Knock sensor replacement -- thread coating?
Thread Starter
Burning Brakes
Joined: Aug 2010
Posts: 951
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From: Placerville CA
Knock sensor replacement -- thread coating?
I'm about to replace the two knock sensors removed for a cooling system flush and radiator replacement on my '94. (Geez, there was something like MUD in there! And I'm still soaking the surge tank to get out the residual. If anybody has any tips on something that dissolves that old anti-freeze sediment let me know.)
But my main question is, what do you guys use on the knock sensors when replacing them -- the old ones, I mean, not new ones: teflon tape? pipe dope? thread lock?
The old ones had a red substance on the threads, and from the way they came off I'm inclined to think it was some kind of thread lock stuff.
But my main question is, what do you guys use on the knock sensors when replacing them -- the old ones, I mean, not new ones: teflon tape? pipe dope? thread lock?
The old ones had a red substance on the threads, and from the way they came off I'm inclined to think it was some kind of thread lock stuff.
Race Director
Joined: Nov 2003
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From: Overland Park Kansas
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I used teflon paste for sealer.
I used Purple Power degreaser to remove sediment in the overflow tank.
Seems like I remember reading that mud can be an indication of oil seeping past your headgaskets into the antifreeze.
I used Purple Power degreaser to remove sediment in the overflow tank.
Seems like I remember reading that mud can be an indication of oil seeping past your headgaskets into the antifreeze.
Thread Starter
Burning Brakes
Joined: Aug 2010
Posts: 951
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From: Placerville CA
Seems like I remember reading that mud can be an indication of oil seeping past your headgaskets into the antifreeze.
Thanks for the cleaning tip. I suppose if degreaser works almost any detergent should do the trick. That surge tank has a plastic backflow valve, I think, so I don't want to use anything too harsh.
Race Director
Joined: Jun 2004
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From: WI
I believe that's a one wire sensor and needs to get grounded to the block so the red material on the threads is probably anti-galling compound. Use a compound that isn't going to coat the threads so much. Try just anti-seize. Medium or low strength thread lock may work well too. If you have to use thread sealant to stop it from leaking, apply the sealant on the last threads that are in the block. Not all the threads or the first threads. Make sure to clean any sludge off the sensor!
Do not over torque the sensor!!! The torque valve is specific to set how sensitive the sensor is.
Cleaning a reservoir is pretty easy. Put some shot gun shot in there and shake it! Or marbles etc etc. The material coating you are seeing may be anti-corrosion compounds in the coolant!
Do not over torque the sensor!!! The torque valve is specific to set how sensitive the sensor is.
Cleaning a reservoir is pretty easy. Put some shot gun shot in there and shake it! Or marbles etc etc. The material coating you are seeing may be anti-corrosion compounds in the coolant!
Team Owner
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From: Fort Knox, KY
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The orange coating that comes on the new replacement sensor is all you need. If you add liquid teflon or plumber's tape, you risk negatively effecting the sensor's ability to detect (and most importantly) retard spark knock.
Last edited by onedef92; Sep 8, 2010 at 11:03 AM.
Le Mans Master
Joined: Jul 2007
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From: Tampa Florida
with all the above.The sensor's threaded portion is made of brass so you really don't need much if any "sealing" compound on that since the thing will conform with a little tension on the threads.
The threads of the sensor do ground the sensor so if you apply teflon tape you run the possibility of insulating the grounding portion of the circuit which will throw a code as mentioned above.
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Drifting
Joined: Jun 2010
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From: Westerly RI
I agree, for new sensors. I believe the OP was asking about used ones, after draining the block.
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I would try it without any sealing compound first, then if a leak does occur, go the sealing compound route (applied very sparingly). Be sure and torque the sensor in to FSM specs.
