Knock sensor questions

[L0G1C]

If your knock sensor is leaking, is there a way to fix it other than replacing it? I can't find it cheaper than $70 around here and I don't have the money to fix it right now unless it's cheap. I haven't ever seen one removed from the car, so I don't know what is actually leaking out of it or where it's coming from. Any info would be appreciated!

 

[psychlow]

Really, all most knock sensors are just a microphone. It just transfers sound within a certain KHz range (6-8KHz, specifically) to the ECU.

You could theoretically build your own and try that out, but it probably would be worth it to buy a new OEM unit. Taking chances on a sensor that critical is usually asking for trouble, unfortunately.

 

[cyrusdrum]

Doesn't a knock sensor use piezoelectric crystal? don't think you can build one. But if it is leaking couldn't you just un-screw it and put some RTV on the threads and put it back in. unless it is cracked, then you will need to buy a replacement.

 

[L0G1C]

What about the "goo" that's in it. I figure that it must dampen the noise that it picks up on so that it doesn't think noises like lifter tick is detonation. I was thinking about trying to refill it with something and put it back on and see what I get. The car runs great regardless of the knock, and I don't see any reason that it would be picking up on 43 counts of knock at any level of accelleration.

 

[psychlow]

I'm not sure which way it's set up on DSMs, honestly. Some use a tuned crystal to generate a pulse voltage, yes, but on the 1000FAQ on the VFAQ, it describes it as just a microphone, with the ECU deciphering the data and picking out knock.

Sure it's possible to make your own, even if they need a crystal (and maybe a couple semiconductors). Again, you're still playing with fire.....