rethreading a spark plug valve

Hmmm, I've never heard of a spark plug just falling out on its own. Have you tried a Heli-coil kit?

I've seen them BLOW out -- when a sloppy mechanic cross threads them or doesn't put on anti-seize compound. Same guys who round off the oil change plug and get oil all over the exhaust and suspension.

In the situation described above, the spark plug didn't fall out on its own. It fell out because it was cross threaded.

I'd be worried about dropping the swarf into the engine - it'd be a head-off job in my mind.

I'd be worried about that too. It is amazing how much noise a little bit of metal can make in the combustion chamber. A gadget-loving lazy person could invest in a bore scope to inspect the chamber after tapping is done and try to use one of those mini-vacuums with a thin hose to suck out the swarf and debris, and if that fails, then remove the head.

If this was a Ford, I'd tell you to use a timesert insert to repair the spark plug threads (see

). On the other hand if this was a Ford, Ford would tell you to replace the head (inserts can affect the heat range of the plug and have other side effects). I am not sure of Toyota's position on repairing spark plug threads. However, if you have a loose plug, you need to do something. I personally prefer the Timesert style inserts over the helicoils and recommend that you at least evaluate their kit for your size spark plug ( ). Ed

Ive been bordering on buying one for the past 12 months, purely for curiosity lol.

We had one at the office where I worked, and when Tercels had problems with valve deposits, they were a required dealer SST. At that time, the cost was in the thousands of dollars, but they have come down to the hundreds. It would be a fun toy!

Seen them on ebay (non-camera ones, just an eyepiece and light source) for

Seen them on ebay (non-camera ones, just an eyepiece and light source) for

Happened to my wife's '97 Corolla while she was up in Mass.

Seems the local Florida dealer cross threaded the plug and it came out.

A dealer in Mass fixed it (I'm not sure what they did) and the dealer in Florida gladly paid the bill.

Aaah! The plug did not fall out on its own. It fell out because someone cross-threaded it. I have seen plugs fall out because they were cross threaded, but I've never seen them fall out on its own ;-)

Unfortunately, it is not difficult to cross-thread spark plugs in an aluminum head, especially because the steel threads on the plugs are much harder than the aluminum threads in the head and it is difficult to reach the rear bank in a transverse-mounted V-6 engine or to reach down into the tubes on some 4 cylinder engines. The trick to avoiding cross-threading spark plugs is to apply a very thin coating of high-temp anti-seize on the threads and to use a 12" length of rubber vacuum hose jammed over the top of the spark plug to start the spark plug. The vacuum hose fits tightly enough over the top of the plug to hold it, but if you twist the hose to start threading and it is cross-threaded, the hose will either slip on the tip or the hose itself will twist up. The hose also serves as an extension for fitting into awkward places.

Also good practice is to back-turn the plug a few turns which helps to let it seat properly and squarely in the thread, i find, before commencing the clockwise turning.

Im amazed the dealer would pay for something like a cross-threaded plug because theres no saying that the owner didnt take them out to check them and put them back wrong. Inless it was a matter of days i suppose.

That gives new meaning to the phrase 'getting hosed'....

I have all the work on both my Toys done at that dealership.

I would doubt they would just pay for anyone's problem, but they do trust me.

If you don't want to get hosed, you can pay $40+ for a special Snap-On tool, which is basically a hose with a handle attached ;-)

Thanks for all the help. Since it seems like something I don't want to attempt myself, I called a mechanic the other day. He said that rethreading was something that a machine shop would have to do. Is that right? Is there a sleeve or something that I can put over the plug to make it fit, instead of reathreading the valve.

I think that the guy who put this in rethreaded two of them. I tried to take one out the other day, and couldn't make it budge. What am I going to have to do about that one?

What's this Heli-coil? Will I still have to tap the valve, or is it like a sleeve that I can screw in to the valve?

I called a mechanic the other day that said that he could not rethread the valve, and that a machine shop would have to do it. Is that right?

There is no such think as a "spark plug valve" so I will assume that you are talking about the spark plug opening in the head.

The best fix for a stripped thread is to remove the head and send it to a machine shop so that some material can be added to the hold and then be re-tapped.

A way to work around having to remove the thread is to use a Heli-coil. Basically, you make the hole with the stripped thread larger and insert the Heli-coil, which is a sleeve. The Heli-coil grips the head and holds the spark plug. The problem with using a Heli-coil is that the swarf (metal shavings) from drilling can get into the combustion chamber and cause damage.

If you are having trouble removing spark plugs, I recommend that you take it to a Toyota dealer or competent independent service facility to have the spark plugs changed, making sure to tell them what is going on because you may end up striping more spark plug threads.