So while replacing the coolant temp sensor and coolant temp gauge sensor, I discovered what looked like orange paint on their tips. Looking inside the thermostat housing, this is what I see.

Any idea what this could be? Rust? Paint? It can't be normal. A quick google search didn't find anything similar. I'm about to take off the top of the thermostat housing to look inside.

 

Okay, not as bad as I thought. It was only a bit concentrated around the coolant temp gauge sensor. Still not sure what it is but I was worried I'd have to run out for a new thermostat and housing to be safe.

Full disclosure: a few years ago I had a bad coolant leak and filled the radiator with regular water to get home. Wondering if this could be buildup from that. Also had the valve cover painted ("powdercoated" by a shady shop) orange but that seems like a stretch.

 

cant see any images

use something like www.imgur.com to host your images

 

Yeah your images are broken.

 

Mineral build up.

 

Radiator flush may be in order to clean all that out.

 

Fixed pics

 

It sort of looks like the residue from the thread sealant stuff that's on the original oem sensor.