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Strange residue near oil cap?

3191 Views 16 Replies 8 Participants Last post by  bluejunior
I recently changed my oil and while doing so I noticed there is some kind of whitish residue on the cap and surrounding areas. Any idea what it is? Jeep is 2000 Cherokee Sport 4.0L. See pics.

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I have a very good idea what it is. It looks like what happens what coolant and oil mix. Since you have a 2000, there's a common problem with the cylinder head cracking, allowing coolant to get into the oil. After a while, the oil will start to look like that.

Please google "0331 Cylinder Head" and you will find a host of information regarding the issue. In short, it looks as though you will at least need a brand new cylinder head. However, since you may not know how long this issue has been present, your entire motor may be shot.
 

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If you drive lots of short trips, that is simply normal condensation, and the cylinder head is probably just fine. If most of your driving allows the engine to fully warm up for 10-20 minutes or more of full temperature driving, that might be coolant in the oil, especially if you often find the coolant level low.

Before you consider any type of remedy or repairs, you need to have a proper diagnosis of the observed symptoms. Send an oil sample to Blackstone Labs.
 

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It's probably the 0331. Tim's right it could be condensation. If it were mine I'd probably pull the valve cover and see if it's just around the cap (meaning it's probably just condensation) or if all the oil up there looks like that (probably 0331) but sending it to a lab to test for coolant is certainly a surer way.

Short version if it is the 0331: If you've caught it early then replace the head with a 03+ 4.0 head out of either a TJ or a WJ as soon as you can, then flush the cooling system a couple times and do a couple of oil changes with a good treatment like seafoam added in a pretty short inteveral (1000 miles or a couple months, depending on your usage). That should get most of the crap out and head off larger issues. It's a slow death but long term coolant mixing with the oil through will cause all sorts of problems with the block, cooling system and with oil pressure.
 

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Did it just start since the last oil change? Are you loosing coolant? Sure looks like you might have a problem with the head. First thing I would do is follow CJ7-Tim's advice and send a sample off for analysis. Good Luck.


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Discussion Starter · #6 ·
Yes I am loosing coolant. I've been wondering why I had to keep filling it up. Is there a chance that it could be something like the head gasket? How can I get the coolant out, would an oil change do the job? Also, what damage can the coolant do to the engine when mixed with oil?
 

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Yes I am loosing coolant. I've been wondering why I had to keep filling it up. Is there a chance that it could be something like the head gasket? How can I get the coolant out, would an oil change do the job? Also, what damage can the coolant do to the engine when mixed with oil?
Given the year of your jeep, which is very prone to the head itself cracking, and your symptoms it's unlikely to be just the gasket.

The coolant will damage your oil's ability to lubricate properly and drop your oil pressure. It will also rust your engine block eventually. Also, the cross contamination will cause a lot of extra gunk in your cooling system. You can somewhat compensate by increasing the frequency of fluid and filter changes for oil and coolant and using a thicker oil. It will work as it is for awhile, but this will eventually kill the engine.

The only real thing to do is replace it with an appropriate head (a TUPY 0331, which is better cast and doesn't crack) from an 03-06 Wrangler or 03-04 Grand Cherokee. hese are not overly expensive but can be hard to find depending on your area. Then use a very fast oil change interval for 2-3 changes to get the crap out and flush your cooling system. T

Even if you think it's just the gasket, that weak head is an issue and it's the exact same amount of work to replace the head as it is to replace the head gasket.
 

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it will eat the Babbitt bearings, since oil and water tends to make mayonnaise that tends to not lubricate very well. Before you get the coolant out you need to fix the issue. Like what has been said the heads crack worst case. head gasket would be the lessor. But since this is rather well documented issue. The only real fix is to remove the head and inspect/ replace. Trying to get the coolant out before the fix wont work, chasing you tail at that point.
 

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Discussion Starter · #9 ·
Thanks, guys. I wasn't denying that it was the head, just wanted as much info as possible. My plan is to find a head from a junk yard from the models listed above. I've had to remove an exhaust manifold before, and that's my biggest concern, because I don't want to snap the bolts. Is there a good way to prevent that from happening, and if they do break, would I simply just re-drill and tap the holes? Given that I will be opening up the engine, is there anything else I should look into while I've got it all opened up?
 

