Believe I have found the source of a coolant leak to be the passenger side knock sensor.
Is this somewhat common?
Is it usually just the threads need to be cleaned and pipe sealant applied, then re-installed OR do I need to replace it?

If I need to replace it, what brands should I stay away from? Of course the Delco part is twice the price of other brands.

If I replace one, I might as well replace both sides...since I have to drain the block....oh what a mess this is going to be!!!!


Thanks

 

Is this on your 96 Silver Vette? How long have you owned this vehicle? Do you do your own service? Have you properly serviced the cooling system in the last ?? years? Has the cooling system EVER been serviced to your knowledge?

Here's why I ask:

A proper coolant change includes draining the block, which involves removing the knock sensors. I tend to think you wouldn't be asking these questions if you had messed with the knock sensors to change coolant in the past 5 years.

To answer your questions though, In my experience knock sensors that go to leaking on their own are not common. The end of the sensor that goes into the block is essentially a pipe plug. Before a sensor rusts out enough to leak, all your freeze plugs would have rusted out and leaked long ago.

On the other hand, if the coolant has been change recently, to include flushing the block by removing the knock sensors, then it is entirely possible that the sensor wasn't torqued adequately. It doesn't take a lot of torque - seems like I recall a number like 14 or 18 ft-lbs.

So, you either need to change the coolant anyway, or if that has been done recently you might want to catch all the coolant, filter it and reuse it. Lowes or Home Depot both sell black plastic tubs for mixing a bag of ReadyMix cement. They cost less than $10 and are great for catching all manner of fluids, especially coolant and ATF, or any other fluid that finds a drain path that bypasses the spot where you set the drain bucket. Also, they are short enough to slide up under a car on ramps. A mechanic's creeper will keep you up off the ground and pretty much bone dry throughout the process.

There's no real reason to change both sensors if the left one is sealing properly and shows no signs of rusting or leaking.

If you were talking about your wife's Prius, I have no idea what the problem might be.

 

As long as you are not having any problems, the knock sensor can be removed, the threads cleaned (both the sensor and the block) and re-installed. I would suggest using anti-seize compound and tighten to spec.

One thing that removing then will do is to let you do a good coolant system flush and refill. Because the sensors sit at the bottom of the block coolant passages, there will most likely be some junk that doesn't get cleaned out with just a drain and refill. It may be that there is enough material in there that coolant may not easily drain out. You can use a piece of coat hanger wire to loosen any blockage.

 

 

Yep, this in on my '96 CE LT4; have had this car long enough that I should have done a complete flush and have not. I have replaced the radiator though and did put fresh in then...but I know that is not a complete flush.

Leak appears to be coming around the threads. Not constant, some days it leaks, some days it doesn't.

Sooooo....time for me to get busy and flush the cooling system. I will get a larger catch pan than the ones I have...as coolant always seems to finds a path that is just beyond the ones I have used in the past.

But just in case I break a sensor somehow, what brands are okay to use besides Delco?

Thanks for the replies.