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Problem Removing Knock Sensor - Help Please


Ol'Jim
11-18-2017, 12:21 PM
Oh, boy. Got a real problem here. Trying to remove/replace a faulty aftermarket Knock Sensor. It is only 4 years old, AutoZone Duralast house brand.
I am turning the 22MM socket, but it seems the crimped-on top piece of the sensor (with the hex on it) is just turning in the lower body of the unit. It is not coming loose. (ANOTHER reason to use ONLY GM parts for this job!).
The KS sits in a well that is a few inches deep, and there is almost NO room around the outside of the KS body, very little clearance, I can't think of any tool I can use on the OD of the body to try and turn it. This thing was only torqued to 10 foot-pounds, and there is no sign of corrosion in the well, so I would think it would come out fairly easily..
Anyone got any ideas on how I can get this thing out? I suppose I could try tapping on a chisel, on the upper/outer edge? Or, if I were to somehow destroy the sensor by ripping thew top part of it off, is there anything inside it that I might be able to dig into and turn it with a large screwdriver?
Any suggestions will be appreciated! Thanks in advance, -Jim.

https://farm5.staticflickr.com/4533/38449655466_fbdf783218_n.jpg (https://flic.kr/p/21zEx1f)Knock Sensor in engine (https://flic.kr/p/21zEx1f) by ChevelleSS454 (https://www.flickr.com/photos/76128419@N02/), on Flickr

Ol'Jim
11-18-2017, 02:00 PM
Think I am going to try drilling a pair of holes straight down through the top and body of the KS, and run some screws down through to lock the 2 pieces together, and try using the socket again to turn the unit.
I have no idea what the inside of these things looks like, but unless anyone has another idea, I don't know what else to try.

Ol'Jim
11-18-2017, 03:44 PM
That did the trick. 9/64" drill straight down at the outer edge of the top, where it meets the crimp. Then ran a 1" long #10 machine screw down into the hole. the panhead was fairly tight to the 22mm hex on the sensor, so if you ever have to do this, make sure to drill out along the edge, where a flat of the hex is, to give you some room for the screw head. Tightened it down as far as it would go to allow the 22mm socket to go over the hex.
https://farm5.staticflickr.com/4521/38451487636_22bf38c8ff_n.jpg (https://flic.kr/p/21zPVDo)Old KS (https://flic.kr/p/21zPVDo) by ChevelleSS454 (https://www.flickr.com/photos/76128419@N02/), on Flickr

Ol'Jim
11-19-2017, 10:05 AM
RockAuto.com - GM/AC-Delco Knock Sensors $41 each. Postage for 2 was like $3. Delivered in 2-3 days. AutoZone, O'Reilly and everyone else sells chinese junk units for $55-65 each.
Their lifetime warranty don't help much when you gotta do a 3-4 hour job all over again.
My original GM units - One failed at over 200,000 miles, the other still good at 278,000. Changed the defective A-zone part that lasted less than 40K miles, (and the other factory one, just because). Also - ALWAYS replace the pigtail/harness while you are in there! These sensors work at very small milli-volt signal levels, so don't chance it using a corroded old harness. Plan ahead and get your parts before you start the job. Most stores don't stock the harness.

j cAT
11-20-2017, 08:32 AM
it would be good to show the removal of this sensor that refused to unscrew.
so after you removed the sensor was the sensor metal reacting with the intake manifold ?

many had problems with after market KS on these . it is very important that the sensor output is with in the GM spec.. this if too high or low can cause issues not just a CEL...

Ol'Jim
11-21-2017, 12:45 PM
it would be good to show the removal of this sensor that refused to unscrew.
so after you removed the sensor was the sensor metal reacting with the intake manifold ?

J Cat, I did post a picture of the bad one, after I removed it. In the last picture I added, you can see the screw head on the top of the sensor body. You can also see the threads of the stud, and there was no visible corrosion. But there was a dark substance between the threads, and the tapped hole had some in it's threads. Maybe it was some type of corrosion, I thought perhaps it was from the poor plating that they coated that Autozone unit with.

j cAT
11-21-2017, 06:38 PM
I saw the picture link now .. that KS crimp on some after market KS is a problem... the OEM are much stronger.. on my 96 Impala I remove the 2 KS on the block drain ports every 4yrs but I do use Teflon paste of a very small amount because many have had removal issues since these are exposed to the rust belt road salts..

Teflon paste amount is very small coating like paint ... keeps threads from damage .. I also put a small dab of dielectric grease in the connector boot..

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