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question 95 impreza crank bolt


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12 replies to this topic

#1 86subaru

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Posted 25 November 2012 - 02:44 PM

crank bolt came off while driving lost belts, bolt came all the way out , my question is any damage done , ? it starts and moves ok, lost key also, 2.2 a/t awd, sedan

#2 davebugs

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Posted 25 November 2012 - 03:29 PM

Someone didn't button it up properly last time.

Depends on how bad keyway is how screwed you may be.

#3 johnceggleston

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Posted 25 November 2012 - 03:29 PM

no internal damage. just whatever the flying parts may have caused.

replace the missing pieces and any damaged or mutilates pieces, like the crank pulley and the crank sprocket.

the keyway in the crank may be mangled, but it should go back together and run right if you line it up correctly and torque it to 137 ft. lb.
also a good time to replace the timing belt and anything else needed inside the timing cover.

when was the timing belt last done?

this thing came apart because the bolt was too lose, not torque to spec. if you do not replace any mangled parts, except the crank, and if you do not torque it to spec, it MAY cause a repeat failure.

#4 86subaru

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Posted 25 November 2012 - 05:36 PM

15,000 mi ago on timing belt, key way is gone no spare, but spare spocket

#5 dangordon0128

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Posted 13 December 2012 - 10:01 AM

Mine came out on both my subaru's. The one where the key was a little warped but everything else looked good: new belts, new pulley, new bolt, blue loctite, 140 pds. The other needed a new timing sprocket and key, but the same routine. Luckily, both keyway's were not mangled and the position of the timing sproket was not compromised. I check the bolt at EVERY oil change.

#6 ivans imports

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Posted 13 December 2012 - 11:58 AM

new key new reluctor gear and new pully when you repair it check the crank for being worn down on end have had good luck peening the end of crank to fatten it up so pully fitts tighter

#7 mikec03

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Posted 13 December 2012 - 04:30 PM

Just so everyone realizes that owns a 95-99 2.2 subaru, the 137 ft-lb torque is way, way over the original spec for the 95. The bolt probably loosened because the mechanic followed the original spec which was in the 70-80 area. I torqued my 95 to 140 ft-lb, and in addition, I put a white mark on the bolt and the pulley just to check if it was loosening up. From 95 to 99, subaru, recognizing the problem, constantly increased the spec torque.

#8 ivans imports

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Posted 15 December 2012 - 07:53 PM

i think the problem is the lack of a good way to hold the flywheel to get enuff tourque on the pully bolt. I biult a plate to lock the crank to tourque the bolt.

#9 mikec03

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Posted 16 December 2012 - 08:38 AM

Holding the crank pulley with a tool is of course the best way to tighten the crank bolt. However, I easily held the motor with a 8" shank, 3/8" sq, screw driver inserted into the flywheel inspection hole. There are slots in the flywheel, at least for the 95-99 cars, which you can position the screwdriver. The mechanical advantage is maybe 7/1, the flywheel is about 1' radius, so it only takes 20 lb force to hold the engine rotation against the 140 ft-lb torque.

#10 avk

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Posted 16 December 2012 - 11:14 AM

The older torque specification may have been too low, but, if memory serves, there have been no cases of a factory-installed bolt loosening up. If true, this leads me to believe that replacing the $5 bolt would be a very reasonable precaution.

#11 Fairtax4me

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Posted 16 December 2012 - 12:26 PM

Holding the crank pulley with a tool is of course the best way to tighten the crank bolt. However, I easily held the motor with a 8" shank, 3/8" sq, screw driver inserted into the flywheel inspection hole. There are slots in the flywheel, at least for the 95-99 cars, which you can position the screwdriver. The mechanical advantage is maybe 7/1, the flywheel is about 1' radius, so it only takes 20 lb force to hold the engine rotation against the 140 ft-lb torque.


You got it backwards. 140 ft-lbs of torque is exactly 140 pounds of force applied to the end of a 1 foot lever. Your mechanical advantage is that you use a 2 foot breaker bar to turn the bolt, so you only push with 70lbs of force, 2 feet from the center of the crankshaft.
The hole in the flex plate is only about 6 inches from the center of the crankshaft (if that). 140 ft-lbs at half of a foot means the force applied to the screwdriver doubles. The screwdriver has to hold 280 lbs.

A good screwdriver is able to hold this. A cheap Chinese screwdriver may break.

#12 mikec03

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Posted 16 December 2012 - 06:54 PM

Fairtax4me

You misunderstood my point. The mechanical advantage occurs by comparing the distance from the edge of the flywheel to the housing, versus the length of the screwdriver outside the housing. The overall length of the screwdriver is 12". If the distance from the flywheel to the edge of the housing is 1", and I push against the turning force 1" from the end of the screw driver, then the mechanical advantage would be 10/1.

In any case, the important point that I wanted everyone to know, is that one person can easily hold the flywheel while pushing the torque wrench at 140 ft-lb on the crank bolt with the other hand. In short, it doesn't take much strength at all.

Also, as a matter of fact, I did change crank bolt because I was afraid that the original bolt wasn't high strength. But the old and new bolt were identically marked. And finally, I have seen posts of crank bolts loosening so it must have occurred at least a few times.

#13 Gloyale

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Posted 16 December 2012 - 07:49 PM

One word:

Loctite (Or a good quality RTV like RightStuff)

That way even if you can't hold the crank super tight for perfect torque, the bolt will be unlikely to vibrate loose.




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