Rear main seal stop leak.....

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Jun 8, 2006
My coworker just came by asking me about rear main seal leak stop products. I know nothing about them. He wants to try one before dropping $1k+ on a leaking rear main seal. Seems like it would be worth the shot to me.

Is there something out there that is a quality product and safe to use/try?
First choice would be conventional maxlife.

how bad is the leak?

If the seal is really shot or an old type material its most likely going to do nothing or just slow it.
Could try a high mileage oil like mentioned above, before recommending a stop leak product, what kind of car are we talking about here? The mileage/condition/year of the car would be helpful. In a beater than you just need to last a little longer, sure.. if its a nicer car worth fixing.. fix it.
Sounds like it is a fairly recent CRV, dunno the year but the guy thought it was around 130k miles on the odo. FWD model. I'd guess it is a 2005 or 2006. He doesn't know how long he wants to keep it.
MaxLife will likely slow it. I had a '97 Dakota with a rear main seal leak that stayed relatively dry with MaxLife. It'd leak quicker with other oils, so I stayed with MaxLife.
I wonder what the odds are that the seal is torn? The more I'm learning the more I agree that an additive won't work. The guy says the oil was changed every 5k miles using Kendall GT1 syn blend 5w20. That oil keeps things very clean. If it isn't buildup causing the bad seal that leaves seal swellers/conditioners as the only hope if the seal isn't torn.

Can a RMS tear in normal usage? he knows it is the RMS because he had his mechanic look at where a slow leak was coming from. Sounds like it leaves a few drops of oil on the garage floor when sitting over night. I would assume that is a slow RMS leak and not a fast one, right?

He just had oil changed last week so he doesn't want to try a different oil and that was when he noticed the drops on the floor. I have a bottle of Auto-RX he could try but I can't see his engine being dirty with his regimen.
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Liqui-moly motor oil saver. Do a search. It's way beyond a high mileage oil,it raises the TBN helping to extend the interval,it's an ester which is just good for many reasons and it's cheap.
Try the search function.
MaxLife would be a good first step. It does take a while to work, so your co-worker allow at least an OCI or two before declaring failure.

If MaxLife doesn't work, Liqui Moly Oil Saver seems to have a good reputation on this board. It comes in 300ml bottles that are $7-10, depending on source. It's not a one time treatment as it has to replenished at each oil change. Some say that, after thie first treatment a half bottle at each OCI works.
If it were mine, I would try the Maxlife. It is doubtful that the seal is torn.

If it is beyond seal conditioner, it is possible the sealing surface is abraded, and a replacement might not work either.
He said he wants to try Bars Leak Rear Main Seal Repair, Gumout Motor Oil Treatment or AutoRX. Maybe all since he doesn't seem to fear anything. He doesn't want to change oil and try Maxlife since the oil in the sump is less than 10 days old.

I guess I'll give him a bottle of AutoRX and see how that goes. I can't see it working I feel it is the only one that for sure won't swell anything.

EDIT: I also asked about the PCV. His mechanic said nothing about the PCV but he thinks he had it replaced around 100k mile mark.
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Originally Posted By: Clevy
Liqui-moly motor oil saver. Do a search. It's way beyond a high mileage oil,it raises the TBN helping to extend the interval,it's an ester which is just good for many reasons and it's cheap.
Try the search function.

That's what I'd try if he doesn't want to dump the oil and try Maxlife.
He decided to try the Auto-RX first since it was harmless. I can't see it doing anything as his engine should be spotless using Kendall. I stopped by his house after work to hand it off. I just happened to have my pella pump with me from doing some snow blower maintenance for a family member (snow coming saturday here in KC) and glad I did. I pulled the dipstick before adding ARX and it read high. we pumped out 1.5 quarts to get it down to full! I think this thing only has a 4.5qt sump to start with.

He seems to think this is going to be a fun experiment. He is also an engineer like me and loves to tinker. I think he is halfway wanting the ARX to fail so he can try the Bars Leak product. I told him it probably has seal swellers in it but as he said, "so what? Worst case is i'd still have to replace the RMS." fair point and I am interested to see what works so good for him.
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It might work as long as he continues to keep esters in the mix, and the seal isn't damaged. Switching to a HM oil after the A-Rx routine would be a good idea, and staying with it.
The Bars leak product never really worked well for me. I would use Maxlife(red bottle) with the liquid moly oil saver product. These two products together may work quicker then anything else that has been mentioned...
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Just an update. Surprisingly, the Auto-RX has apparently stopped the RMS leak after about 1000 miles. I can't verify the leak completely stopped but my co worker said it is no longer dripping onto the garage floor.

This makes me feel a bit disappointed in Kendall GT1 as it is also the oil I use in my Escape.
I had a hair line leak in my 2012 Hyundai Accent from PU 5w20 so I added a total of 200ml mos2 instead of 100ml and 30ml of LM Motor Oil Saver. It has almost gone away. Will continue this until oci from which I will go back to PP/PU 5w30 from now on with the mos2/motor oil saver added. It only looses about a teaspoon give or take but still.
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