Should I Replace The Harmonic Balancer?

MikeO

MikeO

TJ Enthusiast
Supporting Member
Joined
Jul 22, 2017
Messages
157
Location
Hallsville, Texas
Not a Mechanic here, so...
First of all, is a harmonic balancer the same thing as an Engine Crankshaft Pulley?
Secondly, I am replacing the cooling system from the water pump forward and I ran across a video that claimed the harmonic balancer can come apart after a few decades.
Should I replace that while the Jeep is apart?
Thanks.
 
The crankshaft pulley is part of the harmonic balancer.
Inspect the rubber sandwiched between the outer weight and the crankshaft mounting hub looking for cracks or movement of the weight inward or outward off the hub.
Since you will have the radiator, thermostatic clutch, fan blade and water pump removed along with the serpentine belt; it would be a good time to replace the harmonic balancer.
 
  • Like
Reactions: Flivver250 and MikeO
CharlesHS said:
The crankshaft pulley is part of the harmonic balancer.
Inspect the rubber sandwiched between the outer weight and the crankshaft mounting hub looking for cracks or movement of the weight inward or outward off the hub.
Since you will have the radiator, thermostatic clutch, fan blade and water pump removed along with the serpentine belt; it would be a good time to replace the harmonic balancer.
Click to expand...

Thanks!
 
Agree. I did this in my 05 TJ last couple years. It’s not complex, with rent a tools etc. It is tight, doing it without removing all that stuff like the radiator etc took creativity. Ha.

If that’s all out, I would replace it, I don’t recall that being expensive, if it looks time.
 
I did mine on my 97 when I went after the timing chain. I did the water pump, new thermostat housing at the same time.

Should have done the hoses...looked good at the time but the lower is now dripping.

Also should have bought a cam spring and spacer...mine was either missing or disappeared into my gravel driveway.

https://www.cleggengine.com/engine-...ar-bolt-pin-and-spring-by-cleggs-ce-jcgb.html
That's a 97 only part.

-Mac
 
  • Like
Reactions: Flivver250
MikeO said:
Secondly, I am replacing the cooling system from the water pump forward and I ran across a video that claimed the harmonic balancer can come apart after a few decades.
Click to expand...

So yes, that can happen as the rubber dries out and breaks down. As the rubber becomes hard, the damper becomes less efficient at its job, and can eventually separate. I've seen plenty of decades old units running, and I've only seen one come apart on the drag strip. So if you're having weird vibration issues, or you can see damage to the rubber, replace it. If you just want to do it for peace of mind, go for it. If you're tight on cash and it checks out ok, then it's likely safe to return to service.

Personally, I'd replace it if I need to pull it for something like a timing chain job, probably not if I didn't have to pull it off for the current job.
 
  • Like
Reactions: MikeO
BlueC said:
So yes, that can happen as the rubber dries out and breaks down. As the rubber becomes hard, the damper becomes less efficient at its job, and can eventually separate. I've seen plenty of decades old units running, and I've only seen one come apart on the drag strip. So if you're having weird vibration issues, or you can see damage to the rubber, replace it. If you just want to do it for peace of mind, go for it. If you're tight on cash and it checks out ok, then it's likely safe to return to service.
Click to expand...

We are starting to see more failures now that are bothersome. I'm just about at the point where a replacement will become part of any normal maintenance.
 
  • Like
Reactions: g.hayduke and BlueC
mrblaine said:
We are starting to see more failures now that are bothersome.
Click to expand...

Interesting. Are these old factory units or aftermarket replacement units that are failing? Any obvious reason for the failures?
 
BlueC said:
Interesting. Are these old factory units or aftermarket replacement units that are failing? Any obvious reason for the failures?
Click to expand...

No idea about any of that. I just know that up until about a year ago, we never saw one that had failed and now I've seen 3 in the last 6 months.
 
  • Like
Reactions: BlueC
Just ordered a Harmonic Balancer PN 33002920 for my spare parts cabinet.
In the 20+ years that I owned the my '98 XJ 4.0L; I needed to replace the harmonic balancer once.
A Jeep Tech friend and I replaced both the harmonic balancer and the timing chain cover crankshaft seal at the same time.
 
BlueC said:
Interesting. Are these old factory units or aftermarket replacement units that are failing? Any obvious reason for the failures?
Click to expand...

I'll just speak to my 2005 which is anecdotal.

I had a squeak with the belt. Hit it with water, goes away 30 seconds later it came back. I chased some parts that looked old, the pulley etc, and a new belt, and didn't help. Then saw a thread on the Harmonic Balancer. Sure enough, mine was just enough out of alignment that it looked like it was "just off" some. Not catastrophic. I pulled it, and it looked to be the original from what I could tell. Just "that time" that the rubber was running into an end of life. That was July 2020 at 109,790 miles (I've got a decent log book my German mom trained in me).

Lots of factors could wear into that, this is a Texas Jeep, I don't know if cold and salt or heat and dust or whatever would contribute to it happening faster, but that's the timing of mine. It's worth a maintenance look, I have no idea if it will "just blow" on someone, but at least for me it gave a warning squeak and let me get to it.
 
mrblaine said:
We are starting to see more failures now that are bothersome. I'm just about at the point where a replacement will become part of any normal maintenance.
Click to expand...

We’re the three running a belt driven onboard air compressor?
 
This one drove me nuts until realizing the balancer had spun internally due to the degraded rubber bond, lines show actual spun TDC mark.

1669163571202.png
 
TJ4Jim said:
This one drove me nuts until realizing the balancer had spun internally due to the degraded rubber bond, lines show actual spun TDC mark.

View attachment 378803
Click to expand...

Those will throw you for a loop! Maybe the rubber life is 15-20 years. I was in the automotive business for many years and other than 1 vehicle that had balancers failing I can count on my fingers the number of balancers I have replaced.
 
BlueC said:
Interesting. Are these old factory units or aftermarket replacement units that are failing? Any obvious reason for the failures?
Click to expand...

What I would be concern with these days are if the "new" torsional dampers are built with Chi-com rubber.
So many " new " parts are very questionable in my opinion.
 
  • Like
Reactions: BlueC
In the middle east we replaced a number of them. The rubber deteriorates due to age and heat most likely. It is a very simple job. Install new crank seal, timing gears, and chain at the same time because you are already there and it is the right thing to do. I like overkill, consider water pump, belt, belt tensioner, idler, and fan clutch while you are there. It is personally satisfying to refresh all the real estate in the area which leads to longer lasting erections. Mechanical viagra.
 
  • Like
Reactions: macleanflood and Lou
Top Bottom
Back