I wanted to get some responses for the following situation:

I had my vehicle serviced on or about 16 March 2009 at a Mitsubishi Service Center in PA. At that time, it had approximately 101,000 miles with no major mechanical issues. I originally purchased the vehicle in the spring of 2004 and at that time, it had approximately 73,000 on it. Having driven the vehicle almost 30,000 miles with no mechanical issues, I felt it prudent to receive a timing belt and water pump replacement service just prior to embarking on a cross-country road trip to prevent any potential problems or damage to my vehicle. At approximately 103,000 miles, only 2,000 miles since receiving the timing belt service at Mitsubishi dealer, the check engine light illuminated on my dash. Not noticing any serious mechanical malfunctions at that time, I proceeded to drive to Arizona to avoid delaying a pre-planned road trip involving several family members.

I arrived in Arizona with approximately 106,500 (mid July 2009) on my vehicle, when I had the check engine code read with a scanner. The code read cylinder number five was misfiring. I checked under the hood to check the ignition cables and noticed one of the electrical connectors on the coil packs was not snapped into place. I snapped it into place and cleared the computer code, which resulted in no warning lights until the following month. In mid-August, the check engine light illuminated again indicating a random misfiring code. At this time, I also noticed a very consistent but unfamiliar metallic noise coming from the engine belt area. From my past 30,000 plus miles, I never heard this noise before. Not wanting to cause any further damage to the engine, I used an alternate vehicle for my transportation to Fort Benning, GA while on military orders for approximately two months.

I returned to Fort Huachuca, AZ late October 2009 and recovered the vehicle from storage. I drove the vehicle to a Mitsubishi service center in AZ to receive diagnoses and repair of the not forgotten engine trouble. At this time, the vehicle had approximately 107,500 miles (31 October 2009) only 6,000 miles (seven months) after the service performed at the dealer in Pennsylvania. I was informed by the certified Mitsubishi service center in AZ that the harmonic balancer was not functioning properly. I was also informed that the harmonic balancer maintains proper engine timing, lubrication, and crankshaft balancing to promote engine longevity and performance. I had the service center replace the harmonic balancer in hopes of rectifying the problem. Even after a new harmonic balancer was installed, the check engine light continued to illuminate indicating abnormal engine vibrations and improper cylinder firing.

At that point, the technician advised me that the improper function of the harmonic balancer over the previous extended period of time resulted in undue stress and vibrations that caused premature wear of the crankshaft bearings. The next step to fully repair my vehicle would require replacement of my entire engine block resulting in a very costly repair ($6,300).

Keeping in mind the original fault causing this sequence of events began at approximately 103,500 miles and the diagnoses was identified within MitsubishiÆs service warranty (12 Month, 12,000 miles) I feel this situation is not a coincidence. I would like to reiterate the 30,000 miles I drove with flawless engine performance and the fact that my engine has completely destroyed its bearings only 6,000 miles after service. Additionally, I would like to point out that the harmonic balancer must be removed in order to replace the timing belt.


Currently, the dealership takes no responsibility in this matter. I would like to get some professional responses to the following two questions:
Do harmonic balancers ever go bad with normal wear and tear or would improper function of a harmonic balancer be a result of improper removal/installation?
Hypothetically, if I were to purposely install a bad harmonic balancer on a perfectly good engine, how long would it take for the abnormal vibrations to wear out the crankshaft bearings? (1,000 miles, 5,000 miles, 10,000 miles, etc)
Mark

I hear your pain but theory seems a bit far fetched. There are no balancers in your engine. You have SOHC V6, balance shafts are only somewhat needed on 4 cyl engines. Even then you can just take the off fairly safely.
Actually I'm not quite sure what you have had replaced unless we are talking about automatic belt tensioner. Which doesn't have to be but good idea to replace when replacing timing belt.

Did anyone actually took engine apart to look at bottom end? Without inspecting the bearings death sentence to engine is a bit premature.

Sounds to me that dealership just trying to get you to go away.

1. How do worn bearings cause a cylinder to misfire? (Not meant rhetorically. I don't know myself if it is possible.)

2. My balancer started to go via slipping. The outer puller was seperating from the innner "hub." Even so, this only affects the accessory belts.

3. The timing itself is determined by the crank gear behind the balancer, on the end of the crank itself.

4. How did he diagnose the worn bearings?

5. I don't know what the HB does for lubrication...???

6. Does it still make the metallic noise?

7. I wonder if the misconnected plug wire caused some grounding out and if that coil pack is then problematic?


So, no real answers from my pea brain. But I would say that it all smells like dead fish to me...

i agree with alex on this one. you dont have a balancer....though you do have a damper. these are known to fail after time.


now regarding the main and rod bearings.....a bad damper will cause these to fail but once a new damper is installed unless you actually spun a bearing (making a knocking noise) you wont have any issues. these engines are already known for having bearing issues so this is why i think the shop is jumping to that conclusion (if its not making any noise at this time)

there are many things that could be causing the random miss. loose or mispositioned timing wheel (the part that the sensor reads), ignition faults, fuel system faults, etc.


considering someone was just in there doing a belt it IS possible that the issue lies in that area.


regarding damaging the pulley to remove it....it is possible but considering you went 7k miles its not likely it was damaged during removal. 99% of the time the crank pulley will come off with just a little wiggling. being in PA it could have been rusted on. unless the tech that did the job was fresh out of school and that was his first timing belt job on a 6G he would have known how to properly remove it.


keep in mind in the 3000gt world many ppl install un-dapened pulleys with no ill effects even after 30-40k. (Personally i never will.)

