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NAM75

No threads left on knock sensor

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NAM75

I have a 1999 response

 Pull the plugs to winterize it and drain the water and the engine block threads for the knock sensor are gone.

 It won’t go back in.

 I guess I can dry winterize it and get all the water out this year. I normally use Anti-freeze.

Any suggestions on a repair for the spring?

Can I tap it and put in new threads? 

Thanks crew!

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oldjeep

You sure they are actually gone?  Take a little wire brush and make sure they are not full of crud.  Would be pretty crazy if the block threads gave up before the threads on the tin knock sensor.

Fix might require drill, tap and a really solid adapter.  Knock sensor isn't likely to like a helicoil.

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MadMan
20 minutes ago, NAM75 said:

Can I tap it and put in new threads? 

I recently did this on a friends boat.  It worked.

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NAM75

This is actually the 2nd knock sensor.... 1st one rusted out

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dlb

Dry winterizing is actually what the Manuel recommends.

Try cleaning out the crud from the threads as highlighted above before you put it up for the winter.

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Nitrousbird

Chase the threads.

Threads on my V-drive drains gave up the ghost.  I chased the threads and good to go.

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NAM75
On 10/5/2018 at 8:12 PM, Nitrousbird said:

Chase the threads.

Threads on my V-drive drains gave up the ghost.  I chased the threads and good to go.

What size chaser did you use...  I think it’s a 1/4” 18 ntp?

 

Thanks!

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BVO

I have an 07 VTX and went to winterize it this year.  When I went to remove the drain plug and knock sensor from the drivers side (starboard) I found it came out with just a quarter turn.  I had someone else winterize last year and they apparently cross threaded it when they put it in.  I tried to get a tap (14 x 1.5) and re thread it but it cut a new thread path and now the bolt will not turn all the way down without hitting the side of the block.  It will not tighten enough to hold water in the block.  Looks like I need to drill, retap with a larger size and us a helicoil or equivalent.  Has anyone had experience with this?  Will a right angle adaptor work with a regular drill to drill the hole.  I don't have a right angle drill and hate to but one just for this.  I am nervous about getting the wrong angle when I redrill  and have the same issue again.  Any suggestions?

Thanks for any assistance. 

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oldjeep

That sucks.  The driver side is the one with the worst clearance around it.  No good ideas for doing it easily with engine in boat, but they do sell cheap, light duty right angle adapters you could use on a cordless drill.  I'd use a brass adapter rather than a helicoil in that location. 

Edited by oldjeep

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BVO

Yes, the drivers side has more obstacles.  Not encouraging when you say "No good ideas for doing it easily  with engine in boat".  I was hoping for something more like, "Yea, no big deal".  I guess I will order a right angle adaptor and threading kit with brass and see what I can do.  I will post my results but not in a huge hurry given the time of year.

Side question, would it be good to cover the existing hole to reduce any corrosion inside the block?  A pice of tape or something.

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oldjeep
1 hour ago, BVO said:

Yes, the drivers side has more obstacles.  Not encouraging when you say "No good ideas for doing it easily  with engine in boat".  I was hoping for something more like, "Yea, no big deal".  I guess I will order a right angle adaptor and threading kit with brass and see what I can do.  I will post my results but not in a huge hurry given the time of year.

Side question, would it be good to cover the existing hole to reduce any corrosion inside the block?  A pice of tape or something.

Not sure if it matters, but it won't hurt anything to tape it.  The biggest issue with leaving the block plug out is that the threads rust up which isnt really a problem anymore.   

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jmack

I had the same issue with mine and I repaired them with helicoil inserts. You'll have to drill and tap to repair it with a brass adapter. I was able to get a tap started in the existing hole without drilling for a helicoil. I likely would have had to pull the motor to get to it with a drill - even a right angle drill. I used JB Weld on the helicoil inserts to lock them in place - no issues with the knock sensors. And helicoils are stainless, so no more rust issues.

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BVO

Any idea if I could plug the existing hole with JB weld and drill another hole where ever I can get the drill lined up?  I would think that as long as I am in the lower part of the block, I shouldn't be in danger of drilling into something and causing additional damage. 

