08 Mysterious milky oil... Help!

Hello, everyone. First time poster. I hope y'all can help me troubleshoot my problem.

Last winter, I had an issue with one of my springed lifters. It seized closed and was causing a misfire. I took the engine apart, and decided to have the heads cleaned and new seals installed. After I got them back and reinstalled everything, I had an issue with coolant leaking out of the back of the head. It would leak all the time, on or off. I finally found the issue coming from the coolant crossover "terminator block" on the back. It has a small O ring which I had missed. After installing the seal, I have driven the truck for over a year with no problems.

I was driving back from a 3 hour road trip when my check engine light came on. I noticed the oil pressure was low for highway driving, so I pulled over to check the oil level. I usually have to top it off before its time to change the oil (probably the baffle issue on the valve cover). I pulled my dip stick and it was covered in milky oil, top to bottom. I went ahead and put a quart of oil in it, since the timing was right for my usual top off. As much as I hated to, I was wearing a suit and it was cold, so I decided to drive it home and pray it didn't damage the engine.

I got a little ways down and my oil pressure flatlined, causing the "STOP ENGINE NOW" warning to come up. It wasn't knocking or doing anything suspicious. I pulled over and let it idle, then revved it some and it sounded fine. If I really didn't have oil pressure I would have known.

Short version, I got it home, and pulled the valve cover and intake manifold off. I replaced the oil sensor, which fixed that problem. The valve cover was 100% clean, no milky oil issue. The oil drained fine, no foam and no sign of moisture. I removed the dip stick tube and cleaned it out. I asked around, and since my coolant level wasn't going down, I decided to put it back together and chalk it up as some rouge moisture got in there.

Drove fine for two days, now I check my dip stick and its covered in milky oil again.

I'm confused, since it is not doing any of the usual signs of a bad head gasket, eg loss of power, smoking, rough idle, coolant loss, or overheating. The truck still runs perfectly fine.

This has me really concerned and stumped. If the oil is that milky on the stick, shouldn't it be caked in around the lifters and such? I only pulled one valve cover, is it possible to have a problem on one side without it making a mess on the other?

This is an 08 LTZ with 120k on it.

Thanks guys!

It probably isn't the cause of your milky oil but I can see where you are missing a bolt in your pic showing the oil filter interface.  Looking at that pic, if you go straight up (very slightly to the left of straight up) you can see a bolt head.  There should be another one on the right side of that piece that the visible bolt is going into.  May well be the source of the oil residue seen in the pic, outside of where the filter attaches.  From that pic it almost looks like that piece is broken where the other bolt is supposed to go in, but hard to tell from that pic.  That piece should be symmetrical with both sides the same.  Oil flow goes through that piece.

I suggest draining oil and examine it...

Are your drives short and it is cold out?maybe moisture never has time to burn off? or PCV is not working?

HOw is your coolant level?

I drained the oil the first time it did this, and it looked as pictured in the photos. Aside from the mess in the dip stick tube, I didn't see an residue anywhere else, and the oil was clean and free of coolant.
However, I checked my coolant today and it was about a cup lower than before. Seems I have a slow coolant leak somewhere.

I wrote that off, because if you look on the oil filter pic, the bolt on the top right has a little bit of coolant on it. I assumed I had a slight external leak, but it must be leaking both ways.

My drives are usually long, the moisture should be burning off.

It may be worth mentioning thsee problems didnt start until after I made a trip north over the holidays and it was -6 out. Even up there, most drives were 40 minutes or better.

Last thing, I had noticed gurgling in the heater core, but it has since stopped.

Is the oil milky or more like caramel?

If it is milky it could be due to air... If you put too much oil in it you can have milky oil. Not sure if you let it sit for a while if the air settles back out. Too much oil in your truck and the oil in the pan can come into contact with moving parts which cause it to blend air into it causing it to look milky.

If you have coolant in the oil it will get really thick (Atleast both times I have seen it that was the case) and will look more like caramel.

If you drain the oil out it should be obvious if it is milky due to air entrapment from too much oil in the pan or if due to coolant.

Rodney

Gurgle
Cup low

I would do a pressure test on cooling system to see if you have a leak.
Run it up to just above the cap pressure rating.

I will mention that on my truck I have no indication of a coolant leak into my oil other than loosing coolant. There have been no issues with runability or smoke. So don't assume that you will have one of those issues with a blown gasket or cracked head.

Rodney