Engine/Transmission (1994 - 1998) Harmonic Balancers..... Do they ever wear out?

[Dennis Garrett]

After I put in the GSK, the 215's, the lever adjustment, TST kit, & some other stuff (See signature), I was left with a good running truck with a rough idle. Now I'm getting a faint irregular, hollow, rumbling, ringing noise most cannot hear, but I spend a lot of time in my truck and I know how it normally sounds. I crawled around under it today while idling, and it seems to be coming from the oil pan. If I fold up a shop towel, and press it up to the pan with the palm of my hand, it absorbs the sound, and I can't hear it. While looking around, I noticed a little belt slap while idling, and wondered if what I'm hearing are early signs of Harmonic balancer problems. Could vibration be travelling back through the crankshaft to vibrate the pan? I read in an old TDR about a guy who put a bigger balancer on his truck after some HP upgrades. Is it time? I have 165K, and 300Hp at the wheels. What happend to these when they wear out, how do you check them?

 

[M Barnett]

Yes, they do wear out. You might want to check with Cummins about the 5. 9 . I recently was going to replace the one on my N-14 until I found out it was $1,000 plus labor. The big trucks, I believe Cummins recommends replacing as at a certain mileage. I have never heard of one going bad on a 5. 9 . If its bad, the engine will shake, vibrate.

Michael

 

[drees1]

Checking the Balancer

Dampers, 101:



There are 2 types of harmonic balancers in wide use today. The rubber style, and the viscous fluid style. Ours is the rubber style. You can tell by the layer of rubber between the inner hub and the outer ring.



It is easy to check. First examine it while the engine is idling using a bright light. You are looking for wobble in the outer ring. Most run pretty true. A slight wobble, barely detectable, is ok.



Next, with the engine off, or the balancer removed, inspect around the rubber joint. Make sure the rubber is flush with the surface and not extruding out or un even. The rubber is in a lot of compression when the outer ring is installed. If the rubber starts extruding outward, it will expand to it's original size and work it's way out. That is not good. You can also inspect the rubber edge for weather checking or cracks, but unless a piece is missing, it will be ok.



If the rubber balancer inspects ok it is probably fine. The only other thing that can go wrong is that the outer ring can slip rotationally on the hub. But usually when that happens, you have wobble or rubber coming out. It should last a long time.



The viscous damper is the other style and it looks like a solid piece of metal. Just inside the outer case is a ring of steel that fits very close to the case (within thousandths of an inch) the case is full of fluid. As the crank oscillates the fluid creates drag between the case and the ring. If a viscous damper is leaking or has a mark or dent in it it is bad. Otherwise it is ok.



The purpose of the damper is to cushion shock on the crankshaft every time there is a combustion bang on the piston. We have all heard of stories of a crankshaft breaking if it is dropped on the floor. Well, the power pulses from combustion are pretty strong and regular, so they create a ringing effect on the crank. The damper resists these twisting vibrations to protect the crank.



Our damper does nothing to effect the balance of the engine, but some dampers are intentionally out of balance to offset an internal out of balance.



As the ring oscillates on the hub some heat is generated and the damper may run warm or hot. You only need to improve the damper if it is running too hot. Then you need a better damper matched to the new condition.



Doug ReesOo.

 

[rrausch]

This type of lucid response, full of information, is one of the reasons I became a member of this group. Thank you drees1, wherever you are!

 

[Dennis Garrett]

Thanks Doug, that's more than I ever heard about these things, & I'll look at it more carefully next time I get home, now that I know what I'm looking at. I might stop off at Cummins in KC, and ask them about it too. They might be able to look at it, or figure out if that's where the noise comes from. It's annoying to me, but the wife can't hear it. It's kind of a very slight back ground noise I've heard for a couple of weeks, checked everything else already.

 

[illflem]

Three or four winters ago the WA state Hwy Dept started using a "new improved road ice melter guaranteed not to damage vehicles". Their assurances proved to be very wrong. The stuff melted ice great and was easy on metal surfaces but ate electrical insulation, rubber brake lines and harmonic balancers. My buddy who worked for Cummins NW said their shop was full of them, the rubber was coming off in chunks...

