Helicoil question......

[Chromequeen]

K guys, help me out please! About three months ago, I put in a helicoil into cyl head #1. She's been running fine, without incident. The other night I took her out for a ride, and she ran like normal. About a mile from home she started hesitating, and I got concerned so I decided to pull off into a well lit parking lot so I wouldn't be stranded on the highway at night. Half way across the highway she dies.... and I coast into the parkinglot. I ended up pushing her fat butt home six blocks! Uggghhh!!!

I checked the sparkplugs, and they are fouled pretty badly. When pulling sparkplug #1, the helicoil is attatched to the sparkplug, and came right out of the cylinder. It was only finger tight, I didn't need to use the socket wrench to pull it. I've not heard of this before, especially since I used the high heat (red) loc-tight on it when I installed it, and waited the full 24 hours of cure time before putting the new plug in! I was extremely careful when I threaded the cylinder, and felt I'd done a very good job. Is this normal, or did I screw up somehow? Is the red loc-tight going to hold it back in place for a while, or is the head toast now, and needing replacement? This is only a temporary fix I know, but the next owner can put a new head on it, or I'll sell it as a parts bike.......

Thank goodness that 636 is replacing this beast soon, at least I have that to smile about!

[azchick]

Wow! You can do all that stuff? Ha!
That's cool!
I am sorry you had the trouble though cq!
good luck!

[Spok]

??

I have no answer

[The Vol-can]

Wish I could help, but your mechanical ability is way beyond mine. That iis one he!! of a coil question, though.

[Chromequeen]

Come on guys, humor me!


And another question is,........ Has anyone ever used "QuickSteel" reinforced epoxy putty to mold a helicoil back into place? It says it's good up to 500 degrees, and will permanently fix aluminum, pvc, wood, etc. I'm assuming the compression from that cylinder is going to be too forceful for the loc-tight to hold it in place any longer now that it has come out fully.

[QKENUF4U]

red loctite is loosened by HEAT so being in the head its never gonna setup and hold the heli-coil permanently. dont really know what to tell ya on this one for a temp. fix. put another heli-coil in and hope for the best.
good luck

[Chromequeen]

Thanks Lance, I was told thought that the red Loctite was supposed to withstand heat... Geez!!!

[forest1000]

CQ, check the locktite site, 620 might work for you. You can ask them for advice also. I'll talk to a couple of the guys at work today. They might have some suggestions.

Dave

[Chromequeen]

Thanks so much Forest! I truly appreciate it.

[2WheelFun]

Joy...one post I read about helicoils the guy said he used 262 Loctite. Is this the same loctite you used?

[flynsouth]

CQ, you might also try some JB Weld on the helicoil. I've done that once (obviously need to be very careful not to get it on the internal threads) and it worked perfect and has held solid for about 3 years but wasn't in such a high temp/high pressure spot. I doubt you'll get a locktite product to hold as well. IMHO.

[trikebubble]

Originally Posted by Chromequeen

Thanks Lance, I was told thought that the red Loctite was supposed to withstand heat... Geez!!!

I can't help you joy, your mechanical expertise seems above mine. But i can confirm that heat is used to loosen red Loc-tite.

Here's a question, why does red Loc-Tite taste sweet like candy? Seems like a bad idea. Cleans off the fingers easy though.

[grunt]

HELI-COIL REPAIR

SPARK PLUG HOLE REPAIR KIT

Part 6 - General advice

AAC 6-58

Spark Plug Helicoil Repairs

6/95

Following a Major Defect Report investigation involving two in-flight incidents of blown spark plugs from the same cylinder position on the same aircraft, there is clear evidence a large number of approved workshops are not aware of the correct procedure for replacing spark plug helicoil inserts.

The Lycoming published procedure for replacing spark plug helicoils is detailed in Service Instruction No. 1043A. The Continental (TCM) procedure for replacing spark plug helicoil inserts is in the respective engine's overhaul manual. Lycoming in SI 1043A recommends all spark plug helicoil defects should be repaired by tapping oversize and fitting an 0.010" oversize helicoil, regardless of whether the defect is helicoil thread damage or the helicoil is loose, the TCM procedure only addresses a damaged spark plug helicoil. Thereby lies one of the problems; there is a difference between a damaged helicoil thread and a loose helicoil.

As with all aircraft defect rectification tasks, it is important to recognise the primary defect. Is it a damaged helicoil thread resulting from improper spark plug installation? Or, is it a loose helicoil resulting from erosion of the cylinder head material? Replacing a damaged spark plug helicoil with a standard size helicoil will fix the damaged helicoil. Repairing an eroded spark plug helicoil insert thread with a standard size helicoil will almost certainly result in a blown out spark plug (complete with the new helicoil).