Sounds like a lot of BS to Me. The "harmonic ballancer" he's referring to is actually the crankshaft pulley as refered to in the Mitsu FSM. And no this pulley does not go bad under normal circumstances. Its pretty much a solid piece of steel with a bit of rubber to dampen vibrations a bit. Have you examined the pully? If it was bad you would be able to tell by looking at it fairly easily by looking for chips in the pully surface or cracks or chunks missing out of the rubber portion (not likely)

What makes the technician (I use the word lightly here) believe that your crankshaft bearings are bad? Do you have a knock in the bottom end?

"I was also informed that the harmonic balancer maintains proper engine timing, lubrication, and crankshaft balancing to promote engine longevity and performance."

Also this statement is almost totally false. Yes the pully helps balancing somewhat, but mostly it "dampens" vibrations from the accessory drive belts which is its primary purpose (to drive the acesorry belts like the power steering belt and the fan belt)

It has nothing to do with timing of the engine, other than the mark on the side to read your timing light off of. Also the pully has nothing to do with lubrication of the engine. It's on the outside of the engine for crying out loud....

Sounds to me like you have a simple misfire. Perhaps a fouled plug or bad coil pack or wire. If you had bad crank berings you would probably know by the heinous sound of knocking combined with a loss of oil pressure....I say this guys trying to take you to the cleaners. Get another opinion and check out your pullly and post pics of it here and we'll let you know if its bad.

I agree with the other guys, but i'll add give it the Italian tune up that always makes the DOHC quiet down <img src="/forums/images/graemlins/lol.gif" alt="" />.

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If your running at a resonate frequency of the system with a bad damper you can damage the main bearings. The higher degree of vibration will increase spark scatter and could thow a misfire code.

If you had a bad damper and a non firing plug that would result in a much larger impulse variation. If that happens at resonant speed of the crankshaft it could generate very high loads on the damper and the mains.

A failed damper can damage your mains bearings. A misfiring plug increases the loading on the damper and can shorten its life.

The hard part would be showing cause and effect of a disconencted plug to a failed damper. The damper may have been failing all on its own.

There is no clear answer on the effect of a bad damper, it will depend on the rpm that the motor was run at, oil film thickness and the loading. If you never hit the resonant frequency it wont matter. If you have a bad damper and your at the resonant frequency it could be a matter of seconds for a crank to break and or start damaging your mains.

Good read:

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1: Yes the ballancer can fail over time, the rubber can get hard, slip or lose it properties.

2: Too many variables to be able to provide an answer.

Kevin

Ah, so if the firing isn't on, then if delayed or weak, there won't be sufficient cumbustion force to push the piston as intended, thus putting abnormal forces on the rest of the crank assembly, starting with the bearings...?

As for the HB, I was thinking about how the one I have has shallow drill impressions, like you'd have if it was balanced. Didn't know the part about the resonance.

Good stuff, as always!

Definitely a good read but I still think mechanic put a little too much function to such a device.

Seems like it does almost everything under the moon but yet it's just there plus I'm not sure how can you replace something that doesn't exist by itself. It's part of the crank pulley. How does it not function? I mean I can fell apart. I mean it like saying my wheel waits stopped functioning when they just fell off and the wheel is off balance. It's true but rather cryptic.
Did he replace a pulley? (#40)
I understand that such failure is theoretically possible but I'd bet pretty improbable on non-racing real-life usage engine. I'm starting to forget (been many moons since I replaced my timing belt) but I think 3.0 V6 doesn't have one but lives on happy long life.

The damper fails by slipping on the hub or the elastomeric hardens so its function is reduced.

The damper and the hub are one piece. What matters is if you are at the harmonic frequency of the crank or not. That depends on the rigitity of the crank and the pulse frequancy of the cylinders firing.

With a bad damper all you need to do is hold the RPM at the harmonic frequancy to cause damage. The harmonic occurs within the normal operating RPM of the motor, if it didnt the factory would not have put a damper on. Once your above ( below) the criticle frequency you dont need the damper.

So a high RPM V6 that is racing probably wont have this problem.
Just go past the bad RPM fast enough and you wont have a problem! No I did not make that up, it was a trick that was used in tehh 60's to get inline sixes work as race motors in boats. Once past that RPM the motor worked just fine at 7000 RPM.


Also since all elastomeric dampers age and lose efficancy every older V6 could have this issue.

This easily could contribute the the crank bolt failures we have seen since the connection to the crank will see a much greater stress with a poorly operating damper.



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Add that to a crank thats been re ground that removed the factroy rolled fillets and you might be able to explain a lot of broken engines.

Kevin