when do i HAVE to change a rear main seal?

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391
my 03 hummer h2 with a 6.0L V8 LQ4 with 250,000 km on it seems to have a rear main seal leak or a oil pan gasket leak. Most likely it is a rear main as i noticed more people on the hummer forum having a rear main leak.
I noticed the leak about a year ago and it barely made a difference on the oil level, and then winter came so i never really looked or checked but everytime i would check the oil level it was always in a good position.
it is summer now, and i guess maybe the hot weather is making the leak worse but i notice more oil under my vehicle now compared to before.
i recently checked the oil level and it was about 1 quart low so i quickly filled it up. i last had the oil change in february and i have already put 5000 ish km's since february so it seems to lose about 1 quart over 5000 km or 4 months ish.

the thing is that i am parking this vehicle most likely by next january, and i dont want to spend $1200 on labor etc.

so i wanted to ask, what are the chances that if it is the rear main, that it just completely blows out and drains all the engine oil out within seconds?
my plan rn is to just keep it like this and keep adding oil and if i notice that i am adding way too much or if it starts to leak way too much then i obvs have to do something about the seal.

i was also thinking of running blue devil rear main sealer or at 205 resealer but i also heard that gm engines use a teflon rear seal which wouldn't be able to be "bettered" by stop oil leak products. so i am not too sure about that, any way i can actually find out what seal i have in the truck? its a 2003 and it is a 6.0 LQ4 engine unless I am mistaken on the engine model.


thanks!
 
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26,121
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MA, Mittelfranken.de
I cant say if this engine uses a teflon seal or not but regardless I would stay away from strong solvent brews like ATP, the problem is when you swell one seal you swell them all. While unlikely it is conceivable it turns into a leaking nightmare.
Chances are it will not blow out just leak worse. If you only need it for 6 more months you could try this, it may or may not help but it seems to be the least aggressive.

 
What motor oil are you using? If it’s 5w30, you might want to change to 5w40 or 15w40 for the summer. While parked, the oil level in the pan is well below the seal level. You would be losing it while under way and any drips you saw while parked would just be residual oil that already escaped from the seal area. I’m running 5w40 on my 200,000 mile 6.0 during the summers anyway.
 

jalikaria24

Thread starter
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391
I cant say if this engine uses a teflon seal or not but regardless I would stay away from strong solvent brews like ATP, the problem is when you swell one seal you swell them all. While unlikely it is conceivable it turns into a leaking nightmare.
Chances are it will not blow out just leak worse. If you only need it for 6 more months you could try this, it may or may not help but it seems to be the least aggressive.


Ahh gotcha thanks! How does this compare to blue devil rear main sealer then? Or is blue devil a solvent as well

Thanks
 

jalikaria24

Thread starter
Messages
391
What motor oil are you using? If it’s 5w30, you might want to change to 5w40 or 15w40 for the summer. While parked, the oil level in the pan is well below the seal level. You would be losing it while under way and any drips you saw while parked would just be residual oil that already escaped from the seal area. I’m running 5w40 on my 200,000 mile 6.0 during the summers anyway.


I’m running a Mobil 1 5w30. Will for sure goto HM on next oil chance. I thought it wouldn’t made a difference if I change viscosity becusse it is most likely leaking when the engine oil is warm and correct me if I’m wrong but I doubt the viscosity diff would stop it? I posted about changing viscosity before and seems like most people said just go 5w30 hm
 
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11,691
Location
Illinois
A box full of cat litter under your parking spot and keep an eye on your oil level.

By parking in January, I presume you mean no longer driving this vehicle...
 
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5,009
Location
Southeast
rear mains tend to worsen over time. The longer you let it go, it can leak for a long long time, but everything under there behind it will be coated it in and less fun to work on. Oil is cheap, getting stuck without it is not, idling in your own oil stink if it gets on the exhaust is not fun. If you like the vehicle, I start looking for other things which might need to all be done while it’s down for repair, and save up for the repair. 6 months?
 

jalikaria24

Thread starter
Messages
391
A box full of cat litter under your parking spot and keep an eye on your oil level.

By parking in January, I presume you mean no longer driving this vehicle...
Yeah exactly parking in January and then will prob do the repairs then by myself when I’m free
 

jalikaria24

Thread starter
Messages
391
rear mains tend to worsen over time. The longer you let it go, it can leak for a long long time, but everything under there behind it will be coated it in and less fun to work on. Oil is cheap, getting stuck without it is not, idling in your own oil stink if it gets on the exhaust is not fun. If you like the vehicle, I start looking for other things which might need to all be done while it’s down for repair, and save up for the repair. 6 months?


Yeah I’ll repair it in the future but when I’m free and can spend weeks on it since I won’t be driving it anyways! So you tbink I’ll be fine until then?
 
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9,122
Location
Marshfield , MA
A qt in 5k miles is no big deal. Buy cheap oil and keep a few qts in the vehicle. Yes it will get worse. Possibly, just possibly is the leak from above or forward. That is the lowest point that oil will flow to. Anyway, its a manageable leak. 😃
 
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17,593
Location
...
Most people don’t mess with the rear main seal until something else forces their hand like pulling the transmission. Then it makes sense.

In your case with 1 quart/5000 miles, I wouldn’t worry about it
 

Astro14

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13,234
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Virginia Beach
The rear main seal on my old (1990) Toyota 4Runner began weeping at about 90,000 miles. As the truck aged it got worse. But fixing it meant a ton of work, including removing the transfer case. I let it go...

At 250,000 miles, it was using about a quart every 1,500 miles, most of that out of the seal. Occasional spots on the ground when parked.

Now, at 300,000 miles, in the hands of its new owner, it probably leaks even more...

and I still wouldn’t fix it.
 
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13,232
Location
North Carolina
You change it when its leaking too much to drive on long trips, or in the case of a manual transmission, it contaminates the clutch lining.
 

jalikaria24

Thread starter
Messages
391
does it have a chance of blowing out and draining all the oil? or is that very very late?
even if it blows wouldnt the metal between the transmission and engine act as another seal so that all the oil doesnt leak out?
 
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