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Rear Main Seal


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Tried to repair my leaking oil pan/rear main seal for the second time this weekend. I even gave the RTV 36 hours to cure fully. I used the high temp red stuff.

 

So Sunday, I start driving it and the oil pressure is running over 40 on start up until the engine warmed up, then it dropped to around 35-40 on the highway. But after about 15 minutes of driving at highway speeds, I lost it. Pressure dropped to about 22 on the highway. Which is only slightly better than what it was.

 

I'm starting to think this thing just ain't going to seal. Its not a difficult job at all and I guess I'll try it again. But I'm thinking I must be doing something wrong.

 

I found this website and the guy mentions using an anaerobic sealant that's available at the dealer. Maybe that's the problem. I should try that stuff. http://www.dailydriventj.com/forum/viewtopic.php?t=811

 

I'm prepping the surfaces right on the engine, oil pan, and bearing cap but it's just not keeping the seal.

 

I'd like to see my oil pressure stay up over 30-35 on the highway. If anyone else has any pointers, I'm all ears.

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After you check your gauge and confirm it is working and you do have a leak then you could give these a try

 

1. http://www.barsproducts.com/1050.htm

 

it's meant to stop leaking at the main seal and you're supposed to use it at every oil change, I figure if it works and costs the same as the similar amount of oil you're using then its worth giving it a try

 

2. find a double lipped main seal

 

I am having the same problem with a small leak on the main seal and I'm gonna try the 1st one if I can find it up here, if not then what's another afternoon in the garage with a 6 pack and the radio?

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After you check your gauge and confirm it is working and you do have a leak then you could give these a try

 

1. http://www.barsproducts.com/1050.htm

 

it's meant to stop leaking at the main seal and you're supposed to use it at every oil change, I figure if it works and costs the same as the similar amount of oil you're using then its worth giving it a try

 

2. find a double lipped main seal

 

I am having the same problem with a small leak on the main seal and I'm gonna try the 1st one if I can find it up here, if not then what's another afternoon in the garage with a 6 pack and the radio?

 

 

Willing to give anything a try, I'll check out the Bars stuff. I've always been hesitant on additives though, and I didn't know there was a double lipped main seal available. Thanks for the input. :cheers:

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What does the rear main seal have to do with your oil pressure? The seal just keeps oil in the engine, oil pressure would have more to do with bearing wear, pump wear etc. Maybe its just time for a rebuild! Can anyone say STROKER???

 

I think the RMS does effect oil pressure because when I first replaced it the pressure shot way up into the 40s, then it dropped again and was leaking out of the back of the oil pan. Same thing this time around.

 

I've changed the oil filter elbow along with the O-rings and upgraded to the larger SAE filter. The head was just rebuild so the head gasket is good. No leaks there. As far as I can tell there aren't any other culprits.

 

I've got a 258 crank and rods and a spare 89' 4.0 sitting in the garage. There is a stroker about to happen,,,,I just need some more bling $$$$.

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What does the rear main seal have to do with your oil pressure? The seal just keeps oil in the engine, oil pressure would have more to do with bearing wear, pump wear etc. Maybe its just time for a rebuild! Can anyone say STROKER???

 

I think the RMS does effect oil pressure because when I first replaced it the pressure shot way up into the 40s, then it dropped again and was leaking out of the back of the oil pan. Same thing this time around.

Nope.

 

When I rebuilt an '88 XJ for my ex-girlfriend and drove it from the east coast to Montana, the rear main seal let go halfway across Pennsylvania. The oil pressure didn't change.

 

You're looking at bearings, in addition to getting the RMS to seal. Are you using the seal with the double wiper?

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The only relation I've ever heard of between the RMS and oil pressure is from my 88. After my RMS blew and drained most of the oil out of my engine on the freeway, the oil pressure went to 0 when I stopped at the next light and the engine went to idle.

 

 

You might get lucky and only need to clean up the electrical connection at the sending unit.

 

Is your engine still spewing oil out the back?

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What does the rear main seal have to do with your oil pressure? The seal just keeps oil in the engine, oil pressure would have more to do with bearing wear, pump wear etc. Maybe its just time for a rebuild! Can anyone say STROKER???

 

I think the RMS does effect oil pressure because when I first replaced it the pressure shot way up into the 40s, then it dropped again and was leaking out of the back of the oil pan. Same thing this time around.

Nope.

 

When I rebuilt an '88 XJ for my ex-girlfriend and drove it from the east coast to Montana, the rear main seal let go halfway across Pennsylvania. The oil pressure didn't change.

 

You're looking at bearings, in addition to getting the RMS to seal. Are you using the seal with the double wiper?

 

 

I put in the single wiper seal. I guess this is going to move my stroker to the left on the calendar. The motor still runs awesome though. I'm about 2 weeks from clicking over 200K. Sitting at 199,300ish.

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Oil isn't spewing, just a slow leak. Not sure how it leaks on the highway under pressure. Kinda scared to open the door and look, haha. But when I stop after about 5-10 minutes there will be a puddle starting to form.

 

I think I'm going to go to Slaughterhouse or Bandimere Speedway and just run the H$#% out of it, maybe it'll let loose on me, then the wife will have to let me do the stroker. My luck, the engine will hold fine and I'll break something else.

 

I walk by the 258 crank just sitting in my garage every morning. :drool: Its day will come!!!! jamminz.gif

 

 

OK, to summarize:

The RMS can effect oil pressure but isn't the main factor. Most likely it is sealing enough to keep near constant but slightly low pressure. The main reason for the low pressure would be the bearings or the pump itself. Also, considering the fact that it has darn near 200K on the odometer and engines with this much mileage just run low.

 

Does anyone else with 200K plus have low oil pressure? Is this acceptable for a good smooth running but high mileage engine?