The second issue is; not all commercially available helicoil repair kits, such as those produced by Heli-Coil, have oversize helicoil inserts. The kits may not contain the expanding and staking tool, as required by Lycoming Service Instruction 1043A and, in most cases, do not have the 0.010" oversize helicoil inserts or tap. Many maintenance organisations buy these kits from their local supplier and repair damaged or loose spark plug helicoils by simply replacing the helicoil. Again, what is the defect, what is the correct repair?

When carrying out a spark plug helicoil repair, specific care should be taken to prevent further damage to the cylinder head. Certain cylinders, such as high time cylinder heads with short reach spark plugs, are particularly susceptible to spark plug helicoil insert thread damage. Care should be taken when replacing the helicoil to reduce the possibility of further damage to the cylinder head material.

[Chromequeen]

Originally Posted by whistle clean

Joy...one post I read about helicoils the guy said he used 262 Loctite. Is this the same loctite you used?

Well, in order to make myself look like an idiot, I have to say, "I don't know...."

I don't have the package anymore unfortunately, and all I know is that the guys at the parts stores all told me to use RED loctite to keep it held into place, and now I'm ticked that this has happened. I really took a lot of care and patience in doing that helicoil, and even waited to drink a beer until after I'd done it, to make sure I didn't screw up! And now when I look at it, it seems as if the cylinder head has eroded a bit and caused damage.

Oh well, two weeks and counting till I bring that sexy 636 home!

[Chromequeen]

Originally Posted by flynsouth

CQ, you might also try some JB Weld on the helicoil. I've done that once (obviously need to be very careful not to get it on the internal threads) and it worked perfect and has held solid for about 3 years but wasn't in such a high temp/high pressure spot. I doubt you'll get a locktite product to hold as well. IMHO.

Hey thanks. I was going to use that, but the cylinder head itself now has a bit of damage, so I'm going to have to try and repair the hole in order to reinsert that helicoil. So now it's lookin' like I'm gonna use the QuickSteel since it says it permanently bonds to Aluminum, brass, copper, steel, etc. It says Great for marine use, and fixing motors and cracked manifolds so I'm gonna at least try it, what have I got to lose at this point, ya know? I'll sell the brat as a parts bike if I have to.........

[Chromequeen]

Originally Posted by trikebubble

Here's a question, why does red Loc-Tite taste sweet like candy? Seems like a bad idea. Cleans off the fingers easy though.

Well, I'm wishing at this point they'd have given more clear instruction as to what it was used for. After licking the package I have to use the blowdryer to clean off my lips, and my face is blistering from the intense heat of trying to remove it!

[Chromequeen]

And thanks Grunt for that article, it is very informative!

[rbentnail]

Parts of the difficulty with locktite and helicoils:

a) yes, locktite is loosened by heat but the "red" is good to about 450*F.
b) petroleum products of any kind- in the new threads, on the helicoil or your fingers, anything anywhere- will keep the loctite from setting up properly. Everything must be thoroughly cleaned with alcohol, preferably aerosol alcohol like electrical contact cleaner.
c) helicoils are tempered steel to make them "springy"- They will work well in high, low or normal temperatures. But large temperature swings as experienced in the cylinder head, remove the temper causing loss of spring and thread tension, thus it screws out. Threaded inserts work much better for varying temperatures.
d)there are several different grades of red locktite. Auto stores carry one. Check with an industrial supply store instead. Look for 272. D**n near permanent and withstands the heat better.

If the threads aren't too bad try another helicoil. Some type of liquid or putty epoxy will work- I like a brand called Pig Stik. It's a putty type rather than liquid, and after it sets up, it works (drill, machine, etc.) like soft metal, but it resists heat, oil, wear, etc. Best stuff I've used in 20 yrs. of maintenance work. Used it on electric motor shafts, inside hydraulic cylinders and gasoline & diesel fuel systems, on radiators and forklift engines.

Also- be sure to use antiseize compound on the spark plug. This will help keep the coil/insert from sticking onto the plug.

Again, whatever you decide, everything must be thoroughly cleaned with alcohol before application. This is most critical, and often overlooked. Good Luck!

[forest1000]

CQ,

Checked with a couple of guys here. Ignition temps are around 1300°F, so you need to get some LT that withstands this temp. They say to check at the local auto supply stores because there is supposed to be some that will do the job.

Beware, though once this stuff sets, nothing is coming out.

That's the best info I can get right now. If anything else comes up, I'll let you know.

[Chromequeen]

rbentnail, you have made some very wise comments, and also made me feel a bit more secure in what I did in the process.
I had read hours of info when trying to decide if I was mechanically inclined enough to handle this, and you're right. Petroleum based anything would definately be a hinderance in this procedure for sure.
The steel based apoxy putty that I found should work. It sounds like it is the same type of substance that pig stik is. I'll try this and see if it works.
Thanks for your help!