2007 4.3 Volvo Penta, what are these, and why is there 2 ( on each side of block )

[dizzyalpaca]

Hey guys,

I am replacing my 2007 cracked 4.3 penta block with a 2009 4.3 gm block

I noticed they have these sensors on each side of the block, that look they have drains plugs? What are they used for? And do I need to run both?

My GM block I have has a huge 1” x 27mm port on one side that was used for a block heater and a 1/4” port on the other side I can install one of these sensors.

My question is, can I just plug the 27mm port and only run this sensor on the one side?

 

[alldodge]

The piece on top is a knock sensor. If the motor starts to knock the ECM will retard the timing to protect it

 

[dizzyalpaca]

The piece on top is a knock sensor. If the motor starts to knock the ECM will retard the timing to protect it

Thanks! Yes, that’s what I figured out. Appreciate it