Technical What is this bolt?

[jakubjlew]

Complete novice. I turned the car on today and let it run for a few minutes. I saw maybe 3 drops of oil on the floor and I tried searching for a source. While I was looking I found what looks like a bolt with a hole in the middle. It also looked like there was oil in the center of it, like maybe some had dripped out of there. Can someone tell me what this is, and more importantly, if it makes sense that there could be oil dripping out of it?

 

[bugsymike]

Others will be able to give more accurate detail, but I suspect it is a indicator for head gasket seepage via a milled grove around the head/cylinder block area.

 

[dirkdeman]

Mike is correct! These engines are fitted with a hollow bolt. This is a safety measure to prevent noxious exhaust gases to enter the cabin, should the head gasket fail. (The cooling air is also used for heating, as opposed to cars with a separate heater).

If there is oil dripping out of the bolt that would mean you have oil on top of the piston, likely meaning worn piston rings or grooves in your cylinder wall, as well as a failing head gasket. You can easily check it by feeling and listening, as there would be distinct sound coming from the hollow bolt and you'd be able to feel it too. It would also mean you're burning oil so check for abnormal smoke from the exhaust.

 

[jakubjlew]

Thank you both! I didn’t hear anything coming from it, but like I said, there was oil on my finger after touching the bolt.