Help me identify this leak

[Chippy]

Hi again, back with more annoying questions.

Two days ago I jacked my 05 up at the front axle, to take a look at the brakes. Today I noticed a few drops of fluid on the ground. It looks dark brown so I suspect oil… however it is right at the transmission drain bolt.

Do you guys think I have a leak up at the engine somewhere and me tilting the jeep back is causing the oil to pool at the drain bolt and start dripping? Or am I crazy?

1st pic shows the drops on the floor and second pic is a close up of the trans drain bolt.

I just changed the trans fluid with ATF so I would imagine that would be bright red. For oil I’m running 10w-30 conventional.

 

[Rickyd]

Does it smell like atf or oil? Taste?

 

[KennethS]

A small drip does not bother me. A puddle is cause for concern.

 

[Link]

Probably have a bit of a leak from the rear main seal blowing back onto the transmission.

I’m more curious about your transmission fluid choice in a manual transmission. It’s supposed to be a GL4 rated oil. Many of us are very happy with Redline MTL. The transfer case will use automatic transmission fluid.

 

[Feralkid]

Just a guess... rear of the valve cover is known to seep oil. It could also be the rear main, but when the rear main seal leaks it's usually more and will cover the rear of the oil pan mostly. Valve cover leak could run down over the top of the transmission and end up where you see it.

It looks like engine oil, but it could also be really old atf. How's the fluid look in the transfer case?

What you have to do to be sure is to clean everything up with a degreaser and then keep track of where it's coming from over the following days.

 

[Feralkid]

I just changed the trans fluid with ATF so I would imagine that would be bright red. For oil I’m running 10w-30 conventional.

Is that an auto or manual transmission?

 

[TJ Jim]

For the elephant in the room. Yes you are crazy.

Like the feral kid says, either a rear main or valve cover. Pretty common for the rear main seal to leak. Mine does. Drips a couple of drips every adventure out. 5000 mile oil changes and I never have to add any oil so it’s a slow leak. Maybe a half quart low at most.

 

[Chippy]

Probably have a bit of a leak from the rear main seal blowing back onto the transmission.

I’m more curious about your transmission fluid choice in a manual transmission. It’s supposed to be a GL4 rated oil. Many of us are very happy with Redline MTL. The transfer case will use automatic transmission fluid.

You’re right. My bad. I was thinking of the transfer case. I recently changed the trans with Redline MTL. I can’t tell if it’s engine oil or MTL then…

 

[jeepguy03]

The oil is likely from the engine, but collects there because it is the lowest point.

The 4.0L is known to leak oil from the rear main seal and valve cover. A good starting point would be to run high mileage oil. I like Valvoline Maxlife, but any high mileage oil will have seal conditioners in it. The MaxLife 10w30 has slowed down many oil leaks on 4.0L engines I've owned and serviced over the years.

 

[mrblaine]

Probably have a bit of a leak from the rear main seal blowing back onto the transmission.

I’m more curious about your transmission fluid choice in a manual transmission. It’s supposed to be a GL4 rated oil. Many of us are very happy with Redline MTL. The transfer case will use automatic transmission fluid.

I use Mopar coolant. Swepco 715 in my PSC installs, ATF+4 in the automatic transmissions either Mopar or Walmart brand, I like Valvoline brake fluid and use a bunch of it. Torco is my gear oil of choice in anything but stock axles and I'm a fan of marine rated grease for wheel bearings.

 

[Chippy]

Thanks for the comments, I hope it’s the valve cover because that seems like a way easier job than the rear main. I guess the best way to check for valve cover leaks is to shine a light at the back of the engine and see if I can see it seeping from there?

 

[mrblaine]

Thanks for the comments, I hope it’s the valve cover because that seems like a way easier job than the rear main. I guess the best way to check for valve cover leaks is to shine a light at the back of the engine and see if I can see it seeping from there?

Or just snug the valve cover bolts back down.

 

[g.hayduke]

Hi again, back with more annoying questions.

Two days ago I jacked my 05 up at the front axle, to take a look at the brakes. Today I noticed a few drops of fluid on the ground. It looks dark brown so I suspect oil… however it is right at the transmission drain bolt.

Do you guys think I have a leak up at the engine somewhere and me tilting the jeep back is causing the oil to pool at the drain bolt and start dripping? Or am I crazy?

View attachment 642116
View attachment 642117

1st pic shows the drops on the floor and second pic is a close up of the trans drain bolt.

I just changed the trans fluid with ATF so I would imagine that would be bright red. For oil I’m running 10w-30 conventional.

Looks like a possible crack in the casting just above and to the right of the drip about to drop.

 

[TJ Jim]

When you change the valve cover be aware there are spacers to keep you from over tightening and squishing the gasket out the sides. They are small silver ferrels that are easily thrown in the garbage if you’re not watching.
I’ve never found any replacements for those.

 

[OHFIVETJ]

Looks like a possible crack in the casting just above and to the right of the drip about to drop.

Possible, yes but looks more like a stain line to me as it continues & drops down the side.

 

[g.hayduke]

I have a NSG370 and a RMS leak. I never have oil dripping where the OP has it.
Seems like a lot of barking up potentially wrong trees.

To all the valve cover suggestions, possible but rarely the actual source.

 

[g.hayduke]

Possible, yes but looks more like a stain line to me as it continues & drops down the side.

If you say so. Looks more like a crack than a stain to me.

And it looks dry forward of the wet area. So how is oil getting all the way to the tail end of the transmission without getting the area in between wet?

 

[Chippy]

If you say so. Looks more like a crack than a stain to me.

And it looks dry forward of the wet area. So how is oil getting all the way to the tail end of the transmission without getting the area in between wet?

This is what I was confused about. It’s honestly pretty dry forward on the trans. I’m going to clean and degrease and see where it starts coming out. Good call though, wonder if my nail would catch on that if it is a crack

 

[Link]

You’re right. My bad. I was thinking of the transfer case. I recently changed the trans with Redline MTL. I can’t tell if it’s engine oil or MTL then…

Probably MTL. It’ll look like oil. Similar viscosity too.

Tighten the drain plug. If it doesn’t stop the leak you’ll have to pull it and wrap some teflon tape around the threads.

I had a tiny seep from the drain plug on my NSG370. Looked just like yours. Making it tighter solved the leak for me. Yours sticks farther out than mine so I’m gonna guess it’s not tight enough

 

[g.hayduke]

This is what I was confused about. It’s honestly pretty dry forward on the trans. I’m going to clean and degrease and see where it starts coming out. Good call though, wonder if my nail would catch on that if it is a crack

If it's dry forward of where it's dripping, you can pretty safely rule out RMS, oil pan, or valve cover as the source.

It almost has to be coming from the transmission or possibly (not likely) the front of the TC. I have a Rubicon and 1 of the mounting studs on the front of the TC was loose and leaking on mine. I doubt that would show up at the transmission drain plug but it might be possible.

It could be the drain plug needs to be tightened or it's possible you have a crack there.

Cleaning, drying, and careful observation will tell the story after maybe trying to carefully tighten the drain plug.