Hey Guys,

I have a 2001 Expy with the 4.6 V8. She's got about 72K miles on her. Truck is great except for one thing - while idling (after the vehicle has had a chance to warm up) and at various RPM's while in park, the truck shakes or vibrates. A buddy of mine suggested that the harmonic balancer may have gone bad. So my questions are this:

-Does this engine have a harmonic balancer?
-If so, what is it's purpose?
-Is it common for the harmonic balancers to fail?
-If/when they do fail, what are the symptoms?

Any help is appreciated!

Regards,

Anthony

 

Harmonic Balancers can go bad, but its not very often. I had one go bad on my 97 F150 4.6 Let me tell you its a huge difference when it was replaced. I would definetly look into it, but consider other possibilities of problems first.

 

it has a harmonic balancer

the purpose is to prevent the drive shaft from breaking, it accomplishes this by keeping preventing excess twist of the crank. when a cylinger fires the portion of the crank that is in front of the firing cylinder wants to twist because it is not being driven. the balancer has an inertia ring ( A MINI FLYWHEEL) which dampens or reduces the twist. the correct name is torsional damper.

it is not common failure

when they fail there are several symptoms depending on severity of failure.
the majority of the failures are nearly undetectable. the inertia ring will rotate about the damper hub. the only noticable issue is that if the evhicle is a precomputer vehicle the timing mark will be misaligned.

severe misalignment is when the inertia ring slips on the hub and becomes ****ed on the hub. the engine will shake really bad like it is missing on 3 or more plugs.this is easy to detect. jack up the truck and observe the damper with the engine running, any misalignment will be easily visible.

you problem does not sound like a torsional damper

 

Check your engine oil level. I have found several at VO plants with severe vibration that were 3-4 quarts over fill. Just a long shot but a few quarts over in these engines can generate a pretty good vibration. Good luck

 

Oil is within range so I doubt that this is what's causing it.

If it's not the harmonic balancer, I'm not sure what else to check. Plugs and coils are new. I have no CEL on. IAC is new. I've tried a replacement set of injectors as a test and that wasn't it. Is it possible that maybe the motor mounts have failed?? Is it common on these trucks? I've tried power braking the truck to see if the engine moves upward but everything looks ok. This one really has me at my wits end. Any other suggestions are much appreciated.

Anthony

 

Run your truck until the vibration starts. Shut the truck off and remove the serpentine belt. Restart and see if vibration is still there. The vibration may be caused by the A/C, P/S, ALT, Water pump, fan or a pulley. It could be a failed Damper I have seen a few. Look for rubber breaking away around the damper face. There is a rubber core ( for lack of a better discription)that can come apart and throw it out of balance. Easy to change with a puller if it is defective. Possibly a torque converter? Hard to guess at what the vibration is caused from. Good luck.

 

I got a similar problem on my uncle's 99 Grand Marquis, 4.6 Romeo. It looks as though the rubber sandwiched in the middle of the dampener is coming off and is vibrating. Only thing is the engine doesn't budge, it's just to look at it that you notice it. The godamn tensioner pulley and/or idler pulley noise drew me to this.

 

A bad damper should show up at all engine temperatures, not just after the engine is warmed up. I would take a hard look at your radiator cooling fan (assuming it is a mechanical fan with the temperature sensitive clutch). Removing the serpentine belt, as suggested above, will also work for testing the fan. A belt tensioner that is starting to freeze up can also cause this type of problem - every time the A/C compressor comes on, or the alternator high charge kicks in, the tensioner will start jumping and cause you to feel the vibration. Again, the serpentine belt removal test is a good start.

 

Was doing a search on serpentine belts, and saw this thread, I know I'm late to the party, but thought I'd share an experience I'd rather forget...

Regarding the Harmonic Balancer:

I had one fall off (yes, it fell off) on the freeway one time. Lost power to everything, coasted to a stop in the median. Got a tow to another shop altogether. I had recently had the engine rebuilt, the nimrods re-used many a nut and bolt, hence, why I chose to go somewhere else for the repair of the balancer.

Here-in lies the problem: - the guys doing the rebuild had removed the harmonic balancer, but failed to realize that the bolt which fastens it to the shaft is a Torque-to-Yield bolt, which, once is installed at the proper torque rating, is good to go.

If you "RE-USE" the same bolt, it loses it's Torque-to-Yield rating. The bolt had sheared off inside the shaft, and the subsequent repair shop had a way to extract the remnants in the shaft, in order to put in a new Torque to Yield bolt.

Just thought I'd pass this along...

 

Hey guys..another balancer ? my 4.2l does not shake but the balancer moves in and out about 3/8 to 1/2 inch. Could it just be a bad balancer? also I've checked about a new one and i found two types... one 150 and the other 30.. how do i know which one is right?

 

This is the V-8 forum, not the V-6 forum!

 

sorry didn't mean to rub you v8 guys the wrong way..just asking for help

 

You didn't rub anyone the wrong way - you will get PROPER help in the correct forum instead of bringing back a dead thread in the incorrect forum.