Yellow "gunk" on my oil cap???

[Old77]

What is this crap on the inside of my oil cap?? On our trip back from Indianapolis we stopped in Illinois for us all to pee and got back in and got an "Add oil" alert. I went to check and indeed I was a quart low. Don't know why but maybe the two are related. Went to fill it up, took off the cap and bamo! This is what it looks like. I added the oil, cleaned the cap and journeyed on to KC. Got to KC, filled up with gas, checked again and the gunk was back again!!! What the heck is this stuff??? I'm afraid for the worst...

 

[Old77]

Forgot to add but not sure if it matters...

This is on my 2007 Suburban
5.3 L motor
112k miles
Last oil change was last September (approximately 3500 miles ago)

 

[davbell22602]

Might be your t stat causing it or leaking head gasket or leaking intake gasket.

 

[skysurfer]

The only thing I've experienced close to that was when I rode a motorcycle across several states at 80-100 mph in 100+ temps. When I got to Colorado the oil had turned foamy white and looked like someone poured a latte in the crankcase. I guess that happens when oil completely breaks down.

In your case I would suspect the sulfer in your oil has separated (if that's possible) and should be changed, but that's just a guess.

 

[Old77]

Explain please What would my tstat have to do with yellow gunk appearing in my oil filler cap??? My temp is staying right around 200 - 210 like it always has. Never gets any higher than 210 or lower than 190ish...

 

[Old77]

The only thing I've experienced close to that was when I rode a motorcycle across several states at 80-100 mph in 100+ temps. When I got to Colorado the oil had turned foamy white and looked like someone poured a latte in the crankcase. I guess that happens when oil completely breaks down.

In your case I would suspect the sulfer in your oil has separated and should be changed, but that's just a guess.

Definitely worth a try. After today I was definitely planning on changing it after work tomorrow. I wonder what it'll look like coming out of the drain plug....

 

[Sasquatch]

That`s unfortunately a sign that there`s antifreeze leaking into the crankcase.

I`ve seen it many times and it always looks like light colored foamy chocolate milk under the cap and also on the dipstick.

 

[Old77]

Is that a head gasket issue or ?????

 

[Sasquatch]

It could be a head gasket or an intake gasket.

I just did a little research and a bunch of people say it`s normal to have yellow gunk under the cap due to short winter trips when the engine doesn`t get a chance to get hot enough to burn off any condensation. But i`ve never had it on anything i`ve ever owned.

But the fact that you cleaned it off and it came back in a short amount of time tells me that it may be bad news.

Just to be safe i wouldn`t drive it until you get a chance to drain the oil to see what it looks like.

Did you happen to notice if your antifreeze was low?

 

[Irishman999]

Never have seen or herd of yellow foam inside a crankcase.... does the burb use Dexcool?

 

[oneluckypops]

What kind of Oil are you using?

If it was coolant mixing with oil it would NOT look yellow, it would be a sludgy feeling and like someone else stated it would look like chocolate milk.

To me it really looks like you have used some kind of additive in the past.
I can not remember which oil's have this but there are some that have leak detection dye in them. And honestly thats what it looks like to me is a dye, Try looking at the cap with an ultraviolet light.

 

[CknightK10]

I wouldnt be extreamly worried. I do not believe it could be coolant due to the color like it has been mentioned. In my experience with oil mixing with coolant it comes out as dark grayish or brown. If I were you I would just change the oil and filter. If your engine does blow up, you always have the 77

 

[Irishman999]

I would not be surprised by anything with your burb, my father in law's got an 07 Tahoe that has been nothing but problems.

 

[Old77]

first off, thank you to everyone jumping in to help! I love this forum!

To answer a few questions that might help...
1. I use Penzoil 5w-30. Have not used any additives other than just the oil and I've used this same oil for quite a while now but that's not saying that the didn't change it this time around
2 with that said before we left I did put in some STP injector cleaner but I'd doubt putting that in the gas tank would show up in the oil.
3. We've had this burb since last July and this is the first long trip we've taken with it. All other use has just been around town. Literally about 400 miles a month. As stated, due to this I haven't changed the oil since last September. Could this contribute to it? As mentioned by Sky could the oil just be breaking down? I was a 1000 mile trip I've never seen this before though and we've made this trip quite a bit over the last 10 years....

 

[oneluckypops]

O77 I would recomend to NOT use Penzoil, personally I run Valvoline with wix filters.
Also I could see the stp mixing with the oil, it is ment to clean, which will clean the cylinder walls and cause the rings not to seal letting the STP leak past the rings and mixing with the oil, I would change the oil to Valvoline and not worry about it.
Sorry man I have replaced alot of Motors from the owners using penzoil I wish i still had the pictures of the filters from a 100000 mile motor with Penzoil and another that ran valvoline, It is nasty

first off, thank you to everyone jumping in to help! I love this forum!

To answer a few questions that might help...
1. I use Penzoil 5w-30. Have not used any additives other than just the oil and I've used this same oil for quite a while now but that's not saying that the didn't change it this time around
2 with that said before we left I did put in some STP injector cleaner but I'd doubt putting that in the gas tank would show up in the oil.
3. We've had this burb since last July and this is the first long trip we've taken with it. All other use has just been around town. Literally about 400 miles a month. As stated, due to this I haven't changed the oil since last September. Could this contribute to it? As mentioned by Sky could the oil just be breaking down? I was a 1000 mile trip I've never seen this before though and we've made this trip quite a bit over the last 10 years....