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Fman

Knock sensor plugs

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Fman

I drained my block the other day removing the knock sensor plugs and wanted to find out if anyone wraps them with teflon tape when re-installing or just screw them back in with nothing. They were also pretty loose, I did not want to over tighten them, but wanted to find out if there was a torque spec on them? When I removed them they had nothing wrapped on them, so I figured it probably was not necessary to apply anything after drainging the block and re-installing.

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dlb

I do not do anything other than put it back in and tighten it. No clue what the torque I apply is.

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Pistol Pete

They're NPT so, you don't need any type of sealant/thread tape to prevent leakage.

This winterization season I did chase the threads in the block with a tap to clear some rust. That got me about 1.5 more turns of re-installing the KS back into the block.

Whatever you guys do, don't leave the Knock sensors or drain plugs out of the cast iron block for long. Rust will form quickly and make it almost impossible to get them back in.

As far as torque, real snug and no more. They don't need to be uber tight.

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Fman

They're NPT so, you don't need any type of sealant/thread tape to prevent leakage.

This winterization season I did chase the threads in the block with a tap to clear some rust. That got me about 1.5 more turns of re-installing the KS back into the block.

Whatever you guys do, don't leave the Knock sensors or drain plugs out of the cast iron block for long. Rust will form quickly and make it almost impossible to get them back in.

As far as torque, real snug and no more. They don't need to be uber tight.

Thanks Pete, I figured this was the case, thanks for the clarification.

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tvano

iirc you DO NOT want to use teflon tape on the knock sensors. that threaded portion of the sensor is part of the electrical circuit.

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Oberon

They're NPT so, you don't need any type of sealant/thread tape to prevent leakage.

This winterization season I did chase the threads in the block with a tap to clear some rust. That got me about 1.5 more turns of re-installing the KS back into the block.

Whatever you guys do, don't leave the Knock sensors or drain plugs out of the cast iron block for long. Rust will form quickly and make it almost impossible to get them back in.

As far as torque, real snug and no more. They don't need to be uber tight.

Do you recall what thread it was? My Dad's tap set didn't have the correct thread; is is a plumping thread?

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Indyxc

They're NPT so, you don't need any type of sealant/thread tape to prevent leakage.

This winterization season I did chase the threads in the block with a tap to clear some rust. That got me about 1.5 more turns of re-installing the KS back into the block.

Whatever you guys do, don't leave the Knock sensors or drain plugs out of the cast iron block for long. Rust will form quickly and make it almost impossible to get them back in.

As far as torque, real snug and no more. They don't need to be uber tight.

I half agree that if you leave them out the holes will rust. You can chase the threads in the spring, and they go back in just fine. That is what I do.

As for the size of the thread, it is a NPT, not sure which, I believe it is the smallest in this set:

http://www.harborfreight.com/6-piece-pipe-tap-die-set-91395.html

Edited by Indyxc

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Oberon

Thanks. I actually bought the SAE and metric sets. Figures it's a pipe thread.

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Steve B.

They're NPT so, you don't need any type of sealant/thread tape to prevent leakage.

This winterization season I did chase the threads in the block with a tap to clear some rust. That got me about 1.5 more turns of re-installing the KS back into the block.

Whatever you guys do, don't leave the Knock sensors or drain plugs out of the cast iron block for long. Rust will form quickly and make it almost impossible to get them back in.

As far as torque, real snug and no more. They don't need to be uber tight.

Uh-oh. I did just that of course. Thought I would leave them out for expansion, just in case kinda thing. Looks like I'll have to visit the boat in a month or so.

Thanks Pete,

Steve B,

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electricjohn

They're NPT so, you don't need any type of sealant/thread tape to prevent leakage.

This winterization season I did chase the threads in the block with a tap to clear some rust. That got me about 1.5 more turns of re-installing the KS back into the block.

Whatever you guys do, don't leave the Knock sensors or drain plugs out of the cast iron block for long. Rust will form quickly and make it almost impossible to get them back in.

As far as torque, real snug and no more. They don't need to be uber tight.

Pete, were you able to use a starting tap, or did you need a bottom tap.

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Indyxc

Uh-oh. I did just that of course. Thought I would leave them out for expansion, just in case kinda thing. Looks like I'll have to visit the boat in a month or so.

Thanks Pete,

Steve B,

You'll be able to chase the threads with a tap!

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dlb

I have left mine out every winter and never had an issue getting it back in in the spring.

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Pistol Pete

Pete, were you able to use a starting tap, or did you need a bottom tap.

A starting tap. I only needed to clear out a little bit of rust.

I have left mine out every winter and never had an issue getting it back in in the spring.

That's interesting.

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electricjohn

I have left mine out every winter and never had an issue getting it back in in the spring.

Same here till this past spring. We had a very snowy winter and a very wet spring. Had slight trouble getting both started back in this year. The rust was very apparent, and the threads (1/4" NPT course) were boogered up.

Edited by electricjohn

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martinarcher

You can get NPT bottoming taps here for a good price.

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Brad B

Its 1/2" x 18 NPT thread - I had to do mine this season.

Also I replaced the sensor this year - not sure if the old one was bad or not but it had some corrosion on the threaded tip.

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99response

Pete, were you able to use a starting tap, or did you need a bottom tap.

Starting tap worked fine for me, I've even fixed a cross threaded plug with one (I was not the one who cross threaded it BTW). IIRC its a 1/4-28 NPT tap, but bringing the knock sensor to the store will ensure you get the right one.

I have left mine out every winter and never had an issue getting it back in in the spring.

Ditto, times a few hundred boats.

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