 

Thanks for all the input so far!! :cheers:

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My 88 generally doesn't show over 25 psi at any time. Could be the gauge, sender, or the 200k miles on it. Don't know, don't care. As long as it isn't 0psi :ack: (happened twice now, once from the rms leak and once due to a fram oil filter :fs1: ).

 

I'm not saying yours couldn't be better, but it's possible that you're over-thinking it. :D

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Oil isn't spewing, just a slow leak. Not sure how it leaks on the highway under pressure. Kinda scared to open the door and look, haha. But when I stop after about 5-10 minutes there will be a puddle starting to form.

Oh, you'd know. When the RMS let go on the ex-GF's Cherokee, the oil hit the exhaust and I trailed a smoke screen all the way from central PA to Montana. It didn't all burn up, either. It poured out so fast that I had to wash an oil slick off the rear hatch at every stop. I bought a CASE of Wal-Mart's house brand oil in PA, and there was none left when I got to Montana.

 

OK, to summarize:

The RMS can effect oil pressure but isn't the main factor. Most likely it is sealing enough to keep near constant but slightly low pressure. The main reason for the low pressure would be the bearings or the pump itself. Also, considering the fact that it has darn near 200K on the odometer and engines with this much mileage just run low.

Sorry, I disagree. The RMS can affect oil pressure only if it dumps ALL the oil and the pump is sucking air.

 

Does anyone else with 200K plus have low oil pressure? Is this acceptable for a good smooth running but high mileage engine?

My '88 Cherokee (mine, not the ex-GF's) is currently a bit over 280,000 miles. The RMS was replaced once, maybe 100k back. Oil pressure started to look a bit low at around 175,000 with conventional 10W40, so I changed to full synthetic 5w50 and it's okay. Runs about 40 on the highway and idles around 20. When it was new, it ran 50 to 55 psi on the highway and idled at about 25 psi.

 

The factory spec for oil pressure is 13 psi at idle, and anywhere between 37 and 75 psi above 1600 RPM.

 

How's your CCV system? The RMS isn't pressurized by the oil pump and circulation system, but if your CCV system is clogged the crankcase may be under pressure from blowby, and THAT can force oil out through even a good RMS.

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Only way to be sure about the pressure is to put a mechanical guage on it. Probably just due to the higher mileage. What are you running for oil?

 

Have to agree with dasbulli though. RMS does not have high pressure oil at it to begin with. Ever notice the ring that sticks up between the rear bearing journal and the RMS journal?

 

How much RTV did you use on the rear cap? All you need is a slight dab. And you had it torqued before you let it cure, right?

 

With the constant leak, you might have excessive blow by causing high crank case pressures. Some guys here have been doing a CCV conversion to help eliminate this issue.

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OK, to summarize:

The RMS can effect oil pressure but isn't the main factor. Most likely it is sealing enough to keep near constant but slightly low pressure. The main reason for the low pressure would be the bearings or the pump itself. Also, considering the fact that it has darn near 200K on the odometer and engines with this much mileage just run low.

 

Does anyone else with 200K plus have low oil pressure? Is this acceptable for a good smooth running but high mileage engine?

 

Thanks for all the input so far!! :cheers:

 

 

We have 2 jeep 4.0's:

90XJ 194000 mi, 80+psi cold, 35+psi idling hot, 50+psi on highway, 10W30 full synthetic, all pressures on autometer mechanical OP gauge (stock electrical gauge reads +-10 psi)

 

93 XJ 225000 mi, = 5-10psi as above, running 10w40 synthetic blend.

 

I'd look at a worn oil pump, or worn bearings.

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Well, I woke up this morning and there was no oil on the driveway under the jeep. I guess it decided to seal up.

 

I'm running regular Mobile 5-30W, ILSAC GF4 certified oil. CCV is all good. When I rebuilt the head, I cleaned out the inside of the valve cover also. I spent a day at the JY pulling all good vacuum hoses and lines. I got the factory service manual for the CCV and ensured all the lines were running were they were supposed to minus the line that runs through the factory air box. I'm running a cone type air filter and I punched a hole in my intake hose and ran that particular hose into it. So there's no clogging anywhere. I don't notice any blowby, and I believe I've got all the lines going where they are supposed to go.

 

I'm kinda of a purest with mechanical things....Pete, you're probably right, maybe I'm over-thinking it,,,I just believe if its not abused and maintained correctly then the darn thing should work right,,,,right? :smart:

 

I guess I'll be good with the oil pressure around 22 on the highway based on ya'lls input. Looks like the motor, although it runs great, is a little wore out on the inside. I could see the factory cylinder hone marks on the cylinder walls when I did the head so I figured the thing was in pristine shape.....guess the bearings are the culprit.

 

Thanks for the input! :cheers:

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  • 3 weeks later...

UPDATE!!!!!! :banana: Here's my recommendation for oil filters!!!!

 

I changed my oil yesterday and got great results! I had already ditched the Fram filters and went with Purolators. I had first put in the Purolator with the gold colored textured finish so it was easy to spin by hand ( I don't remember the p/n). Yesterday I put in the Purolator Premium Plus p/n L30001. Its the white smooth textured one. My oil pressure shot up to 22 at idle and 45-50 above 2000 rpm prior to being fully warm, the settled in at 37-42 or so when warm over 2000 rpm on the highway.

 

I'm stoked, now the oil pressure gauge actually reacts to rpms when I rev the engine and no longer sits as 18-20 regardless of rpm.

 

So with the Purolator L30001 I am getting almost double the oil pressure. This filter obviously flows more, I can't say if it is actually filtering any better. But more oil flow is better!

 

So my vote for oil filters from here on out is the L30001!

 

I'm happy, I'm going to buy some beer tonight ---- woohoo!!! image_209027.gif

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