Signs of Rear Main Seal Leak

[GrandW]

Could use some collective wisdom. Swapped out the break in oil, and now lots of oil leaking off the bell housing. Assumed this was the rear main seal as there's not much else there. Removed the oil pan and here's the photos. No oil on the flywheel / clutch plate. Appears to be some on the plate that holds the starter.

2nd photo is of the oil pan gasket and RTV. Visually this looks great. Checking prior threads, followed these same instructions on the rear main. Any thoughts?

viewtopic.php?f=7&t=18678&p=187024&hili ... al#p187024

[candymancan]

Wish i could help on where your leak is coming from. my rear main leaks so bad i had to add a thin sheet metal plate on the inspection cover.. and bend it into U shape to capture dripping oil to keep it off my exhaust.

I tried to replace the seal.. but i couldnt get the upper one out due to the exhaist pipe being in the way.. so i just did the lower seal and did jack squat..

Sucks i lose a quart every like 300 miles lol..


Ive heard these engines can wear a groove into the crank and even with a new seal itll leak.


I will however tell you.. that isnt the rear main seal. The rear main seal is two rubber gaskets you have to um bolt those two large bolts there. That is the main bearing on the crank shaft right there. Take that bearing cap off and youll see half of the seal on the cap and the other half is on top its the top one thats a pain to get off.

Whatever you do dont touch with your nails or scratch the main bearing and dont scratch the crank once you have the cap off. And when you put the cap back on put some motor oil all over the bearing so it isnt dry and torque it to spec.

[GrandW]

Thanks, good info. I had a few challenges with the exhaust. Ended up removing the passenger side wheel to get the oil pan out. Didn't swap the rear main seal because the oil wasn't on the flywheel / clutch plate, which most things I read said it should be. Installed a new oil pan gasket (though the old one looked good). Will have to test it next weekend. Not sure it's fixed........

Curious on the crank... completely rebuilt the engine etc. New bearings... more to come. Thanks for your input.

[candymancan]

When i tried to redo my rear main. I took off the bearing caps for the rods snd looked at them and crank journals to see how the bearings and stuff were doing. My rod bearings looked brand new still had almost no wear with 120k miles when i did it.

The piston skirts looked good and the cylinder walls looked good.. But im sure i have some camshaft issies as i hear lifter noise when the engine is cold.

But at least i know the bottom end is good from what i could see.

Wouldnt hurt if you did the same thing. Just make sure you oil it when you put the caps back on. Up to you. It wont hurt em to take em off and look. Just torque em back to spec. I think its around 50-60 ft lbs for them. But i cant remember off my head

And yea the pan is a pita to get off. Has to be contorded in positions. It helps to jack the vehicle up really high and let the axle drop down.

I think when i attemot to do my rear main ill cut the exhaust off with a reciprocating saw where it bends into that L shape. They sell replacement L shaped pipes at the autozones and stuff and i can weld so it wont be a big deal. But that damn pipe kept me from using a punch or any kind of tool to get the upper seal out.

Your picture looks dry btw. I think your leak is from the oil pan itself. If you saw my Jeep leaking youd crap yourself its that bad lol.

[letank]

I'll take a stab at it: you are correct that it is not obvious, it can be as simple as a loose oil pan bolts... you oil pan gasket looks almost non oily so that may not be your case.
Now that everything is out of the way, you may as well do it and buy 2 sets of rear main oil seal.

Loosen crankshaft caps as listed in the TSM.

And yes it is a pain to push the upper seal, last time after I pushed the first 1/4 inch off, I used one of the new seal to push the old one (hence why I get 2 seals) you can pre-oil lightly the seal to ease the extraction, the TSM says soap. Also the block edge is really sharp, once while pushing the seal the razor end of the block shaved a bit of the new seal (hence why I do get 2 seals) Pre Warm the seal to soften its texture ,obviously it is summer now, but if you live in Alaska or San Francisco, it is good to warm up the seal

Is your crankshaft steady, no fore and aft motion when pulling/pushing on the harmonic balancer?

Post edit: the dab of silicone could be a bit lean at the junction of the seal and the engine block... check the other side...

Also sometimes the leak can originate from the valve cover gasket

[GrandW]

Excellent, thank you both. Will boot it up on Saturday, and take it for smog See how it plays out.

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[GrandW]

Okay, could use a hand as I continue to pursue the leak. Pulled it all apart, everything looked good.

Which side has the "lip"? I think its photo 1, where the lip is facing the sky, and then the seal gives way and ramps downwards towards the ground (creating the shadow).

Appreciate the assistance.

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[GrandW]

1 is the answer. After replacing the rear main seal, not convinced that's it. The valve cover gaskets all look good too. Also found a thread that said the dip stick could be it, but thats solid as well. Back to wondering if the oil pan gasket is leaking somehow, and it's all flowing back to the crank, and dripping there.

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[marc]

Did you check the torque on the valve cover bolts? Thought my rear seal was shot as well. On my J10, a majority of the oil leaking was from untorqued valve cover bolts. Once they were at specs,the leaks were down 70+%

[GrandW]

Did you check the torque on the valve cover bolts? Thought my rear seal was shot as well. On my J10, a majority of the oil leaking was from untorqued valve cover bolts. Once they were at specs,the leaks were down 70+%

Were there signs of lots of oil trickling down? I will try it. New rear main, reinstalled the oil pan, it still leaks. Might also try getting an inch pounds torque wrench to make sure the oil pan gaskets are exactly to spec.

