Rear Main Seal "area" Oil Leak on Rebuilt 4.0

[Mudderoy]

I know a few of you have been following my 4.0 rebuild and associated problems after the engine swap.

One problem I have been having is a oil pan leak. At first it was up front, but after Matt replaced the timing cover harmonic wheel bearing it stopped, mostly. There was a stripped out bolt that need to be replace, and tapped.

Currently I am on my 2nd Felpro one piece rubber gasket. I have managed to get the oil leaks stopped except for one, at the rear main.

Matt things it could be a bad rear main seal.

I'm not so sure.

Has anyone run across an issue with getting the rear of the pan to seal properly?

Why would a new rear main seal leak?

[prerunner1982]

I am having the same issue on mine, 2nd felpro one piece for me too. New rear main as well..... Will be interested to see what finally fixes yours.

[TimmyTXJ]

I know a few of you have been following my 4.0 rebuild and associated problems after the engine swap.

One problem I have been having is a oil pan leak. At first it was up front, but after Matt replaced the timing cover harmonic wheel bearing it stopped, mostly. There was a stripped out bolt that need to be replace, and tapped.

Currently I am on my 2nd Felpro one piece rubber gasket. I have managed to get the oil leaks stopped except for one, at the rear main.

Matt things it could be a bad rear main seal.

I'm not so sure.

Has anyone run across an issue with getting the rear of the pan to seal properly?

Why would a new rear main seal leak?

The new rear main could have been damaged while installing it. The edges of the groove at the block are sharp and can cut the seal as you're pushing it in there. I had a small leak after replacing mine but some quick dry RTV next to the RMS on either side did the trick.

You could also have a warped pan... that could explain how the leak migrated from the front of the engine to the back.

[Mudderoy]

I am having the same issue on mine, 2nd felpro one piece for me too. New rear main as well..... Will be interested to see what finally fixes yours.

See I don't think it is the rear main seal. I think the one piece isn't staying on the oil pan.

Here is a new Felpro one piece on an extra oil pan Matt brought over.

1855

I think the gasket is slipping into the pan.

[Mudderoy]

Here is one reason I'm thinking this. As you can see I RTV'd the hell out of the one I put on there prior to the current gasket.

1856

[TimmyTXJ]

Here is one reason I'm thinking this. As you can see I RTV'd the hell out of the one I put on there prior to the current gasket.

1856

Oh! You said rear main seal AREA. I thought you were talking about the rear main seal! Sorry about that. Not sure which brand pan gasket I used but it was a one-piece like that. If you do use RTV on there make sure its the quick dry stuff...oil will keep regular RTV from setting correctly.

1860

[Carves]

See I don't think it is the rear main seal. I think the one piece isn't staying on the oil pan.

Here is a new Felpro one piece on an extra oil pan Matt brought over.

1855

I think the gasket is slipping into the pan.


That would be my thoughts after the issues I had with this one.

Took me a coupla goes before I was satisfied I had the gasket sitting properly at the rear ... damn thing kept catching on something and slipping out of position.


Must have got it right eventually tho .... as it only weeps the tiniest, leetle bit now .. :D

[cantab27]

mud helps oil leaks........................true fact

[4.3LXJ]

mud helps oil leaks........................true fact

soaks then up nicely :D

[Mudderoy]

So I'm having two problems that might be related.

When I was replacing the injectors this past weekend I damaged the crankcase to air filter hose, specifically the soft rubber portion that connects to the 90 degree fitting on the valve cover. I used something to make do until I could get a proper replacement.

There was a good covering of oil on the inside of the rubber tube, outside of the hard plastic tube.

Occasionally I'll get a puff of oil smoke from the exhaust. This only happens at idle.

I'm starting to wonder if maybe something on my emissions system isn't working properly and the crankcase is being pressurized causing the oil to find a path of least resistance to escape. The only spot on the oil pan casket that isn't bolted down is that rear main seal area. It might also explain why it doesn't leak until after I drive it a while.

I have a new, factory PCV valve because it was smoking A LOT when I just had an open 90 degree non-PVC in there before.

Hmmmmmmmm

[bigjim350]

Well there is only one thing on the entire emission system that controls any crankcase pressure. and that is the pcv. Mine has never smoked bad without a PVC. Sounds like you have blow by....bummer :(

[Mudderoy]

Well there is only one thing on the entire emission system that controls any crankcase pressure. and that is the pcv. Mine has never smoked bad without a PVC. Sounds like you have blow by....bummer :(

Well Matt and I checked each cylinder's compression and they are all within spec.

While I was searching for a replacement Crankcase vent tube to air breather I found a few posts about oil in the air box. I haven't checked mine yet, but they said this could happen because of clogged or blocked emmisons. The PCV etc... clean it and the problem goes away. Certainly blow by can be a cause as well.

[4.3LXJ]

Generally the those hoses get clogged at the elbow and then start making it spit oil. All engines get at least a little blow by. For some reason the 4.0 needs both of the valve cover breathers to function right.

[Mudderoy]

Generally the those hoses get clogged at the elbow and then start making it spit oil. All engines get at least a little blow by. For some reason the 4.0 needs both of the valve cover breathers to function right.

Initially I just had the same elbow on the back as I had in the front. After it started smoking I remembered that I was supposed to replace that one in the back with a PCV, which I did and the smoking stopped. Only noticed it again recently, but now it comes and goes. Rarely see it.

I've ordered a new tube for the front so I think I'll check front and back and clean everything with carb cleaner, and make sure it's unobstructed.

I guess the next thing would be valve seat replacement.

I still wonder if this has caused the leak though.

[4.3LXJ]

Try shaking that valve. If it doesn't rattle it is clogged