How to lock crank shaft while torquing central screw?

Question

It seems I have to replace the oil seal at the pulley-side of my crankshaft. According to the technical manual of my car, the central screw should be torqued with 120-145Nm.

I don't know how much torque is needed to crank my motor, but I guess that 120-145Nm is enough.

So, how do I prevent it from cranking?

The technical manual recommends several special tools for many different tasks, but there is no tool for this purpose. I don't have an impact wrench, and this should usually not be used to torque a screw to a given value.

Answer 1

There are a few different ways I can think of to do this:

If the vehicle has a manual shift transmission, put the transmission into the highest gear, then set the parking brake. The torque provided through the drivetrain will be more than enough to counteract the torque put on the crank hub bolt. If it's a front wheel drive, have someone stand on the brake pedal, or wedge something onto the brake pedal to hold the front rotors still.

Another way, if it's not a manual shift tranny, is to take the starter out. Then using a long, stout, flat tip screwdriver, find purchase against the starter ring teeth. This obviously requires a friend to hold it in place, but I've found works rather well if you can find purchase. If you cannot find purchase, you may be able to wedge something into the teeth to do the same ... just remember, you have to take it out after you get through torquing the bolt.

If you have an old serpentine belt, you can wrap it around the crank shaft pulley, grabbing it tight with a pair of Vise-Grips right at the pulley. Then string the other end over another pulley (not the tensioner pulley), grasping that side with another pair of Vise-Grips. As long as the belt isn't completely worn out and you can get a good enough grip with the Vise-Grips, this will hold it for you as well.

EDIT: I came up with this diagram to help you with understanding the above reference:

The blue arrows are the pinch points with the red line being the belt.

If these don't work or you cannot get them to work, maybe they will lead you to another way you can get it to work.

Answer 2

An old trick for this is to remove a spark plug, then feed a length of string into the cylinder through the spark plug hole, leaving enough string hanging out to pull it all out when done. The string won't compress, so stops the motor from turning, allowing you to tighten the crankshaft bolt. When you're done, remove the string by pulling it back out the hole, and re-install the spark plug.

The process is shown here. (Not my video)

Answer 3

This is what I have used for years, Snap-On (Blue-Point) adjustable joint pliers, the large variety. Pn HL120P

I usually leave the crank pulley on and use that to grip with pliers, most crank pulleys neck down to a smaller diameter than the harmonic balancer, since the pliers only go to about 8".

Sometimes it is hard to hold the pliers on bolts torqued over 175 ftlbs, so i let the pliers turn with the crank and let them hit the frame or steering to help hold the pliers, this way I can get more muscle on the bolt with my break over bar.

Another method to remove the bolt, that works on any engine that turns clockwise (looking at it from the front) (not some Honda's) is to use a long breaker bar, put it on the bolt and rotate the crank clockwise to the left side of the engine and let the beaker bar hit the frame or steering, hold it there while some one taps the starter, this will break it loose. I know it sounds scary but I have done it for years without anything bad happening, just have someone you trust on the ignition key that knows how to tap the starter in short bursts, best to disconnect the ignition system before tapping the starter.

Best solution is a Piston stop