Yellow oil sludge on oil cap

[JeepKj03]

While adding oil to the old jeep today I noticed this yellow milky fluid on the cap and down the filler tube. I have seen it before but never really wondered what it was. I took the baffle out and cleaned it all out. Also I checked the PCV valve and hoses and everything is working the way it should. I check my fluids regularly so I know it’s not coming from the coolant, so it has to be in the oil. I figure it's was the wax in the oil, I use Castrol GTX 10W-30. Anyone know what it is?

 

[HoosierJeeper]

Normal for Mopars. My durango does it as well. Nothing to worry about.

 

[ridenby]

Mine does not do that,looks to be moisture.

 

[tjkj2002]

That is from condensation,to many short trips where the engine does not get fully warmed up to burn off the condensation that forms inside of the engine.

It's normal for all vehicles that see many short trips,just more easily seen in newer MOPAR's due to where the oil fill is(3.7's,4.7's,and HEMI's use the same oil full).

 

[JeepKj03]

That’s odd because I don’t have a short trip to work every day, hell I wish I did. It's a half an hour drive one way and it’s all 55 MPH for the most part. So I would figure that would be long enough to burn off the excess water. I would agree its condensation of some kind.

 

[valvestem]

TJKJ2002 hit the nail, it's from condensation, no worries, just wipe it off.

 

[tjkj2002]

That’s odd because I don’t have a short trip to work every day, hell I wish I did. It's a half an hour drive one way and it’s all 55 MPH for the most part. So I would figure that would be long enough to burn off the excess water. I would agree its condensation of some kind.

Well then it's time for better oil,try 5w-30 since it's the best speced weight for the KJ.

 

[ptsb5a]

I concur with TJKJ2002. Mine only does it when it's cold out. Could just be condensation that forms when the engine cools and it shows up there.

 

[LibertyTC]

Sludge city. You should check your PCV valve as well.
I had a tiny bit on my oil cap, but nothin like that.
I used Varsol, to clean the cap underneath.

 

[ShafferNY]

Yep. It's from condensation. I'm not entirely convinced it's just from short trips though, at least not on the KJ.

See. The PCV valve draws up warm crankcase air into the oil filler neck where it condenses and turns into that milky looking stuff as it mixes with the oil residue in the filler neck.

In some cases of extremely cold temperatures the condensation freezes in the PCV valve rendering it useless. Thus the TSB D/C put out revising the oil filler neck and PCV system for early KJ's such as the '03. If you look at the later models, the PCV system is different from the factory.

TSB - 2500108

 

[ShafferNY]

The 4.7L has the same PCV routing, thus a similar TSB was put out.
http://www.wkjeeps.com/tsb/tsb_wk_2500208.pdf

I couldn't find the TSB for the 3.7L, but you get the idea.

You can see how the PCV valve was removed from the oil filler neck.

 

[Ry' N Jen]

Ya know, our KJ has never had that happen!

 

[ridenby]

Got an 02,pcv valve in factory spot,no sludge,bet it is from trying to do those extended oil changes.

 

[tjkj2002]

Got an 02,pcv valve in factory spot,no sludge,bet it is from trying to do those extended oil changes.

That is another cause also,along with very humid climates.

My '02 also have the OEM PCV location and hoses and zero sludge,I use Mobil EP 5w-30 and change it every 3000miles.

 

[JeepKj03]

When I saw it I cleaned it all out the best I could and see if it comes back again as bad. I checked the PCV valve and all the vacuum lines and everything is clean and working. So I will just keep an eye on it next time I pop under the hood. If so time to change oil brand.

 

[Dave]

Yep. It's from condensation. I'm not entirely convinced it's just from short trips though, at least not on the KJ.

See. The PCV valve draws up warm crankcase air into the oil filler neck where it condenses and turns into that milky looking stuff as it mixes with the oil residue in the filler neck.

In some cases of extremely cold temperatures the condensation freezes in the PCV valve rendering it useless. Thus the TSB D/C put out revising the oil filler neck and PCV system for early KJ's such as the '03. If you look at the later models, the PCV system is different from the factory.

TSB - 2500108

Yes, I agree. And I think the plastic filler neck (being plastic) helps it condense there. I had to clean mine out last year and I do not do any short trips. I am on the interstate almost everytime I drive it. So far this year it has accumulated very little. I do my own oil changes and check it in between the changes. Meantime I changed my brand of oil to Valvoline synthetic 5w30 but I am not sure if that has anything to do with less sludge but it sure has deminished to almost nothing since. Also I do change the oil regularly. Also in the winter I shorten the oil change interval.

Dave

 

[Marlon_JB2]

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

Why are you running 10W30?

 

[kb0nly]

X2.. Why 10W??

I run Castrol GTX 5w30 year round in both vehicles, and have pretty much been using it in every vehicle i have owned. The KJ gets a very light hint of orangish color on the bottom side of the oil fill cap if i do some short trips around town, so it doesn't appear to me anything more than moisture related. However doing longer trips i never get that buildup so not sure why some do it more than others. Also if you haven't replaced your PCV valve in a while do that, even if it appears to be working, always worth a shot to make sure its flowing well as it could be dirty.

 

[RoyalDudeness]

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.

 

[twack]

i get a little here and there durring a good mn winter. But the girlfriends vw cabrio just fills with slime