time there is excessive runout, the damage is visible when you drop the rear main cap. If you didn't drop the crank to repalce the seal and just slid the top seal around the crank, the seal itself may not be fully seated on the crank on the side that got pushed through. (I have had the seal bunch up a little when pushing it through)I usually push them through an extra quarter inch and then pull them back to match the bottom seal. Also there may be a groove worn on the crank from the first seal and this can be a problem that requires polishing of the crank if the groove is not too deep. As for Auto-rx causing this, I doubt it. First the new seal is already cleaned with no deposits and is still pliable, not hardened like an old seal. If the crank bearings are good and there is no visible grooving of the crank from the previous seal, My money would be on the point where the top and bottom seal meet the oil pan. Or the top seal was scuffed badly when being installed.
the groove on the crank is from conventional oil coking up and causing the wear, sludge/grit is what causes the rear main to leak.
this is why 90% ASE certified mechanics recommend Valvoline oil!
The rear main will leak if there is excessive runout in the rearmost crank bearing. But usually by the time there is excessive runout, the damage is visible when you drop the rear main cap. If you didn't drop the crank to repalce the seal and just slid the top seal around the crank, the seal itself may not be fully seated on the crank on the side that got pushed through. (I have had the seal bunch up a little when pushing it through)I usually push them through an extra quarter inch and then pull them back to match the bottom seal. Also there may be a groove worn on the crank from the first seal and this can be a problem that requires polishing of the crank if the groove is not too deep. As for Auto-rx causing this, I doubt it. First the new seal is already cleaned with no deposits and is still pliable, not hardened like an old seal. If the crank bearings are good and there is no visible grooving of the crank from the previous seal, My money would be on the point where the top and bottom seal meet the oil pan. Or the top seal was scuffed badly when being installed.
the groove on the crank is from conventional oil coking up and causing the wear, sludge/grit is what causes the rear main to leak.
this is why 90% ASE certified mechanics recommend Valvoline oil!
Yeah, I did mine when the trans was being rebuilt. It was at my friend's shop, so he let me go in and install a speedy sleeve.
Also have one on the dampener.
Also have one on the dampener.
I just want too add a few things, between 54,000 miles and 100,000 miles, conventional oil, after that synthetic oil until Auto-Rx, I am not declaring victory yet, but 200 miles in to this rinse phase there is no wetness on trans pan or on the back of the oil pan. I feel this engine is clean because when I pour the oil into the engine I can here it traveling down to the oil pan, now when this rinse phase is over it is Group III oil for me, what would be a good oil to use
1)Pennzoil Platinum
2)Amsoil XL
3)Valvoline
4)Wal-Mart Super Tech
It is obvious that these oil seals do not like Group IV oil because maybe it is too slippery or the older seals do not work well with Group IV oil, this is just my guess.
1)Pennzoil Platinum
2)Amsoil XL
3)Valvoline
4)Wal-Mart Super Tech
It is obvious that these oil seals do not like Group IV oil because maybe it is too slippery or the older seals do not work well with Group IV oil, this is just my guess.
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