Hello friends. Its me again. For the backstory on this 1996 Honda Accord V6 AT Sedan saga; harmonic balancer woes .

In short, we repaired the engine and got it started. It actually started right up after sitting for two years. Amazing! Unfortunately, the brand new pulley bolt would not hold. Once again it came off, and could not be torqued to spec having stripped the threads in the crankshaft snout, in spite of chasing the threads with a tap. Too many of the threads at the end of the snout were missing for the rest of the treads to hold.

My question: is it possible for a machine shop to repair the end of my crankshaft without removing or replacing it from the engine? There is a M16 x 1.5 Time-Sert and Heli-coil thread repair kits. Alternatively, it can be tapped up to a size M17 or M18 with a matching bolt fabricated by a skilled machinist?

Has a crankshaft thread repair like these ever been done successfully? Anyone have direct actual experience or reliable anecdotal evidence?

This engine is old and worn enough not to warrant the replacement of a crankshaft, or the replacement of the entire engine since to do that correctly costs more than the value of the car. My hope is to get it to work for the life of the new timing belt and water pump that I installed, even if it means I have to have the bolt permanently welded onto the crankshaft for as long as the belt will last,

Its taken me a few months time to decide if I should even bother you with this lost cause, but the fact is that everything that was accomplished up to this point has seemed to work with flying colors. Frankly I was amazed how it started right up like it never sat a week. Nevertheless, like before, that harmonic balancer bolt just would not ultimately hold without addressing the damaged crankshaft snout threads. It needs more steel thread than the loctite can manage here. It just won't torque to spec any longer.

Once again, this thread has photos and shop manual diagrams. You can see the condition of the snout after my: Ghetto Timing Belt Job .

The lesson is that harmonic balancer bolts should ALWAYS be removed with the correct tool when replacing that timing belt! Or else, a cascade of damage and woe will possibly ensue. Also, don't hire the wrong mobile mechanic (or hack)) for that job. If they don't have the required tools, they are not the mechanic you need.

Thanks in advance for any input or advice. I am prepared for "I told you so" and will assume the position for any hazing if it leads to a good next thing to try without removing or rebuilding the bottom of this engine. I am willing to let a machinist (or welder) do the job if it makes sense to do that at all with the crankshaft still in place. The Time-Sert M16x1.5 Kit costs $220 not including the longer (32mm) coil insert, plus tax and shipping. A machinist will need that up front, I imagine.

CRANK shaft snout after broken harmonic balancer bolt was removed from 96 Accord V6


I hope this documented experience will be useful to others seeking answers, nevertheless.

Thank You

Bob Who
(or Boo Who)

 

You already know that it'll be a sketchy solution at best.

It's difficult to speak for the capabilities of any machinist or mechanic... but here goes.

I think that any kind of welding on the end of the crankshaft will leave it warped one way or another. I worked on a project with welding sections of tubing with very critical alignment. We had to make so many trial sections just to develop the welding technique to end up with a very straight tube. That's like grabbing 6 crankshafts from a junkyard to practice before trying it on the "real thing".

Enlarging it to a non-standard size (like M17-1.5) probably means you won't find a hardened bolt. A machinist fabricating that bolt probably means it'll be softer and will not last very long even if the crankshaft is threaded properly. That leaves a helicoil or timesert and using the original bolt.

In order to use a helicoil or timesert, you'll have to align the tap carefully straight & true which is more difficult to do in-place. How easily can you thread the pulley bolt into the mangled threads? If it's difficult to get it started into the threads, then it'll be even more difficult to line up the tap and get it started straight. And I bet the crankshaft is made of tougher material than the normal stuff that helicoils are used for.

Then there's the issue of it being balanced (or not) after you get the helicoil in and the pully installed. The need for a harmonic balancer within the crank pulley is a clue suggesting the need for this to be nicely balanced when you're done.

It might work, but the chances of it NOT working might be 50/50. You might want to shop around for a used engine to swap,

 

I would not tap a bigger thread, because I don't know if you could find the correct bolt.

You may get away with a timesert. It would be much cheaper than replacing the crank. Just find out what the timesert is rated for torque, because the spec on the bolt is ~150 ft-lb.

 

Thank you JimBlake, PAhonda, and Forum!

I appreciate all the thoughtful follow-up on this. I agree it's risky enough without fabricating the wrong bolt. If I find the right machine shop, I may move forward with Time Sert. For the record, when I inquired to Time-Sert directly this was their reply, which may be useful information:
I'll keep you guys informed of any success or failure. Meanwhile, if you don't hear otherwise, I think we've beaten this dead crankshaft long enough for others to learn from the experience. I think that everyone here and at Time-Sert has given me the best information, and I am very grateful for that. I don't regret these facts one bit because I am confident I really am well-informed. The current situation, reality, is better than fantastic expectations or poor analysis of cost/risk. As expensive as installing a new crankshaft or rebuilt engine would be, it does not improve the bottom line to invest more time and money on a coin flip. 50/50 may be better odds than a casino, but it's not good enough for auto repair. If I had investigated before hiring a cheapo mobile mechanic, then I could have saved enough to afford a guarantee from a shop with real tools.

I could have saved enough to hire a mobile dentist instead…or just go to Vegas to look at some headlights.

Thank you, very much!