So I was doing cleaning under the hood and happened to look at my coolant reservoir and I took off the oil fill cap, and noticed a thick orange sludge on the inside of the coolant reservoir and a thick yellow goop inside the filler cap. Now, I've worked on my cars in the past, but have never noticed this. This normal?

 

Trying to add photos, but system wont seem to upload.

 

Has it been cold where you live? Lots of short trips?

That's condensation buildup. You need get your truck up to temp and take a long drive.

 

first, what year is your truck and what type of coolant do you have? the gold and orange coolants are organic based and some build up is normal, but it also might be time to change coolant. a simple ph strip test will tell you ph, alkaline and strength

 

Scratch my reply. I read your post wrong. When you said oil fill cap I thought you were talking about the actual oil fill. You meant the resivoir cap.

I apparently was a little more tired than usual this morning

 

2010 Lariat
Orange Coolant. Not sure of the type since I just bought it and it was what was in the reservoir.

 

Yes, its in the cap where you fill oil.

 

head gasket leak?

 

First you say oil fill cap, then you say coolant, then back to oil...

If it is the oil cap, the first answer is correct.

 

Just flush it.