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Crankshaft Sprocket backing out?

2K views 8 replies 3 participants last post by  scaryc 
#1 ·
I brought the old talon back to life recently. Still rides like the day I bought it 10 years ago!

I swapped to injectors to troubleshoot a bad, intermittent misfire. Two of them were broken. It sure ran well with the new injectors, but the joyride didn't last long. Something suddenly didn't feel right so I parked it.

I noticed my alternator belt was split, and then noticed something stranger.

Can someone tell me how this happened and what is the best way to fix this? Why is my crank sprocket showing! :eek:

https://www.dropbox.com/s/pnlamf6mduscgof/WP_20140914_007.jpg?dl=0

Bonus pic of broken injectors:

https://www.dropbox.com/s/ivjl16l8awz4nwu/WP_20140914_002.jpg?dl=0
 
#2 ·
I'm going to take a guess here, but really you should pull the car down and remove the timing cover to inspect. The rear pulley on the harmonic balancer drives the air conditioning compressor. In your picture, it doesn't look like it lines up. This leads me to believe that your harmonic balancer is slipping off the crank snout, allowing the crank sprocket to follow along with it. My guess is that the 17mm (iirc) bolt for the balancer is either backing out or has sheered. Put the car up in the air an inspect it. Either the bolt was not torqued properly, the balancer is dead (wobbling on the crank, causing the retaining bolt to back out) or the balancer has wobbled enough to sheer the bolt.

DO NOT DRIVE OR RUN THE CAR ANY MORE UNTIL YOU FIGURE THIS ISSUE OUT. If the crank sprocket slips any more, you are very likely to slip timing, bend valves and smoke the motor.
 
#3 ·
Exactly what Cox said, Something has happened to the center bolt that holds the timing belt sprocket on. Since the harmonic balancer is bolted to the timing sprocket they both have slid out. If you haven't already jumped time you saved yourself a lot of work but get that bolt fixed then pull the cover and inspect the timing belt for damage.
 
#4 ·
Gentlemen,

Thanks for the help! I pushed the car into the garage and I'll break into it this week. I'm hoping I simply failed to torque the crank bolt properly after I had it apart to replace my hydraulic tensioner.

Hoping also, that I didn't hurt any internals.

How do you guys prefer to torque it properly without causing the engine to rotate? Can I use an impact?
 
#6 ·
OK, so I started tearing into the old talon yesterday. Now I have a concern. Since the crank sprocket is backed out, the crank pulley has no clearance. I couldn't even pull the old alternator belt off without cutting it first. How am I going to pull it off of the sprocket?

Should an impact gun be able to drive the sprocket bolt back in where it should be, without taking everything apart first? I filled my air compressor, grabbed my best 1/2 inch impact, and it didn't move at all. Any ideas?
 
#7 ·
You don't wanna just hammer it back on in case the key is out of place or anything. Your best bet is to cut the timing belt and then you should be able to rotate the timing sprocket/damper as an assembly to get it back far enough to start dissasembly.
 
#8 ·
What Sean said - Assume that your timing has jumped and that you are at the very threshold of bending valves. Even if the car looks to be in time, assume it isn't.

With the car in the garage and disabled until you start it next, pull each spark plug and drop a coat hanger into the cylinders until you know all 4 pistons are mid-bore, then back the timing gears into position after cutting the belt.. Dial the crank in SLOWLY. If you feel any kind of bind, make sure you aren't crashing the valves.

Basically, set the timing as if you were installing a fresh head. Set Cyl1's valves to TDC then dial in the crank. Once you've successfully dialed the motor back in, install the timing belt and spin it over a few times.

Locktite isn't necessary on the crank pulely if the torque is set properly, however, since setting the torque on the crank pulley is nearly impossible without turning the engine over, some blue locktite helps ensure the bolt won't slip back out.
 
#9 ·
I finally ripped into the car today so I thought would post an update!

The first few threads on the crank bolt are ruined. It took everything in the compressor to buzz it out. The key on the crank is in good shape but there is a chip in the sprocket near the keyway. The sprocket came off with a jaw puller. I ordered a new crank bolt and sprocket.

The first few threads in the crank also look suspicious.

I think this happened because I loss the proper torque on the crank bolt while I was replacing rod bearings awhile ago, since I rotated the engine back and forth during the job.
 
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