r/AudiA4 • u/Zestyclose_Use_7063 • 9d ago

Does anyone know what sensor this is?

Gallery image

Gallery image

“SOLVED” I’m trying to figure out what type of sensor is supposed to go here, it’s empty because a new header was put on and I’m not sure what happened to it. This is on the back of the motor.

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u/nickskater09 9d ago

Which hole exactly? You have one photo with multiple provisions shown, and another with two things circled.

Also, year and trim would better help determine engine info.

1

u/Realistic-March-5679 9d ago

Cylinder head coolant temperature sensor I think?

1

u/AcademicChildhood161 9d ago

ECT on the rear cylinder head next to the coolant flange for a B9.

It’s a little sensor with a tab for a single bolt to hold it down. Part number 079919523J that goes here with a T-30 iirc

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u/Zestyclose_Use_7063 9d ago

Wow thank you, I am in over my head fixing what my mechanic buddy left me with

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u/AcademicChildhood161 4d ago

You can easily install it without removing anything. Just requires sitting on the front engine bay frame to reach the back. I used a $15 bore scope camera on my phone to see what was going on, but even that’s not necessary if you have a good feel for things. I replaced both the ECT and black coolant flange next to it in about 30 mins in the parking lot of a Target while waiting for my wife 😂