I just finished putting in a set of headers on my 84 L69 and now I've found that I've broke a sensor. It's on the passenger side. The wire comes from the harness and reaches rearward. There is some metal tape on the wire so it must have been near the manifold. My fan switch is still intact so it's not that. What other sensor is attached to the pasenger side block? The part is black, it's cracked in half so the other part must still be installed. I can see what looks like a very very small metal rod in the middle.

 

The knock sensor.

 

broken parts go in the trash

 

Well, it was my coolant fan sensor. I was looking at a sensor/switch? that is farther down on the block, almost directly below the coolant fan sensor. Anybody know what that one would be? Also, when I got the replacement coolant fan switch, the brass tube that fits in the block is much larger than the one that came out. Probably by a 1/4" The threads are correct as is the connection, just a larger diameter brass tube. Will that cause any problems in the water jacket of the block?

 

Thats what the round sensor at the bottom of the block is.

 

The radiator fan switch goes in the head. The knock sensor goes in the block. Both go into the water jacket.