View Full Version : Breaking harmonic balancer

07-13-2006, 07:43 PM
:confused: Ok, here is the problem, I have a 91 SC with 93k miles. The car runs beautiful, not a single problem, EXCEPT:mad: : It keeps BREAKING harmonic balancers. I have gone through 3 now, new ones last about 3 months, a used one lasted 2 days. I cannot figure it out, and so far, everyone i have talked to is stumped too. If anyone out there can help, i would greatly appreciate it. I only paid 100$ for this car, because of this problem, and so far have put 1100$:eek: in harmonic balancers into it.:(

07-13-2006, 07:48 PM
sounds like a crank issue hence the price of the car....
hope not though!

07-13-2006, 08:52 PM
Are you going through BHJ balancers or stock ones?

07-13-2006, 09:14 PM
It sounds like a crank issue. Here are the questions, dose the balancers fit tight onto the crank? Is the crank nice and clean? what is breaking the bolts,center bolt and or balancer? dose it look like someone was grinding or welding something on the crank? I have had 9 of these cars 4 with balencer issues. Its not impossable to bend a crank infact I have one in the garage that came from a running perfect engine but gives off a bad vibration because someone tried to weld the balancer back on because of the broke off bolt. Severe heating of the shaft will cause this. Hope this is not your problem.

07-13-2006, 09:40 PM
there is absolutely no vibration, i put a scope on the engine and there is no abnormal noises either. I am using stock balancers.

07-13-2006, 09:41 PM
oh, it is breaking the balancer itself, not the bolts. and yes the crank looks clean, with no gouges marks or weld marks. It is not even breaking the keyway, it is breaking the nose on the balancer.

07-13-2006, 09:44 PM
No vibration dose not mean all is well. It dose not take much to fling the balancer off the end of the crank. When you get a new balancer it must have the pully on it as they are balanced togeter. You must use a new crank bolt each time and I would use a little lock tight. good luck

07-13-2006, 10:42 PM
No vibration dose not mean all is well. It dose not take much to fling the balancer off the end of the crank. When you get a new balancer it must have the pully on it as they are balanced togeter. You must use a new crank bolt each time and I would use a little lock tight. good luck

At some point when a balancer broke it may have gotten jammed somehow and bent the crankshaft. If you're breaking a new stock balancer that fast something is up with the crankshaft. Put a dial gauge on the crank snout and check it for runout. You will regret the day you use locktite on the bolt if you ever break the bolt and then expect to get the broken piece out. All that is needed is to torque it to proper specs around 150 ft/lb. Good luck, John

07-14-2006, 07:48 AM
thanks for the help guys, i havent tryed a dial indicator on the end of the crank yet. I will try that today after work, and let you guys know what i get.

07-14-2006, 09:22 AM
Are you replacing the crank pulley everytime with a different one that came with the new OEM balancer????

07-14-2006, 09:51 AM
check your pulley they are neutral balanced if the weight comes off then it will be off balance and wobble . a stock balancer should last 140 k miles or more.

07-14-2006, 08:38 PM
no, i havent been replacing the crank pulley, i'ma have to check that, as stupid as im gonna feel:eek: :( , i hope that is it.:D

07-14-2006, 11:39 PM
OEM balancers / pulleys were a set and neutral balanced together. Using a different balancer and the same pulley would not balance out. A BHJ is neutral balanced by itself. Thats usually a "good" reason to get an aluminum crank pulley (neutral balanced....SC says, complete aluminum pulley set). I would do the dial-indicator and if it looks good, seriously consider a BHJ. It is all steel, and reusable and could safe you money. Otherwise, see if you can get your next balancer and pulley balanced together.

07-14-2006, 11:55 PM
I agree get the BHJ and an aluminum pulley as well as the longer bolt. its so hard to diagnose anything with the OEM balancer and bolt because they are junk. That said the car should have never gone thru balancers OEM or not like it has been....I cant see if the crank were bent you not noticeing some other problems by now...maybe maybe not I dunno....the BHJ is though by far a much better design and quality balancer though in my opinion.. I went thru 2 OEMs in 6 months then got a BHJ and had no problems again thats over 5 years now...

07-15-2006, 12:21 AM
I'm not sure if just a bad pulley would break the snout off like that. For it to break like that there would have to be a lack of support along it's length.

I'd check the dimensions of the crank snout along it's length and make sure it doesn't create a loose area that would allow for the balancer to flex and break.

Has the break been consistantly in the same place?

Note that Federal Mogul has a repair sleeve available for the crankshaft seal. Not sure how that impacts the balancer and it's snub.

07-15-2006, 07:46 AM
The stock balancer and pulley were balanced together. The rubber in your first one more then likely wore out and the other two were torn apart due to bad balancing.

07-15-2006, 02:41 PM
yes it is consistently breaking in the same place. so a bhj balancer, and an aluminum pulley? Could i buy a pulley set, and also, can someone give me a good link to were i can find a balancer, pulleys, and whatever else i may want later, if i can get this fixed shy of pulling the motor.

Also, what about this sleeve for the crank, link please?

Scott Long
07-15-2006, 03:39 PM

ASP Underdrives $180 and BHJ balancer is about $360.

ASP's are 0 balanced.

07-15-2006, 03:53 PM
you can look up the sleeve here:

I'm not sure for where it goes. As the seal rides on the balancer snout in our application.

Note I stuck with stock pullies and choose to go with the 10% overdrive crankshaft pulley from Magnum Powers. It's a nice unit and hard anodized which should give it some long life.