I was driving my car on Saturday (96 Civic) when suddenly, I heard a popping sound coming from the engine bay. As I was pulling over to the side, I felt a thud and I saw the crank shaft pulley fly off! I couldn't believe my eyes, how does a crankshaft pulley just come off. The AC compressor, power steering, generator all stopped working. The engine was still running. I just picked up the pulley, removed the drive belts and drove back home. Couldn't find the missing pulley bolt.
When I reached home, I realized how close I came to ruining the engine. The camshaft pulley and bolt is the only thing that holds, the timing belt pulley in place and I was extremely lucky it didn't fall off while I continued driving.
At home, I inspected the pulley, there is a notch in the pulley that has taken a slight beating, and the splines on the pulley look worn. I took some pics, it was dark so things are not very clear. I also inspected the part from where the pulley came off. The outer part of the thread seems slightly stripped, the inner looks ok. But there is a broken bolt stuck in there.
Took the car to the workshop on a recovery vehicle on Sunday. My mechanic told me this is not the first time he has seen a crankshaft pulley bolt broken. He's worked on two other vehicles with broken crankshaft pulley bolts. In both cases the car was a 96-2000 Civic. Mine is the third one. On the first car, the engine had to be pulled from the vehicle to get the bolt out, lucky for the owner. In the second case, they had to remove the crankshaft, take it to the machine shop to get the broken bolt out. The timing belt was changed a few months back so my mechanic is hopeful that the threads will not be jammed, hopefully he will be able to drill it out. Slap on a new pulley and bolt and all will be good. So right now just hoping for the best.
I was looking into the service manual and thinking that maybe the bolt needs to be replaced, every time the crankshaft pulley is pulled but there is no such instruction in the service manual. With 260,000kms on the engine this bolt has been removed 4 or more times for timing belt change. It's not an easy bolt to remove. I guess the stress of removal and re-tightening with desi torque might have resulted in metal fatigue which finally broke it. So it might be worthwhile to replace the bolt every time one is doing a timing belt job.
The thing that is bothering me is that the check engine light came on the day before this incident and it stayed on the whole day. I've had this car for more than 10 years (264,000 km on the engine), the CEL has never been on before. Anyway, I disconnected the battery for 30 seconds, but it did not go away. I thought I would get it checked on Monday. I continued driving with the CEL on all the time. Could the CEL be related to Crankshaft speed fluctuation (CKF) sensor or Crankshaft position CKP sensors? Could the two incidents be related in any way? I can't seem to make a connection.
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