Could an air leak into the valve cover produce creamy brown oil?

Question

I've read multiple threads on diagnosing the creamy-colored-oil issues, but I don't feel like those answers fully pertain to my problem. Most threads indicated that one day the car started acting funny, they checked their oil and - lo and behold - they saw coffee. I too saw this and took steps that I thought would fix the problem, but my first test drive after "fixing" it, I pulled over after not even 2 minutes of driving to discover coffee on my dipstick again! 2 MINUTES!

I have a 2004 Jeep Cherokee 4.0, and upon discovering this contamination of my oil the first time I did the following:

1. Drained all of my oil.
2. Took off and cleaned all components from the cylinder head up.
3. Installed new head gasket (although I couldn't see any blown or heavily worn areas)
4. Reused the valve cover gasket but applied copper gasket sealer.
5. Inspected my oil pan after refilling my cooling system to the top ( to check for any water )
6. Replaced oil filter and added new oil.
7. Took it for a spin.

Like I said, not even a two minute drive and I discover creamy colored oil yet again. No performance issues, just cream. So it leads me to think that a water passage might have somehow leaked into an oil galley (is that possible?) in the block or head...also I noticed my valve cover wasn't properly tightened (I could hear a whistling noise while driving) and I tightened it promptly.

Could an air leak into the valve cover produce oil in that color?

Answer 1

The answer to your question is "yes" and "no".

There is a clue in your question you should address before you go farther. You stated there was a whistle sound from the valve cover. This is an indication the Positive Crankcase Ventilation (PCV) may not working properly.

The PCV system helps remove moisture, a major contaminant, from the oil.

A blocked PCV system will allow pressure buildup in the block and won't remove moisture. Over time, the increased moisture levels contaminate the oil, causing the creamy brown consistency.

This could be caused by the PCV valve itself, a collapsed hose or other blockage. PVC valves are typically inexpensive, so replace it. Check the rest of the components for issues. The below linked article has details how to do that.

A failed PCV valve may also cause noise. Some will produce a whistle or whine and others can produce a low moaning noise. The easiest way to verify the problem is to temporarily block the vacuum source to the PCV valve and see if the noise changes or goes away.

The most likely reason you saw the creamy brown consistency right away is because it builds up over time throughout the engine, a single oil change may not remove all the "creamy brown" residue. Once you have determined the cause, you may want to consider an engine flush to clean the oil passages.

Source - What are the Symptoms of a Bad PCV Valve

Answer 2

If you are getting water in the oil it will be from one of these events. One would be a natural occurrence of condensation forming in the crankcase and or valve cover causing the two to mix to the point a light brown, maybe like a dark chocolate, milk, but that would take the right conditions and a long period of accumulation for there to be enough to cause this event. A second scenario could be that the water is entering the oil from a compromised gasket between the cylinder block and the head. This will tend to have a coloration more of a tan color, or like you described as a coffee with creamer color. The third possibility would be a catastrophic failure (crack) of one or more cylinder block water cooling jackets and\or the water coolant jackets of the cylinder head itself. While I have been correct in calling for a head gasket on more occasions than not, I always do a pressure check on the engine coolant system before and after repairs. I have had them in my shop and never show a sign of a problem other than maybe a check engine light being on. I have also had them in my shop running so poorly that you could believe the pistons were actually swapping holes and even worse, I've had them come in on a tow truck so severely damaged that an engine replacement was the only option. So before I make that call I do these things.

1. I fill and inspect the cooling system visually and check for any coolant leaks externally onto the engine or leaking to the ground.

2. I visually inspect the grille and radiator for obstructions that could impede air flow across the radiator and engine.

3. Before starting the vehicle and while it is cool to the touch and not spinning of course, I check the serpentine belt(s) or v-belts to make sure they are there for one and are in working condition (ie. no cracks or big chunks missing from the belt) and also to ensure the belt(s) are not saturated with oil(another 4.0L problem for another time\discussion) If they are bad go ahead and replace them. I will then reach in and grab the fan blade and give it a forward, backward wiggle to see if there is any movement. If so could be time to change the cooling fan clutch. If it is not an engine mounted fan then I will feel for both the radiator and AC condenser fan assemblies and give each of them a wiggle. There will of course be movement in the direction which the blades normally travel, But there shouldn't be any movement laterally to the motor, or front to back movement if you will. If so, then it's time to replace the defective fan motor or fan assembly which ever you should choose.

4. Then, with all of that done and out of the way, I put my coolant pressure tester on the radiator opening and pump it to the equivalent of the normal operating pressure, which is (SAE Range 16-20 psi) or oe suggestion of 18 psi. At this point I go back and do step one again to see if any, external leaks have developed under pressure. If so, then note the item(s) leaking and replace them as needed. If there are no external leaks go back to your pressure tester and check the gauge. Has it lost pressure? If so pump it up again and check around on the ground to see if anything is leaking to the ground. If no visible leaks are present, then checking your pressure tester again. Has the pressure dropped? If so, pump it back up and open the passenger front door of the vehicle. Now peel back the floor mat and where the dash meets the floor board press your hand against the carpet and/or padding. If it is wet with antifreeze then it's time to replace the heater core.

5. If at this point there are no visable leaks in the coolant system, then you can proceed with a chemical block test of the coolant system to look for hydrocarbons in the coolant system. These kits are easy to use and readily available at most reputable parts suppliers.

[ After performing and failing the chemical combustion leak test you will be almost certain that you have properly diagnosed your problem as either a cylinder head gasket, a cracked cylinder head and or a damaged engine block. Luckily we have more steps..

6. With the combustion leak test failed you know you have an internal failure without a doubt. Next is to start your tear down and remove the cylinder head. Once the Head is removed you "can" visually inspect for leaks in the head and the block. However there is a valid reason to send your parts out to be tested at a machine shop. There can be fine hairline cracks that just are not visible to the naked eye. Unless you have them fluxed or magna fluxed then you are just taking the chance of doing the job all over again.

Sadly, that concludes the "Proper Diagnostic" for a possible head gasket leak. Just remember that most cylinder head leaks are just a symptom of an earlier problem. Either the engine is just old and worn out, or it became overheated at some point and compromised the gasket or worse cracked the head or block. But fixing the head, the head gasket or the engine block without finding the reason for the original failure will cost you dearly. As YOU WILL be doing the job again. IF I've missed any key steps in this diagnostic procedure, please feel free to add them or comment and I will correct them and give appropriate credit to who contributed.

Answer 3

I think CharlieRB nailed it about the PCV valve, but I wouldn't expect 2 minutes of operation to cream your oil.

If it isn't any of the other answers, or a D'oh moment installing the headgasket, I would look into the Oil Cooler (various part sites seem to suggest the 4.0 cherokee has one, if not you can ignore this). It is one of the only other areas that you haven't really gotten too where Oil and Coolant could potentially be mixing.

Also I'd like to bring more attention to the previously stated "1 oil change might not have gotten all the coffee out." It would be a shame to take it all apart again if what you are seeing is just leftovers.