Thanks for the input.

[GrandW]

Did you check the torque on the valve cover bolts? Thought my rear seal was shot as well. On my J10, a majority of the oil leaking was from untorqued valve cover bolts. Once they were at specs,the leaks were down 70+%

Were there signs of lots of oil trickling down? I will try it. New rear main, reinstalled the oil pan, it still leaks. Might also try getting an inch pounds torque wrench to make sure the oil pan gaskets are exactly to spec. Will also double check the PCV is working right since I read something that if that's busted it can cause blow by.

Thanks for the input.

[marc]

The V8 and the straight 6 both have air filters on the breathers for the PCV valves. On the 6, it is a plastic housing inside the can housing the air filter. On the V8, it is apparently a metal housing on the oil filler. What I read is that if these filters clog they can exacerbate oil leaks. On my 6, the filter material appeared to have not been changed since God was in diapers. Guess they mimic a broken PCV valve. The part cost less than $2.00. According to the Haynes book, the V8 breather filter can be cleaned and reused unless the filter material has broken down. The hose on my crankcase air breather filter is so soft, it might not take too much vacuum to collapse it so I need to change that out too.
As for oil leaks, before I tightened the valve cover bolts, the exhaust pipe running under the back of the motor had a steady line of drips on it. Specially attractive when the pipe heated up. Wipe it in the evening and the row of drips would be back the next morning. Reduced the leaks dramatically. The smaller bolts were barely finger tight. Marc

[candymancan]

Did you check the torque on the valve cover bolts? Thought my rear seal was shot as well. On my J10, a majority of the oil leaking was from untorqued valve cover bolts. Once they were at specs,the leaks were down 70+%

Had this happen to me the last week. Was smelling burned oil and saw smoke coming from my hood.. opened it up and noticing smoke on the passenger side. Engine block is covered in oil and dripping on my exhaust manifolds and my ypipe.

I checked the valve cover bolts sure enough 4 of them were basically finger tight. Tightened em back up. But i might habe to take that cover off and reseal it. Because i think when i did my valve covers 4 years ago i use rtv. Not cork i cant remember.

Well see if it keeps leaking or not first if it does ill take it off. But yea its crazy how these bolts backed off and leaked so badly. My rear main leaks bad but NOT this bad.. iwas amazed how kuch oil was all over my block

[letank]

SNIP According to the Haynes book, the V8 breather filter can be cleaned and reused unless the filter material has broken down. SNIP

Very good point, I may add that most oil filler caps have been gutted of the filter, which is now NLA... I have been driving for over 25 years without filter... until I found out about the filter a few month ago... so I substituted one of the cut to specs Hepa filter that you can find in some vacuum cleaner filter pack

[sirrus]

SNIP According to the Haynes book, the V8 breather filter can be cleaned and reused unless the filter material has broken down. SNIP

Very good point, may add that most oil filler caps have been gutted of the filter, which is now NLA... I have been driving for over 25 years without filter... until I found out about the filter a few month ago... so I substituted one of the cut to specs Hepa filter that you can find in some vacuum cleaner filter pack

If you buy new filler cap it should come with a filter. Mine (I think Crown) did, and those things are like $10.

As for making your own - it looks way less restrictive than HEPA filter. Maybe it doesn’t matter that much, but too restrictive filter acts like a clogged one

[tgreese]

Pretty sure the oil cap filter was never available by itself. Sixes yes, V8s no. The replacements I've seen (Crown?) have a foam layer crimped-in to the cap construction.

I think the main purpose of the filter is to keep atomized oil from the crankcase out of the air cleaner. Does not take much filtering to stop oil droplets.

[letank]

SNIP According to the Haynes book, the V8 breather filter can be cleaned and reused unless the filter material has broken down. SNIP

Very good point, I may add that most oil filler caps have been gutted of the filter, which is now NLA... I have been driving for over 25 years without filter... until I found out about the filter a few month ago... so I substituted one of the cut to specs Hepa filter that you can find in some vacuum cleaner filter pack

If you buy new filler cap it should come with a filter. Mine (I think Crown) did, and those things are like $10.

As for making your own - it looks way less restrictive than HEPA filter. Maybe it doesn’t matter that much, but too restrictive filter acts like a clogged one

It is a really loose mesh , I believe that it is to protect the hepa filter . I'll add a picture latter. It is the foam that is included with some vacuum cleaners, cut to fit. I used the same on the Honda as the PCV filter is also NLA.

[sirrus]

Oh, that makes sense. I thought you used actual HEPA filter material

[GrandW]

Okay, lessons... bought an inch lb torque wrench, and that seems to have been the key. Valve cover bolts as someone had suggested were loose. Also was able to torque down the oil pan bolts with confidence and not feel like it may snap off. These 2 things seem to have eliminated the oil leak.

Much thanks to everyone who posted and the suggestions around the valve covers etc. Once finishing an rebuild, drive it a few 100 miles, then recheck the bolts where possible. Seems to be making all the difference.