Timing Belt Slips / Plug Failure
sbmunds
06-30-2005, 09:23 AM
The wife reported a low idle on the Sportage one afternoon. The next morning, within 1 mile of the house, the car stranded her on the side of the road ... lots of "weird" loud noises, barely running, etc. Knowing the 60k timing belt replacement recommendation (ours has 76k ... I know, I know) and having read a few of these threads, I immediately suspected the timing belt, especially after hearing the engine as she turned it over. The thing spit and sputtered and wouldn't fire at all.
I finally got the front of the motor apart and the original belt looked OK, but in my haste, I didn't think to check if it had slipped a few teeth. Nonetheless I replaced it. Manually turning the crank and cams during this process was effortless, no abnormal movement or noises. I tried to crank the engine after reassembling the front end, but the same rough, even violent, cranking remained. It was then I noticed the front plug arcing and popping from under the front of the black plastic cover on the top of the head.
I removed this access panel and noticed that the plug wire was off of the plug. I reseated it and turned the engine over again--no change. I then noticed the third wire was also off of its plug. I reseated it and tried again. Within a few revs of the motor, both plug wires were blown off their plugs--Somehow, combustion chamber pressure was leaking up into the head cavity where the plugs are. But, this being my first OHC engine, I wasn't sure how. Short on time and patience, and fearing more significant damage, I sent the car to a professional. They eventually found that one of the plugs under one of the coils had either failed altogether or been pushed up out of the head by something--It had cratered its coil above. They borescoped that cylinder but couldn't see anything. Removing the head, they found a blown head gasket, but no further mechanical damage. They did report that the brand new timing belt I had just installed (strictly per the service manual's instructions) was "way off."
So, can anyone guess as to the sequence of events that could result in this damage, and can the violence and rough cranking (on essentially one cylinder) be enough to force the timing belt to slip some teeth?
I finally got the front of the motor apart and the original belt looked OK, but in my haste, I didn't think to check if it had slipped a few teeth. Nonetheless I replaced it. Manually turning the crank and cams during this process was effortless, no abnormal movement or noises. I tried to crank the engine after reassembling the front end, but the same rough, even violent, cranking remained. It was then I noticed the front plug arcing and popping from under the front of the black plastic cover on the top of the head.
I removed this access panel and noticed that the plug wire was off of the plug. I reseated it and turned the engine over again--no change. I then noticed the third wire was also off of its plug. I reseated it and tried again. Within a few revs of the motor, both plug wires were blown off their plugs--Somehow, combustion chamber pressure was leaking up into the head cavity where the plugs are. But, this being my first OHC engine, I wasn't sure how. Short on time and patience, and fearing more significant damage, I sent the car to a professional. They eventually found that one of the plugs under one of the coils had either failed altogether or been pushed up out of the head by something--It had cratered its coil above. They borescoped that cylinder but couldn't see anything. Removing the head, they found a blown head gasket, but no further mechanical damage. They did report that the brand new timing belt I had just installed (strictly per the service manual's instructions) was "way off."
So, can anyone guess as to the sequence of events that could result in this damage, and can the violence and rough cranking (on essentially one cylinder) be enough to force the timing belt to slip some teeth?
Automotive Network, Inc., Copyright ©2026