Harmonic Balancer Issue

[Staystash]

Hello, I'm hoping someone here can help.

Over a year ago we took my wife's L400 into the will to replace an alternator. 6 months ago daughter was driving it and said the power steering went so she didn't want to drive it. I popped the hood and see what you see in my pictures.

Only issues is we had that fixed, and the pictures here are from last night. Wife said power steering went and she thought the loose belt at the top was the issue. I looked in lower and saw the broken harmonic balancer bolt and pulley there, and washer.

Question, does this happen often? How can we prevent this from going on again? We never had this issue until that first alternator fix. The mechanic that fixed the balancer said that the only way that bolt breaks is someone messing with it. We figured the last shop did something to the balancer trying to replace the alternator.

We love this van and I personally was happy to have the wife and kids in a safe 4x4 this winter.

Thank you to anyone with answers or for just looking.

[LillianhnR27]

1. Inspect the Balancer First
Before assuming it’s junk, check for these symptoms:
•Visible wobble or vibration when engine is running.
•Cracks or separation in the rubber isolator between inner hub and outer ring.
•Drive belt misalignment or slipping.
•Unusual noises (rattling, squealing) from the front of the engine.
2. Remove the Old Harmonic Balancer
This is a hands-on step and often requires:
•Removing drive belts first (alternator, AC, etc.).
•Removing the large crankshaft bolt: this bolt is usually torqued very tight and may require a holding tool to stop the crank while loosening.
•Using a harmonic balancer puller (gear puller) to pull it off without damaging the crank snout.
3. Inspect the Crankshaft Snout & Keyway
•After removal, clean the crankshaft snout and check the keyway (the small metal key that prevents pulley slip). A damaged keyway can cause wobble after installation.
4. Install the New Harmonic Balancer
•Lubricate the threads of the crank bolt lightly with engine oil.
•Press the new balancer straight on, ideally using an installer tool — spinning it on by hand and using a nylon or rubber mallet if needed.
•Torque the crank bolt to factory specs (usually high torque — check LS400 service manual).
5. Reattach Belts & Check Alignment
After installation:
•Refit all accessory belts.
•Ensure belt alignment is straight.
•Start the engine briefly and look at the balancer for any residual wobble.
If it still wobbles, re-check:
•Balancer seating,
•Crank key alignment,
•Crank bolt torque.
6. Professional Help or Inspection
If you’re not comfortable with removal/installation or if:
•the bolt refuses to loosen,
•the crank nose looks damaged,
•the balancer still wobbles after replacement,
Quick Safety & Tips
✔ Disconnect the battery before starting any work.
✔ Let the engine cool so you don’t get burned.
✔ Never drive the car with a visibly bad or wobbling balancer — it can damage belts, sensors, and the crankshaft.