Bent Flex Plate (1 Viewer)

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The the vibe AND the smog failure, are you sure a cylinder is not out? As mentioned, why was someone messing with the crank pulley, has someone had the head off and bent a valve? Get a compression check done before you start dropping money on this, too many unanswered questions. Not trying to scare you but have seen plenty of 'it just needs a tune' lines on cars for sale.

regards

Dave
 
If the plate is that bent then it is possible that it may have fractured (or be about to) around the bolt holes, if the rest of the car is good then yes pull the engine or transmission and fit a new plate. Also how does it sound when cranked? Does the starter jam or sound like it is fouling the ring gear? I am still having trouble getting my head around the vibration though?

regards

Dave

Thanks, Dave.
As for the vibration, it's the crank pulley. The best way to describe it is when it's cold at about 1500 rpm, the crank pulley is running straight and smooth. As the engine warms up and idles, the crank pulley is not running straight and smooth. It looks like it's moving away from the engine and back, just a tad. Everything else is normal - starting, etc. I mean, I have seen the bent hole on the flex plate so I guess at high rpm, the affect of the bent hole on the flex plate is minimized. Thanks
 
The crank pulley moving in and out is more likely a harmonic balancer? This is bonded to the crank pulley, the bonding fails and the balancer moves out of sync with the pulley. . This is responsible for dampening engine vibrations. change the pulley and this may cure all the problems, a small distortion in the flex plate is unlikely to cause the vibrations you mention.

As a respectful side note, it is better if you supply all the information in your earlier post it would help with diagnosis.

regards

Dave
 
And you better change the dampener asap before you have to replace the whole crank. I would drive it till then.
 
The crank pulley moving in and out is more likely a harmonic balancer? This is bonded to the crank pulley, the bonding fails and the balancer moves out of sync with the pulley. . This is responsible for dampening engine vibrations. change the pulley and this may cure all the problems, a small distortion in the flex plate is unlikely to cause the vibrations you mention.

As a respectful side note, it is better if you supply all the information in your earlier post it would help with diagnosis.

regards

Dave

Sorry. Yes. I was talking about the harmonic balancer - while the truck is cold, it's running straight and smooth. At idle, it's not running smooth and straight, moving back n forth just a tad as it's spinning around, almost like it's wobbly.
 
And you better change the dampener asap before you have to replace the whole crank. I would drive it till then.

Did you MEAN to say:

I would NOT drive it till then?

Because I would definitely NOT drive it if it has a bad harmonic balancer. Bad things can happen.
 
Agreed about not driving the car, as the motor heats up the rubber bonding will soften and allow the bonding to sheer, if this is the problem then the crank could literally snap! The best way to keep an eye on this particular problem, is to paint a thin line across the entire pulley and balancer with Hammerite or similar paint, if the move out of alignment you have found you vibes. I also agree to giving it a tap toward the engine and pry back out. I am also thinking the PO had a problem and a shade tree mechanic tried to remove the crank pulley or, misguidedly tried to tighten it, hence the damage to flex plate?

regards

Dave
 
I'm thinking that to generate enough force to actually bend the flex plate, the PO had a pry bar in there when retorquing the crankshaft nut, then forgot the bar was in there and hit the starter. That must have been an awful sound.
 
The pulley has a shear pin key way and grove in the crank , left to long (which you have already ) you chance the key way in the crank getting elongated and the only fix is a replacement crank (major job ). If it has a new looking dampener already he has bojanged it already id say . If it was mine i would pull the pulley inspect the key way and replace the dampener if you can see that the rubber is separating. hope it works in your favour. Oh and you will need a big pipe for a snipe to get it loose .
 
The pulley has a shear pin key way and grove in the crank , left to long (which you have already ) you chance the key way in the crank getting elongated and the only fix is a replacement crank (major job ). If it has a new looking dampener already he has bojanged it already id say . If it was mine i would pull the pulley inspect the key way and replace the dampener if you can see that the rubber is separating. hope it works in your favour. Oh and you will need a big pipe for a snipe to get it loose .

I have already replaced the harmonic balancer just to make sure it's good. It is. At this point, the only thing I think is causing the harmonic balancer to wobble back n forth at idle is the bent flex plate. When I removed the old HB, it slid right off, saw the key is ok, installed the new HB into the key, checked to make sure the HB wasn't moving side to side. As I said, everything is good except that when idling, the HB is wobbling back n forth, a tad. I'll post a video. Thanks
 
A bent flex plate will not cause your HB to wobble. Did you replace it with a NEW HB or a used HB? if used, was it a confirmed good one?
 
And is it torqued down correctly? These need a :censor:-ton of torque...

You say it's on right, but do you know that or were you told that? You need a 3/4 inch torque wrench capable of over 300 ft/lbs and a 3/4 inch 30 mm socket to properly torque these down, it is just not going to come out right without the right tools.

I'd still say the harmonic balancer is suspect, and either on loose or became damaged during the install. Can't see any other reason for seeing what you're seeing.

Hope this helps.
 
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Crankshaft movement is controlled by thrust washers inside the engine and placed on either side of one of the crank journals, the CS can (if all is good) move forward and backwards just a couple of thousands of an inch, it would be impossible to detect by eye.

regards

Dave.
 
A bent flex plate will not cause your HB to wobble. Did you replace it with a NEW HB or a used HB? if used, was it a confirmed good one?

To make sure, I replaced the HB with a new one.
 
And is it torqued down correctly? These need a :censor:-ton of torque...

You say it's on right, but do you know that or were you told that? You need a 3/4 inch torque wrench capable of over 300 ft/lbs and a 3/4 inch 30 mm socket to properly torque these down, it is just not going to come out right without the right tools.

I'd still say the harmonic balancer is suspect, and either on loose or became damaged during the install. Can't see any other reason for seeing what you're seeing.

Hope this helps.

I used a torque wrench from Harbors Freight rated at 300 lbs.
 
Finding this very odd, when the engine is cold is there any vibration?

Is it possible the engine is misfiring once the fuel comes out or closed loop, i.e. comes off the 'choke'? This could be described as a vibration.

If you could measure the amount of the damper movement how much would you say it was? Or try and move it when the engine is cols then again when it is hot.

Is it possible you have a bad albeit new HD?

Is it possible there is internal damage to the crankshaft, i.e should there be a thrust washer BEHIND the crank pulley before it is put on?

This would explain movement despite the pulley being tight,

regards

Dave
 
Thrust washer on the crank is the only thing left if the hb is good. Pretty much the only thing that can happen is the pump in the transmission gets punched.
 
Thrust washer on the crank is the only thing left if the hb is good. Pretty much the only thing that can happen is the pump in the transmission gets punched.

That is why I suggested tapping the HB in and then use a pry bar to see if there is play. If there is and the HB is tight then it's a thrust washer issue I think.
 

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