My daughter's 97 GMC Sonoma (4 cyl) truck has a spark plug problem - cylinder #3 plug will break and the ceramic insulator part will move up and down the plug throwing off the gap and causing a cylinder #3 misfire code to be set - car runs like crap. This has happended 2, maybe 3 times in the last year - runs fine in between this. I also have a pool of coolant that is collecting in this spark plug well - right where the plug screws into the head. Any suggestions?

ryan

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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

You have a hairline crack in the cylinder head. The heated spark plug coming in contact with the coolant probably causes the ceramic jacket to crack. Until that head is replaced, this will continue to plague that vehicle.

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

if you dont want to keep the car forever, one could try some of the miracle in a bottle cures for heads-gaskets. i once ran a ford ranger for 20k plus w/ a blown HG on 2 tubes of alumaseal. sent it away for other reasons.
not that i would recommend plugging up your cooling system.

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1984 123.193 372,xxx miles, room for Seven.

1999 Dodge Durango Cummins 4BTAA 47RE 5k lb 4x4 getting 25+mpgs, room for Seven.

Verify that the heater hose routing is either away from this location, or if overhead, that the heater hoses and their connections are not leaking.

Thank you for the replies - I was assuming the worst and I think I am going to have to pull the head (fortunately, they are not very expensive for this vehicle). Heater hose is not causing this... so either the head is cracked or the gasket is blown - but I'm not sure how I would get coolant where I'm getting it if just the gasket was bad.

I really appreciate the help!

Ryan

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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

This is a "get by until you can have it fixed" idea:

If the leak is small/slow, you may be able to protect the spark plug by wraping foam around it. Maybe use the foam that is in spark plug sockets that holds the plug in position. You may need to run a cooler plug in that cyl.

Find out for certain where the coolant is coming from, it shouldn't be hard. The sparkplug thing is a symptom, not a cause. Remember that coolant under pressure can spray in a small stream for good distance, easily from one side of the engine compartment to the other. Pressure check the system both when cold and when hot, preferably watching it go all the way from cold to hot and back again, and watch for coolant to drip, spray, seep into that sparkplug recess. Good luck.

MV

My wifes car kept breaking a spark plug. I had a spark plug reader look at it, he said it was cause of a bad injector.