I guess I will call the dealer in the morning and see what they say about doing this work.  I don't have equipment to pull an engine out of a boat.

Any ideas are appreciated!

Thanks guys.

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oldjeep
On ‎12‎/‎9‎/‎2018 at 10:53 PM, BVO said:

Any idea if I could plug the existing hole with JB weld and drill another hole where ever I can get the drill lined up?  I would think that as long as I am in the lower part of the block, I shouldn't be in danger of drilling into something and causing additional damage. 

I guess I will call the dealer in the morning and see what they say about doing this work.  I don't have equipment to pull an engine out of a boat.

Any ideas are appreciated!

Thanks guys.

Which type of knock sensor have you got?  If it is the single wire style you can't use JB weld as it grounds through the block.

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Bozboat
17 minutes ago, oldjeep said:

Which type of knock sensor have you got?  If it is the single wire style you can't use JB weld as it grounds through the block.

I think OP was asking if he could plug the original hole with JB weld and drill a new hole nearby?  If so, this sounds like a bad plan.

 

Get a tap and die set and just recut the threads on the existing hole?

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oldjeep
6 minutes ago, Bozboat said:

I think OP was asking if he could plug the original hole with JB weld and drill a new hole nearby?  If so, this sounds like a bad plan.

 

Get a tap and die set and just recut the threads on the existing hole?

Ah, that would be a bad idea.  I was thinking that he wanted to plug it and then drill the JB weld

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jmack

I agree - try chasing the threads, but in my case, there wasn't enough material left. And no, I would not plug the hole with JB weld or try drilling in another area. There is a boss cast in the block where the sensors / plugs are located so that there is enough material to drill and tap. Other areas of the water jacket will likely be too thin.

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MadMan

You could try to cut new threads with a tap the is the next size up pipe thread without drilling at all.  Then use a reducer the get it back to the right size, or just plug that side and install the knock sensor on the other side of the block by extending the wire.

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justgary
On 10/7/2018 at 4:36 PM, NAM75 said:

What size chaser did you use...  I think it’s a 1/4” 18 ntp?

 

Thanks!

OP, did you get this fixed? 

Pipe threads are tapered, so I'm surprised that you can't get the sensor to thread on.  Does the block have any threads left at all? 

I'd be inclined to make a custom brass fitting for the block and put the sensor in it, and just leave the block alone once I had the fitting in. 

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jmack
3 hours ago, MadMan said:

You could try to cut new threads with a tap the is the next size up pipe thread without drilling at all.  Then use a reducer the get it back to the right size, or just plug that side and install the knock sensor on the other side of the block by extending the wire.

The hole won't be big enough to get a tap started to use a reducer (it's currently 1/4 NPT and he would have to go up to 3/8 to use a reducer). I know because I had the same issue and looked at different solutions. I was able to get a tap started for a Helicoil thread insert without drilling, and that fixed my issue. My threads were rusted out on both sides of the block. I suggest trying to use a 1/4 NPT tap to clean up what's left of the threads, but if that won't work, just go with a thread repair kit.

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justgary

OP hasn't posted to this thread for two months now.

I'll add that while I really like the thread insert idea (especially if it is stainless), but it just occurred to me that on a Response it should be pretty easy to get to the problem. 

As a rambling thought, I would also consider cleaning the hole really well and using a torch to braze a little brass in the hole and then rethread that.  That would give a very long-term solution also, but I do wonder what the heat would do.  Preheating the area a little would prevent cracking, but is it possible to warp the block?  Just a thought.

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NAM75

Haven’t been on lately.

I drained all the water out and get the knock sensor to hold in barely.... and got antifreeze in for the winter.

Ill fix in the spring and report back.

Thanks Crew!

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Chia
On 1/1/2019 at 4:59 PM, NAM75 said:

Haven’t been on lately.

I drained all the water out and get the knock sensor to hold in barely.... and got antifreeze in for the winter.

Ill fix in the spring and report back.

Thanks Crew!

That was the way mine was. Chasing the threads and installing a new knock sensor was all it took to fix.

Just needed chasing the old threads combined with the newness of the new threads on the new knock sensor. 

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