Cracked Spark Plug

evil821 · February 13, 2011

Has anyone ever experienced a plug cracking? I have an '09 Denali, had the plug in #8 crack 3 times in 5.5 months. Also loosing coolant, dealer cannot come up with a solution for either, latest attempt, switched coil, plug and injector with 3 different cylanders, now just a matter of time until issue occurs again. Claims no coolant on plug when pulled. It's not on my drive.

Any thought?

00Silverado4x4 · February 13, 2011

Initial thought but the plugs might be over torqued when installed. It doesn't take much to crack a plug on install. I've done it more time than I can count. Also check around the area to make sure there is nothing that might be bumping into the plug. I don't have any ideas on the coolant loss but there is several topics discussing coolant loss here. I'd try a search & see if any of them might help you out.

GMstrong · February 14, 2011

How is it cracking the tip of the plug or threads?

8.1HD/ALLISON · February 14, 2011

Never heard of that issue. On the coolant loss, cracked heads? I don't know what the year range is on the head issues.

evil821 · February 14, 2011

The ceramic has cracked on each occasion. The car is an '09 and has 21K on it and the issues started at about 16K. The problem has occured at start up and while driving. I hope a trained tech has not over torqued the plug that many times.

jdubub · February 14, 2011

sorry to hear about this. do you have any pics of one of the spark plugs to put up?

vettelovralexand · February 14, 2011

I would say find a new dealership to take it to. If that doesn't work, GM can just buy you a new engine which doesn't have that problem. That is what warranties are for.

GMstrong · February 14, 2011

I dont if its just me but your not a "trained tech" if you cant put a spark plug in right without over torquing it but you them dealerships they love impact wrenches.

ChevyTech77 · February 14, 2011

Last I checked, you aren't going to crack the porcelain part of the spark plug too easily, by over torquing it. It certainly can happen from mis-handling the plug prior to installing it, quite easily. Possibly even from thermal shock (hot to cold, or vice-versa, quickly). Besides, try and think about it logically, how is it making it out of the shop without missing if the damage is done upon installation?

How much coolant loss is there?

evil821 · February 15, 2011

Last I checked, you aren't going to crack the porcelain part of the spark plug too easily, by over torquing it. It certainly can happen from mis-handling the plug prior to installing it, quite easily. Possibly even from thermal shock (hot to cold, or vice-versa, quickly). Besides, try and think about it logically, how is it making it out of the shop without missing if the damage is done upon installation?

How much coolant loss is there?

It is a slow loss on the coolant, it is my wifes vehicle so I am in it on rare occasions. It has been an issue since 6K. The pressure tested and stated system was fine. I would say I have had to fill it 5-6 times. It has overheated at least once. They claim if it isn't on the plug, it can't be a head gasket??? It's pissing out somewhere.

They have a picture of the plug at the dealership, they have admitted that they are not sure what the issue is, now a GM engineer is suppose to come down to figure it out, which will be damn near impossible since when it is hooked up after plug and coil replacement it looks fine.