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Foam in oil filler neck

Old 11-23-2015, 05:13 PM
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Default Foam in oil filler neck

I just got this '00 WJ Ltd. about a month ago. I've put only a thousand miles of mixed driving on it since registering it. Two days ago, when I opened the cap for the first time, I found this in the oil filler neck of my 4.7L. When I checked again today it was gone. The GC has 105K miles on it and has been babied by the PO. Last week I took it on a 600 mile road trip to and from northern Maine. It ran the highway like a champ and gave me 20mpg, calculated through two tank-loads. Obviously, it takes a pretty mellow highway cruising to get mileage that good. Could this be a one time thing as it's never been driven like this before? Should I continue to drive it and keep my eye on T+P gauges or get it diagnosed by a pro?
Attached Thumbnails Foam in oil filler neck-foam-deposit-106k.jpg  

Last edited by Cherryokee; 11-23-2015 at 05:26 PM.
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Old 11-23-2015, 05:40 PM
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I am not a mechanic by trade. But your off to a good start by asking here. I'd keep an eye on it while continuing to collect information. I have seen this but only once in a 56 237. It's foam that forms when water is in the oil. But who knows where the water came from . It could have been temporary leak, or the beginnings of a head gasket problem.

How's the coolant level? Keep an eye on it. Keep an eye on the oil level and color. If the oil level rises and turns gray, its a head gasket.
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Old 11-23-2015, 05:57 PM
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That white stuff is water sludge formed by water condensing inside the engine by not driving it long enough for engine heat to evaporate it, like doing short trips and shutting it off before it's reached operating temp. It needed your hard run to Maine to burn it off. If it hadn't disappeared I would suspect a cooling leak like a cracked head or blown gasket.

SAE recommends trips of at least 14 miles each time the vehicle is started to keep that from forming. When the engine cools off, it pulls in moist outside air and the water vapor condenses on the metal. This doesn't happen much in desert areas. As was stated before, keep an eye on your coolant level.
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Old 11-24-2015, 12:55 AM
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Dave is right its from not being drove enough.
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Old 11-24-2015, 07:25 AM
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Thanks for easing my concerns on the cause of that foam.

Of course, the life of an "auto-chondriac" is never truly without concerns.

Stay tuned for the next installment of "What's Wrong With My Jeep Today".
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Old 11-24-2015, 12:41 PM
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If it were mine I would still change the oil and filter on it, but I'm a bit **** about that sort of thing.
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Old 11-24-2015, 04:55 PM
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you should see inside the filler neck of my ******. lol. foam partay!!!
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Old 11-24-2015, 08:19 PM
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Originally Posted by Fred/N0AZZ View Post
If it were mine I would still change the oil and filter on it, but I'm a bit **** about that sort of thing.
That is utter nonsense. This is perfectly normal for changing weather.

Would you change the coolant, and flush the brake lines as well?
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Old 11-25-2015, 01:20 AM
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Some people are OCD about their vehicles. No problem with that. That's probably why Fred's 4.7 is still perfecto as a tow rig!

Me, I fix stuff when it breaks and do normal maintenance when required. I don't have the $$$ to be ****.

The problem with that white stuff is it turns black and gummy and blocks oil flow back to the pan. Left alone long enough and it turns hard as rock.

Last edited by dave1123; 11-25-2015 at 01:24 AM.
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