Helicoil repair failed

[hitmanharleyk]

2 or 3 weeks ago me and a friend did a repair on a spark plug hole and the mower ran great for 3 mowings, today half way thru it went to spitting and sputtering and I thought I had fouled a plug, when I pulled that side the helicoil came out and it had melted in half. Loaded it on the trailer to go to the shop tomorrow for what I guess is a new head, this mower is about to piss me off.

 

[Def-Ed]

Are you sure you did the repair correctly and used the correct type helicoil?
I've used helicoils on MUCH higher pressure/heat situations than that and had no problems.
My father in law's buick is one that I can definately attest too. 3.4 v6's had an issue with stripping rocker bolt threads when removed or when improperly torqued.
I helicoiled 2 while doing a lower intake on it about 4+ years ago at 40k miles.
It was passed to his sister and now has over 160k on it with no issues.

Could you have possibly used soft incorrect type helicoils? Al has a low melting point ~1400*,but still above combustion temps (obviously as the head is aluminum).

I've helicoiled several plugs in auto engines and never had an issue.
You used the correct type threadlocker right?

 

[hitmanharleyk]

Are you sure you did the repair correctly and used the correct type helicoil?
I've used helicoils on MUCH higher pressure/heat situations than that and had no problems.
My father in law's buick is one that I can definately attest too. 3.4 v6's had an issue with stripping rocker bolt threads when removed or when improperly torqued.
I helicoiled 2 while doing a lower intake on it about 4+ years ago at 40k miles.
It was passed to his sister and now has over 160k on it with no issues.

Could you have possibly used soft incorrect type helicoils? Al has a low melting point ~1400*,but still above combustion temps (obviously as the head is aluminum).

I've helicoiled several plugs in auto engines and never had an issue.
You used the correct type threadlocker right?

I used a sparkplug helicoil repair kit and no threadlocker, the kit called for hi-temp rtv silicone to be used instead so that is what I used. I can only assume a sparkplug repair kit would be good for a sparkplug repair???

 

[KennyV]

New head will be the sure & easiest repair... I quit using HeliCoils several years ago and have switched to 'TiimeSert' instead... they are perfect, and can not come out with the plug...
++ TIME-SERT Threaded inserts for stripped threads, threaded inserts, thread repair stripped sparkplug's, Ford sparkplug blowouts, threaded inserts threaded, repair stripped threads, stripped threads, inserts threaded inserts, Ford spark plug repair,
:smile:KennyV

 

[Rivets]

I will learn something new today. Can I ask a few questions? What was the brand of Heli-coil repair kit you used? They said to use an RTV sealant? I don't understand. Aluminum heads will melt at approximately 1400 degrees. Steel inserts will melt at approximately 2100 degrees. RTV sealers start breaking down at approximately 750 degrees. This is the first time I have ever heard of a Heli-coil melting in a small engine head. I have used Heli-coil and TimeSert brands and when installed correctly have not had any problems. I install both using Loctite Sleeve-Loc, to insure they don't come out.

 

[reynoldston]

Make sure your timing isn't off. advance timing will give you head problems like blown head gaskets and blown out spark plugs

 

[hitmanharleyk]

I will learn something new today. Can I ask a few questions? What was the brand of Heli-coil repair kit you used? They said to use an RTV sealant? I don't understand. Aluminum heads will melt at approximately 1400 degrees. Steel inserts will melt at approximately 2100 degrees. RTV sealers start breaking down at approximately 750 degrees. This is the first time I have ever heard of a Heli-coil melting in a small engine head. I have used Heli-coil and TimeSert brands and when installed correctly have not had any problems. I install both using Loctite Sleeve-Loc, to insure they don't come out.

Heli-Coil 5334-14 - Spark Plug Hole Threads | O'Reilly Auto Parts

I used a kit like this one and it clearly states to use red hi-temp rtv silicone before installing into the head. I asked the counter folks at O'reilly's if I should use loctite instead and they said if it recommended the silicone, that is what I should use.

Carried the mower to the shop today to have the head replaced, it is going to cost me $250+ it looks like for a new head ($100-$130) and the labor ($56 a hour for 2 hours). The shop said they had seen it before when a helicoil melted.

I asked them to look at the carburetor while they had it since it seems to need some adjusting or rebuilding, so $300 will be leaving my wallet some day late next week.

 

[Rivets]

Learned something new, thanks for the info. I don't use that style of Heli-coil, but use the style which looks like a spring, with no problem. Going to do some research on hy-temp RTV silicone.

 

[reynoldston]

I have worked on ATVs and had sealant and heat problems. Been there and did that. Permatex 81878 makes a silicone sealant called Uitra Copper good up to 700 degrees and if you are going to use a anaerobic sealer like a thread locker the best you are going to do 51031 anaerobic sealer good up to 400 degrees but be prepared to pay big $s for the 51031. Now just why are are you having heat problems with your head. Go ahead and buy a new head and if your timing is off you will just burn up the new head or what ever your problem is. I have been there with the older lawn tractors when they had ignition points one was a John Deere and just had a older cub with the same problem blowing out spark plugs. On the Cub the customer blew the plug out of the new head he has just replaced.

 

[hitmanharleyk]

Well I inherited the mower from my father and he had a terrible shaking problem, it had gotten so bad in his later life he couldn't feed himself. Other than the shaking, at 83 years old he was in great shape but his body finally wore out on him from the years of shaking because he had done it for 50 or 60 years. I'm sure the first blow plug was from him cross-threading the plug in due to his shaking and after replacing the plugs and noticing that it was bairly hanging on, we did the helicoil. I also feel it failed due to a small leak and the heat/compression/fire basically created a small torch situation at that leak causing it to melt.