Yellow oil sludge on oil cap

[ThunderbirdJunkie]

The last time that happened to dude it was a bad head gasket leaking coolant into the oil. Check your dip-stick for water bubbles as well to be absolutely sure you are not leaking coolant into the oil. No other vehicle of dude's has ever shown that milky deal; only the one that had a bad head gasket. I do not have that on my fill with about 70 thousand miles and never seen that- just be a little cautious.

Just FYI, this is common on all Mopars with the huge oil filler. It happened back when ThunderbirdJunkie first got his KJ but it hasn't happened in about 75,000 or so.

No leaking head gasket here, either

 

[JeepKj03]

Well there are a few reasons why I use 10W-30 instead of 5w-30. The engine has 110k miles on it so the clearances have opened up so it can have heavier weight oil can work when she starts up. When it warms up the oil becomes 30 weight anyways. Plus the owner’s manual states I can use 10w-30 down to 00F and that does not matter anyways because she gets plugged in when the snow can start flying. Everyone does their own thing for a reason.

 

[MickityMike]

Use 5W, turn key, pause for a few seconds before starting: Problems solved.

 

[RoyalDudeness]

Use 5W, turn key, pause for a few seconds before starting: Problems solved.

Dude is curious; what does that do; the turning the key and waiting a few seconds?

 

[kb0nly]

Dude is curious; what does that do; the turning the key and waiting a few seconds?

Allows the fuel pump to build pressure, same thing on the Pontiac Montana we had, in the winter time it would crank longer before starting if you didnt give it a three count after turning on the key to let the fuel pressure come up.

 

[ChiefRudy]

I noticed the yellow sludge in both my engines. My 06 KJ b/c i drove to work 5 miles one way to work everyday and with the 02 KJ the the Previous owner never took care of it the right way and there garage never cleaned out the oil spout from the looks of it. (the sludge catcher thingy was fused to the inside of spout from the slug and took me an hour to get to get it loose and out). After Switching both to mobil-1 full synth there is now only a super thin layer of yellow sludge on the cap to not being there at all.

There's my two cents

 

[candpliberty]

My mom (may she rest in peace) drove a Chrysler Sebring and I religiously used Castrol Syntec with excellent results. It's touted as a oil good for engines that never reach operating tempurture. She put 30k miles on her car in 8 years. No sludge, no crud, clean as a whistle.

 

[ThunderbirdJunkie]

Curiosity...what engine was in that Sebring?

If it was a 2.7 that is impressive.

 

[ShafferNY]

Use 5W, turn key, pause for a few seconds before starting: Problems solved.

All that does is pressurize the fuel system. I don't see how it would help anything.

I've noticed this with every 3.7L we've had.

Why are you running 10W30?

My uncle, who was a fleet service manager for Verizon, use to always run 5w-30 in his personal vehicles during the winter, and 10w-30 in the summer.

According the the owners manual in my 2003 KJ(chart below), 100* is about the cut off point for 5w-30, where as 10w-30 is still acceptable. Like wise, 5w-30 is better suited for colder weather.

Oddly enough, the oil viscosity chart in our '06 KJ owners manual states 5w-30 is the "perfered" viscosity for all temperature ranges. While 10w-30 is still acceptable for temperatures 0* and above. It appears this recommendation changed in 2004. Go figure.

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[belvedere]

Oddly enough, the oil viscosity chart in our '06 KJ owners manual states 5w-30 is the "perfered" viscosity for all temperature ranges. While 10w-30 is still acceptable for temperatures 0* and above. It appears this recommendation changed in 2004. Go figure.

As to why Chrysler changed their recommendations, I don't know. But, I do know this: oils have definitely improved. 10-15 years ago, I wouldn't have felt comfortable running 5W30 in 100*+ temps. Now, I don't think twice about it.

 

[RoyalDudeness]

Allows the fuel pump to build pressure, same thing on the Pontiac Montana we had, in the winter time it would crank longer before starting if you didnt give it a three count after turning on the key to let the fuel pressure come up.