 

[baby.driver]

Thanks for the education Doug.



Jay

 

[CumminsPower98]

Replaced a harmonic balancer on a Chevy 454 a few weeks ago that was in real bad shape. The outer ring and rubber were half way off (up against the main pulley) and the engine vibrated pretty bad. It ran smooth after installing the new unit. If something like this goes on too long, the crank shaft can be damaged or break.

 

[C Schomer]

M Barnett, the viscous balancers can leak so slowly you don't see it. Then one day... BANG, broken crank. The funny thing is, Cummins has some much less expensive balancers that look the same but for different applications. I've used a balancer for a stationary NTC on my OTR truck NTC. It was about 1/3 the cost. The parts guys didn't know what the difference was and I never had a problem with it. I became a believer in replacing the balancer when they recommend after I had to pull my engine and put a crank in it. The front end of the crank broke off with the balancer and tore up a new oversized radiator and fan that I just put in besides. That was about a $3k (parts only) bang that time and a week of downtime! Craig

 

[Deezul1]

Doug

Thanks for an excellent description.

 

[M Barnett]

C Schomer: Ouch, that would hurt. I have been lucky I guess and never had one go bad. I knew that they cost 3 - 4 hundred dollars and it blew me away when they wanted $1,000. Is it O-K to use one for a stationary motor? I wonder why the difference?

Michael

 

[Dennis Garrett]

I dug out that old TDR that had the article about replacing the balancer. It's issue #18, fall of 1997. The article was written by Scott Daiglesh. The P/N for the bigger damper is Cummins 3924435. It's larger in diameter, and it only required that the Tachometer sensor be re-adjusted to compensate for the larger diameter. He says these are a good addition to cope with the additional strain on the crankshaft when engine's output is increased. It's more able to absorb the inpulses & torque delivered by higher HP. Might be a good idea, but I think the noise mine is making is coming from the suction tube rattling against the inside or bottom of the pan. Guess my next adventure will be to pull the pan & see why that's happening.

 

[HEMI®Dart]

Thanks for the great post Doug!



Dennis,



You already have the big balancer. I thought my 175 HP engine had the little one too. Nope. It's the 215 HP balancer. I think the only trucks that got the small balancer was early the 160 HP Auto trucks.



I looked till I was Blue-in-the-face for a nice aftermarket viscous type balancer for our engines. They don't make them. A guy even was going to check on the interchaneabilty of the Diamond B 370 HP marine engine's damper. It wouldn't fit either.

 

[HEMI®Dart]

Check it just in case

The big balancer or 215 damper measures about 9½" across. (OD)

 

[C Schomer]

Michael, I know one of the shop foremans at Cummins RM. He was in a field service truck working on stationary engines for 20+ years. He's on vacation for a week but I'll check with him when he's back. Craig

 

[csevers]

they do go bad

We just replaced one at work on a freightliner fl60 it was 1/4 inch off from the out side ring to the inside the driver never said a thing about it truck shook like crazy. Go figure?

 

[Hammer]

doug...

nice job helping to explain the dampeners to the gang. .



Craig...

I gotta tell ya,in my years of racing,both dirt and drag,I've used some of the best dampeners made,both rubber(i. e. -ATI super Dampener)and viscous(i. e. -Fluiddamper)and never had a viscous one leak,,I had a ATI twist apart at 9900 at Lincoln one night when my driver jumped the cushion and the sprintcar jumped out of gear and went into orbit,,I've used fliuddamper for years in my 440/6 superstocker and my buddies 2 SS/AA Hemi cars with no failure yet,,The 440;s never got twisted into orbit like we do our hemis and they have seen 8200-8900 in the traps at speed without failure,,The are right,no one as of yet,keyword yet,has made us a upgraded dampener,but one never knows what may pop up when you least expect it..... Andy