The whole thing is rather strange. I wouldn't expect those temperatures to crack the plugs. Are there any other issues that may be involved that may be getting the exhaust manifold'* temperature a lot higher than normal?

Before reading this post from me..understand this is total speculation and I'm putting it out there for ideas only.

Thinking more and more about this..... the plugs are cracking in this car too consistently to be a fluke. We haven't seen others with this type of issue, with this consistency.

I'm starting to wonder..if voltage through the plug wire is too high or too low...could that heat up and crack the plugs?

Say either battery/battery cable or coils/icm somewhere has an issue and is off.

After seeing the condition of the wires this weekend, I have been considering them as a cause as well, although I'm not sure what they could be doing to cause this. I haven't had any electrical issues for a few months (turned out to be a bad postive battery terminal connection) that would indicate a charging system problem. If there were, I would expect voltage spikes and blown fuses. I'm not ruling it out, I just don't know where to look for the gremlin off the top of my head.

A clogged cat could cause the manifolds to overheat, but I have seen no signs of that from the computer, emissions tests, or any running issues that might indicate a bad cat. I have also never seen the manifolds glow red as would be expected if they were hot enough to cause damage.

Having recently run some electrical gremlins out of my car..I can say. It'* not that bad to follow the battery cables and clean all the ends and connections. That'* step 1.

I tried to find a similar thread over at CGP about one guy having the same problem. The problem was supposed to be cured when the plug wires were replaced.
I hate it when I can’t find something that was there earlier.


Her is what I got.
http://www.clubgp.com/newforum/tm.as...de=&*=#3051569

Maybe it was over at the Regal forum I don’t know but I wish I could find it. Gurr

If you are good with SEARCH please see if you can find that old post.

Thanks Ron...glad to have more input. This is a stumper of a problem.

This link is to a page showing the spark end of the plug, and what it means. Anything look similar to what you found with the plugs?

http://www.gnttype.org/techarea/engine/plugs.html

Other searches didn't find a lot. Here'* a good page on knocking and pinging, which can cause the plugs to crack.

http://www.cars.com/carsapp/usatoday...knockping.tmpl

The only other thing I could find was on using too hot of plug. The plugs would retain too much heat, and also lead to detonation, which would contribute again to the cracking.

This is not the post I was looking for but it talks about plug wires and cracked porcelain.

http://www.clubgp.com/newforum/tm.as...heck=500070287

Those pictures are all showing the business end of the plug. The cracks I am getting are on the insulator at the top of the plug. Detonation is a possibility though. I wonder if a properly located knock could shock the plug enough to crack the insulator near the wire. That combined with excess heat may do the trick.

So a bad coil can cause this? That'* worth a look too, although my problem seems to be wandering around the engine. That guy had the same cylinder every time. And he could reproduce it on demand.