Help me find a coolant leak

ShimShim

ShimShim

Well-Known Member
Joined
Apr 21, 2005
Location
Charlotte, NC
I have a 2007 JKU with 179xxx miles on it. Bought it in January and have been slowly doing maintenance items (oil/filter, diff fluids, coolant flush, valve cover gaskets, etc.).
I had the cooling system flushed about a month ago when I noticed that the coolant bottle was low. I've driven several hundred miles since and I've noticed just a random drop of coolant on the ground under the jeep occasionally. Never more than a drop.

Today, I came out and found this...

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That's not a huge amount of coolant (I promise it's coolant, the camera just isn't picking up the green from this angle and with the lighting), but it's enough to be concerning. The curious thing is that the jeep has been sitting for the past five days without moving. I know the coolant wasn't there two days ago. So it sat at least three days before it decided to pee on my floor.

I poked around and looked to see if I could find the source. No evidence of obvious leaking from hoses. The thermostat appears to have no leaks. What I think is the water pump looks dry.

I did find this...

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Another angle....

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There's just a small puddle there between the valve cover and the throttle body (ignore my ignorance if that's not the throttle body, I know just enough to be dangerous). I can't see a source for where that coolant came from. I replaced the valve cover gaskets a few weeks ago so I pulled that valve cover to make sure it's not coming from there since I'm pretty sure that would be a VERY bad thing. Luckily, no coolant under the valve cover.

Under the hood, there is minor evidence of coolant below that area but nothing concrete pointing me to the source.

A look under the jeep and I found this...

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I'm not even sure what that part is that's got the coolant staining on it. And sorry for the crappy pics under the jeep. Had to juggle the phone and the light and try to get the best pics.

I could not find an obvious source from under the jeep either.

So who here is an expert and can either see something I'm missing, or knows the common coolant leak sources on the early JKU?
 
The oil cooler is under the intake, if I'm not mistaken. There's a reason they're out of stock more often than not. They ALL leak on those motors. I think the Chargers used the same motor and have the same issue. Pretty simple fix, just annoying.
 
Croatan_Kid said:
The oil cooler is under the intake, if I'm not mistaken. There's a reason they're out of stock more often than not. They ALL leak on those motors. I think the Chargers used the same motor and have the same issue. Pretty simple fix, just annoying.
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You might have to break that down like I'm 5. I'm googling and I can't find anything about the oil cooler being under the intake.

What I have found is that it may be my lower intake manifold gasket. That's a good thing cause it's a $20 part on Amazon. It also may suck because it looks like a giant PITA to replace.

Could also be a crack in the thermostat housing from what I'm reading.

Anyone else have any experience with a coolant leak in this spot?
 
Ha...I was totally thinking of the 3.6. That's my bad! The newer ones have the oil filter up top and it's part of the oil cooler assembly. 3.8s are on the front of the motor, on the RH side. I forgot...you ever forget? Happened to me :D

You're right though. Lower intake gaskets are more than likely the issue. After doing some reading, it's just a case of "when" not "if" they'll leak.
 
It's is very likely the lower intake gasket. It's not that bad of a project. Really just unbolt and bolt back. You'll need a 3/8" torque wrench, but that's about it aside from common hand tools.
 
Croatan_Kid said:
Ha...I was totally thinking of the 3.6. That's my bad! The newer ones have the oil filter up top and it's part of the oil cooler assembly. 3.8s are on the front of the motor, on the RH side. I forgot...you ever forget? Happened to me :D

You're right though. Lower intake gaskets are more than likely the issue. After doing some reading, it's just a case of "when" not "if" they'll leak.
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Whew, you had me thinking I was even dumber than I thought about engines! Good to know I'm at least a little smarter. No worries, I've can never remember shit. It's a wonder I can find my way home some days.

Jody Treadway said:
It's is very likely the lower intake gasket. It's not that bad of a project. Really just unbolt and bolt back. You'll need a 3/8" torque wrench, but that's about it aside from common hand tools.
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As far as the intake manifold gasket goes, watched a video, looks like a pain in the ass but very doable. How urgent is this job at this point? Am I risking catastrophic damage if I drive it some? It's not my daily driver, but the weather looks nice next week and I won't be able to get to the repair before next weekend.

Thank you both for your replies.
 
As long as it isn't pouring coolant out and doesn't overheat, you'll be fine to drive it some.
 
ShimShim said:
Whew, you had me thinking I was even dumber than I thought about engines! Good to know I'm at least a little smarter. No worries, I've can never remember shit. It's a wonder I can find my way home some days.


As far as the intake manifold gasket goes, watched a video, looks like a pain in the ass but very doable. How urgent is this job at this point? Am I risking catastrophic damage if I drive it some? It's not my daily driver, but the weather looks nice next week and I won't be able to get to the repair before next weekend.

Thank you both for your replies.
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Aside from a gross coolant leak out of the blue, you're fine. That front coner of the gasket tends to seep and puddle up. Not "leak" like a failed water pump.
 
Well, the intake manifold looked like ass. That gasket had been toast for a while. Got it all cleaned up, new gaskets, new belts, new coolant in the radiator and a fresh oil change. Much to my surprise, it started right up. A quick drive of about 20 miles and no check engine light. I think I did something right here. So far nothing leaking underneath either. This was the deepest I've gotten into an engine so I was a little intimidated. Hopefully it's the last time too.

This looked like ass...

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Spent a little time with the dremel and a brass wire brush and it cleaned up pretty nicely.

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Pro tip, take the fuel rail off BEFORE removing the lower manifold. It makes accessing the bolts so much easier. I removed the manifold with the rail in place and it was such a pain. Put it back together with the rail off and it was soooooo much easier.
 
ShimShim said:
Well, the intake manifold looked like ass. That gasket had been toast for a while. Got it all cleaned up, new gaskets, new belts, new coolant in the radiator and a fresh oil change. Much to my surprise, it started right up. A quick drive of about 20 miles and no check engine light. I think I did something right here. So far nothing leaking underneath either. This was the deepest I've gotten into an engine so I was a little intimidated. Hopefully it's the last time too.

This looked like ass...

View attachment 343145

Spent a little time with the dremel and a brass wire brush and it cleaned up pretty nicely.

View attachment 343142

Pro tip, take the fuel rail off BEFORE removing the lower manifold. It makes accessing the bolts so much easier. I removed the manifold with the rail in place and it was such a pain. Put it back together with the rail off and it was soooooo much easier.
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Like I said, it's just a bunch of bolts.
Nice work, dooder.
 
Ok new and surely related question. Now I've got a small leak from the radiator cap and I can hear it quietly hissing/bubbling when I stop the jeep and open the hood. Never had that before this fix. Refilled the radiator to the top after I put everything back together. Temp gauge on dash is reading normal. Fan comes on as normal. So I figure it's one of three things..

I overfilled the radiator. But the overflow tank isn't even up to max.
I'm over heating even though the temp gauge is normal.
I need a new radiator cap.

Any other possibilities? Where would you start?
 
Let it cool down. Leave rad cap off, start vehicle look for bubbles. If none, replace cap. Start with the cheap/ easy stuff first. If there’s bubbles while engine is running its leaning towards head gasket.
 
You can let it run for 15 or 20 minutes without the cap on it. Might get some overflow as the air escapes.
 
Well damn, I thought bubbles were a bad thing. It's good that my driveway has a nice incline. I'll knock this out before I go to work and see if that helps.
 
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