My God, this was supposed to be so easy!
After a plug blew out on me (VW Golf GTI), I did a lot of research and got hold of a Helicoil - threaded coil type insert kit. The parts of the job that I'd been led to believe would be difficult were a synch. I left the head in place and, using grease on the tap, caught almost all the aluminium swarf from the tapping operation. The few bits that got into the cylinder were easily spotted with a strong torch and extracted using a wooden splint with a dab of grease on the end (just like fishing). However, the little spring - like inserts refused all my efforts to go in properly - I followed the instructions to the letter, but the insert tool kept siezeing while the springs uncoiled and one by one got ruined. I was left with the idea that the insert tool was faulty (it has a slight burr at the end) - can't think of any other explanation for the "easy part" of the operation to fail 6 times!
OK, so others on the web swear by the solid steel inserts - I got hold of these. The tap from the new kit was needed because the solid inserts (although made by Helicoil under the name Sav-a-Thread), are a different external diameter than the spring types. Once re tapped, re cleaned the swarf out, I was again ready for the "easy bit". No such luck, the insert just got tighter and tighter on the way down the hole (I had tapped clean through so, no it didn't get stuck from lack of threads). I used an old spark plug as an insert tool (as manufacturers recommend), but it just wouldn't take the insert down flush with the top of the hole. Maybe stupidly, I got frustrated at this point and tried just putting lots more turning force on the sparkplug - it seemed to work, but when I removed the sparkplug I noticed that the knurled top of the insert (top 3 or 4 mm) wasn't inside the hole but had been squashed flat by the sparkplug! It looks just like a permanently fixed sparkplug washer. I didn't need to use the special tool to hammer the knurled part into place!
Question: is this thing gonna hold? It certainly took a whole load of force to get it in there and it didn't budge when the sparkplug was removed. Could gases escape around the edges of the insert? I used high temp thread locker - but not the recommended RTV silicone type as it was locally unavailable.
Sorry for the long post - any suggestions / feedback most welcome.
Rob