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Spark plug thread Helicoil damaged

tc1234c

tc1234c

Well Known Member
Last Saturday after compression test it was hard to get the spark plug in #1 cylinder. After a few tries I noticed a corner of the thread came off. After pulling it out a little I noticed it is an insert. Only after I came home and read about it I learned it is a special Helicoil insert. I must distorted the first few threads. What worse is that this insert has serrated edge and requires special tool to install. Our local FBO does not have the tool. I checked with Hangar Tool Box (tool rental) and they don't carry this special tool. The installation tool and the tap set cost $1,200! Now I may have to take the cylinder off and ship it to an engine shop to get it fixed :(. Of course the coil costs only $8 and it is quick with the special tool. The advise I received from the mechanic is not to use too much antiseize and clean the thread often. This way will prevent the problem happening again.

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Yuk!

My flying buddy had the same problem on his H2AD. The solution was to use a small jeweler's file (if I recall correctly) and cut off the offending hang-nail. Seems to have worked as I flew his plane Saturday and all was well. Maybe Scott will chime in here.
 
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zilik said:
The solution was to use a small jeweler's file (if I recall correctly) and cut off the offending hang-nail.
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I would like to have a permanent solution. I am not sure whether I have damaged other threads.
 
tc1234c said:
I would like to have a permanent solution. I am not sure whether I have damaged other threads.
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Are you starting the spark plug / compression fixture your fingers? Seems like a lot of damage.

Removing the distorted portion of the thread is a permenant solution. Been there, done that. No issues since. If you can torque the spark plug you should have a good thread. If you are not comfortable with that pull the cylinder and send it to a repair facility.
 
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Geico266 said:
Are you starting the spark plug / compression fixture your fingers? Seems like a lot of damage.
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It was very tight to screw in the plug. When I backed it out a small portion of the insert popped up. I thought I have cut a piece of the thread and did not realize it was the insert (did not know there is insert to begin with). While trying to break the "chip" I actually pulled a little more of the insert coil up. Well, I will try to file off a piece and see whether the reminder of the insert/thread are still good.
 
how do you clean spark plug threads?

My bottom plugs are often tight....what is the best way to clean these threads? I bought one of the spark plug "chaser" tools from ATS but it didn't seem to want to thread in there very easily and I was too scared to force it :eek:

What do others do to clean the threads?
 
IowaRV9Dreamer said:
My bottom plugs are often tight....what is the best way to clean these threads? I bought one of the spark plug "chaser" tools from ATS but it didn't seem to want to thread in there very easily and I was too scared to force it :eek:

What do others do to clean the threads?
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With a spark plug thread chasing tool, available from ATS or any of the tool suppliers.

Are you guys putting antiseize on the plug threads? Stay away from the Champion antiseize as it dries and gums up the threads. Nickel anti-seize works great.
 
Anti-sieze

Bob are you saying that your experience with molybdenum disulfide type anti-sieze compounds (e.g., Never-Seez) is negative?

LarryT

rocketbob said:
With a spark plug thread chasing tool, available from ATS or any of the tool suppliers.

Are you guys putting antiseize on the plug threads? Stay away from the Champion antiseize as it dries and gums up the threads. Nickel anti-seize works great.
Click to expand...
 
You might try

calling around to the engine rebuild shops nearest you and asking to rent the special heli coil tool. Someone here in Tucson did that and was able to rent the tool from Varga in Phoenix. Or even better get a local A&P that does business with such a shop to approach them on your behalf. Good luck!

Jerald
-8 fuselage
Tucson
 
Nickel ??

RocketBob- In an earlier post, you mention "Nickel" anti-seize. Can you be more specific, such as a brand name, or a part #?

I have noticed that the Champion anti-seize drys up, but I have never had a spark plug stick while using it.

Wouldn't mind trying the "nickel" stuff, if I knew what it was..............:confused:
 
I've had problems with the insert coming lose in 2 cylinders over the years and I didn't like the cost of the serrated heli coils. One of the cylinders had the serrated coil, none of the rest did. I bought the regular heli coil kit ( http://www.mcmaster.com/#91732a055/=5fznev ) and it worked great. I haven't had any problems with it coming out. They're easy to install.

Kevin Belue
RV-10 flying
RV-6A flying
 
Problem fixed

Thanks for all the suggestions. This morning I went to the airport armed with a Dremel tool. Using a 90 degree attachment and a worn cut off disk (small enough to fit into the hole) I cut the damaged coil off (almost half a thread). After using an 18 mm tap to clean out the thread it looks good and works well. If you ever need to do this there are a few things you need to do:

a. put a rag in the hole before cutting. After cutting vacuum all the debris out while the rag is still in the hole.

b. coat the tap with grease so all the chips will stay with the tap and not drop into the cylinder.

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Ted,

Good to see that fix worked out for you.

For the price of the Helicoil tool you can buy a new cylinder and not have to deal with Helicoils.
 
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