Dude thought it may have had some secret thing to do with the oil circulation since it is the topic. Dude always waits more than a few seconds before starting since dude has adjustments to make to the sound system first. With the oil-n-sludge deal- if you use synthetic you have a lower tendency for sludge even with known troublesome engines like that two-point-seven and the magnum edition- both which are horribly bad motors. Also on the main topic dude has no discoloration on his oil areas.

 

[sleeve]

I have this build up every winter.

It's very normal for the KJ. It's been doing it for nearly 8 years now and the Jeep keeps on going. Just clean out the crud every week or so and don't worry about it.

As to why it happens:

Chimney effect due to the crappy plastic oil fill neck. Hot oil vapor rises and gets trapped in the oil fill neck. Cooling because of the engine fan blowing cold air... Then the water vapor condenses with the oil and sticks to the plastic walls. Building up into the goo puddle.

 

[Ry' N Jen]

I have this build up every winter.

It's very normal for the KJ. It's been doing it for nearly 8 years now and the Jeep keeps on going. Just clean out the crud every week or so and don't worry about it.

As to why it happens:

Chimney effect due to the crappy plastic oil fill neck. Hot oil vapor rises and gets trapped in the oil fill neck. Cooling because of the engine fan blowing cold air... Then the water vapor condenses with the oil and sticks to the plastic walls. Building up into the goo puddle.

In the three years and 27 days that we've owned our KJ, it has never
happened with our Jeep.
I wonder why?

 

[Marlon_JB2]

2.7L is a great engine now.

Used to be craptacular though...

 

[sleeve]

Mechanical Engine fan?

 

[ridenby]

Mechanical Engine fan?

Yes,I am a fan of mechanical engines. Thanks for asking.

 

[sleeve]

Sorry,

I was asking: Those that do not have condensation during the winter months, if their KJ's were equipped with the mechanical engine fan from the HD cooling package. The reason I ask this is that my theory of the chimney effect can be shot down or reinforced.
I believe this phenomenon occurs when the mechanical fan pushes cold air over the oil fill tube prior to reaching full operating temperature. This is what allows condensation to develop in this particular region of the motor. Specifically it occurs when the engine is in the process of warming up but has not achieved full operating temperature. In this state, water vapor is able to travel to the chimney / oil filler where it’s immediately met by the cold air forced on the filler neck by the mechanically driven fan. At this moment of near operating temperature condensation forms in the filler tube. Once the engine achieves full operating temperature, radiated heat can warm the oil fill neck to a point where no more condensation occurs. But for roughly fifteen minutes, the 3.7L engine appears to be a condensation generator.

It’s my theory and it has yet to be proven. Some insulation or a wind blocker fixed in front of the filler tube might be a valid testing mechanism to debunk my theory.

 

[MickityMike]

Sorry,

I was asking: Those that do not have condensation during the winter months, if their KJ's were equipped with the mechanical engine fan from the HD cooling package. The reason I ask this is that my theory of the chimney effect can be shot down or reinforced.
I believe this phenomenon occurs when the mechanical fan pushes cold air over the oil fill tube prior to reaching full operating temperature. This is what allows condensation to develop in this particular region of the motor. Specifically it occurs when the engine is in the process of warming up but has not achieved full operating temperature. In this state, water vapor is able to travel to the chimney / oil filler where it’s immediately met by the cold air forced on the filler neck by the mechanically driven fan. At this moment of near operating temperature condensation forms in the filler tube. Once the engine achieves full operating temperature, radiated heat can warm the oil fill neck to a point where no more condensation occurs. But for roughly fifteen minutes, the 3.7L engine appears to be a condensation generator.

You wouldn't need the fan to push the cold air - it's already going to be cold around the neck when you first start up prior to reaching op temp.

It’s my theory and it has yet to be proven. Some insulation or a wind blocker fixed in front of the filler tube might be a valid testing mechanism to debunk my theory.

Nope. This would only tell you if insulation helps, not if the fan is the culprit (because it's not).

 

[sleeve]

Please explain then why this happens on some KJs and not others.

 

[ridenby]

Please explain then why this happens on some KJs and not others.

Why am I blessed with good looks and brilliance? Good genes? Luck? Who knows. I do think type of oil,maybe change interval. Maybe having them pluged in,low heat,just enough to create condensation,not enough heat to "burn"water vapor off.