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Thanks, guys. I wasn't denying that it was the head, just wanted as much info as possible. My plan is to find a head from a junk yard from the models listed above. I've had to remove an exhaust manifold before, and that's my biggest concern, because I don't want to snap the bolts. Is there a good way to prevent that from happening, and if they do break, would I simply just re-drill and tap the holes? Given that I will be opening up the engine, is there anything else I should look into while I've got it all opened up?
Best thing you can do is start soaking them all in penetrating oil NOW. once a day until you actually do the job. I keep the can in my cupholder to remind me for that sort of thing. The overspray may smoke off the exhaust manifold, but that won't do anything but smell bad if you keep it to a minimum.

Other than that, yeah you can drill them out but not very large. It would be best to try an extractor first if one breaks or else drill and retap it at the factory size. Those bolts don't have an insanely high torque spec and that'll help prevent you from getting into part of the block you shouldn't.
 

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Few days of penetrating fluid, and if you run the engine up to operating temp and give it some skinny pedal and immediately after start unbolting exhaust and intake manifolds, chances are the bolts will come out just fine.
That is, if the engine is in a condition it can be run for 10-15 minutes at high idle.

As for the sludge you have on the oil filler cap, don't expect the worst scenario as the primary suspect. Sludge build- up like that - and even way worse than that - is 100% normal in cool/ cold climate during winter if doing short commutes. It does happen to some extent in warm climate as well, but it's usually not close to as evident as it is in cool climate.
There is always moisture that accumulates especially inside the valve cover(s) - hot engine and warm air cooling down will condensate into water. When the engine slightly warms up, water only partially evaporates and the water vapour forms the sludge on the filler cap and inside valve cover(s). If you run the engine long enough, all the moisture will be evaporated and the sludge will disappear.


Before pulling the cylinder head or buyng anything, make sure you actually do have a cracked 0331- head or a bad head gasket. There's no point in wasting money on parts you don't need, or doing maintenance you don't have to.
 

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Discussion Starter · #12 ·
Again thanks for the info, I hope its not a cracked head, but I fear that given the symptoms it is. I fill my coolant overflow tank to "full" and then after a couple days of driving (could be more or less) I check it and its empty. That coolant is going somewhere!
 

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Mine has the disappearing coolant but much more slowly than yours. No real signs of milkshake oil, but low oil pressure - especially in summer - and worn main bearings. Didn't notice the low pressure until the first oil change after purchase, so the damage was already done but disguised with thicker oil. On the bright side, it has gone over 30k miles since then. I'm just going to roll with it until it goes and drop in a stroker.
 

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Discussion Starter · #14 ·
I know it's been a while, but I finally got the time to do the job. I have the head removed and its covered with gunk. Now I just have to clean it up and inspect for cracks. Any tips on what to use for cleaner, and how to inspect for cracks? Thanks.
 

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For really thick gunk I use xylene, because it works well and I have it sitting around. Don't let it get to anything rubber or plastic though. Xylene thinks that stuff makes a good snack.

For thinner layers your basic grease and wax remover helps a lot, it just sometimes takes a few soak and wipe rounds.

Just don't use a steel wire brush on a machined surface or anything damaging to steel like that and you can pretty much use whatever evaporating solvents you happen to have handy on steel. Nylon brushes are good, too, if there's big chunks.
 

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Dish soap on a rag and some elbow grease will handle most crud just fine. Dawn seems to be better at cutting automotive grease/oil than the other brands if that makes a difference for you.

Cracks typically occur between 3 and 4, but they may not be visible. The only sure way is to have a reputable machine shop magnaflux it. They blast it with a magnetic field and look for disortions that indicate gaps,basically. In can detect damage that's invisible to the eye.

If you're already taking it off and it's a 2000, you might think about just junking it and replacing it with a TUPY or clearwater head instead of bothering to clean and test. Same work to get your rig back together either way.
 
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