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Broken off crankshaft pulley screw

During car operation, an unpleasant breakdown can occur - a breakdown of the generator pulley screw, which is mounted on the crankshaft of the car engine.
The main reason for this malfunction is a poor-quality screw, or its constriction when installing the pulley.
Broken off crankshaft pulley screw

You can repair this malfunction yourself. To do this, you will have to make some efforts. In rare cases, it is possible to crank the crease by striking a small chisel with a hammer. Most often, drilling along the axis of a broken screw is necessary. Consider the repair of the example of the VAZ engine.

Tools and materials

To dismantle the broken generator pulley screw, we need some tools:
  • electric or hand drill (wrench);
  • metal drills with a diameter of 3-5-7 mm;
  • left-hand tapered extractor;
  • core;
  • flat screwdriver;
  • fluid for stress rust and scale (WD-40).

Repair Steps

It is necessary to inspect the end of the crease, remove the burrs with a screwdriver, and treat the circumference of the broken screw with a special liquid to strike rust and scale (WD-40). This will facilitate the subsequent recess of the screw shaft.
We determine the approximate drilling depth by comparing the broken part (head) of the screw with a new screw. As a rule, it does not exceed 1.5 cm.
Broken off crankshaft pulley screw

Next, we determine the state of the end face of the breaker. It is desirable to have a flat surface perpendicular to the axis of the screw. If the surface is inclined, you need to select the appropriate drill and work a little with it. This will bring the surface to a level condition and facilitate drilling.
Broken off crankshaft pulley screw

We mount the drilling point of the broken screw. With a hardened strong drill for metal with a diameter of 3 mm (preferably domestic production), we begin to drill a broken screw to its entire depth.
Broken off crankshaft pulley screw

In some cases, such drilling is sufficient. It remains to exchange the drill for a left-hand tapered extractor, screw it into the hole and unscrew the remaining screws.
Broken off crankshaft pulley screw

Broken off crankshaft pulley screw

If the broken screw cannot be removed, it is necessary to repeat its drilling with a drill of a larger diameter. Such drilling greatly weakens the crease, and at a certain stage its removal is not difficult. Its thin walls can simply be destroyed without harming the threads in the crankshaft. After removing the crease, carefully remove all metal residues from the crankshaft.
Broken off crankshaft pulley screw


A small number of tools and skills to work with it made it possible to make a rather complicated type of repair - removing the screw flange connecting the alternator pulley to the crankshaft.

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Comments (4)
  1. Guest Vladimir
    #1 Guest Vladimir Guests February 27, 2019 18:08
    Everything is basically correct, except for one thing - THIS IS NOT A SCREW, BUT A BOLT!
    1. willow
      #2 willow Guests February 28, 2019 3:38 p.m.
      the differences between the bolt and the screw are as follows: first of all, the bolt fastens the parts passing through them through and on the other hand, the nut is screwed onto the bolt. That is, a bolt and a nut are two parts of the whole. The screw also serves to connect the two parts, but is screwed into a special thread that is on the second part. Therefore, the screw goes without a nut.
      1. Boris
        #3 Boris Guests March 1, 2019 10:59 p.m.
        A screw is a type of fastener used to fix elements and mechanisms. It is for fixing and not mounting. And wrapped with a screwdriver. His task is akin to that of a cotter pin, key, pin.
  2. Boris Khanin
    #4 Boris Khanin Guests March 1, 2019 10:52 p.m.
    The crankshaft pulley is a crankshaft pulley and not a generator!

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