2008 Uplander Multiple Issues - Vibration and Noise - Front End

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  #1  
Old 05-19-15, 05:54 AM
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2008 Uplander Multiple Issues - Vibration and Noise - Front End

Hi,

I've been experiencing some nagging issues with this 2008 Chev Uplander with just over 50,000 miles on it, for some time. Last year, it pulsed and vibrated while braking hard, almost scary at highway speeds. It also clunks usually when starting out from a stop, but not usually when turning or going over bumps, occasionally lately it started doing this clunking thing also when slowing.

Last year I replaced the rotors and pads all around with Raybestos premium ceramic pads and top of the line rotors. I also replaced the rear calipers as I could not squeeze them with the special turn and push tool. The pulsing and vibration disappeared and the van was braking beautifully. The clunking was still there, though.

Now the vibration is back but it has no pulsing, leading me to think that the vibration is suspension related. The other day I jacked up the vehicle and supported it on two jack stands to try to nip the problem in the bud. I tapped on all sorts of parts to see if anything sounded strange and grappled at various components to see if anything was loose. All I could find was a tinny sound coming from the lower joint on the left anti sway bar end link. All four joints on the end links were low on grease and sealed, so I ordered a pair of very nice Moog units with grease nipples to replaced the old ones. That done, both problems persist.

While I had the vehicle front end up in the air with the wheels off, I looked at the brakes to see if they were OK. The rotors looked good on inspection, the pads also looked good with even wear (very little). I loosened the calipers with the intention of squeezing the pistons a bit to test them, but only loosened them because the rivets on the inner pads make it nearly impossible to slide the circular ends of the pistons on the calipers of this vehicle off the pads, so I am not sure if the front caliper pistons are working well, or if they are the cause of the vibration by sticking a bit. The brake sliders were clean and lubed also.

I am wondering what could be causing both the vibration and clunking noise. Could they be related?

Any and all suggestions will be appreciated.

quickcurrent
 
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  #2  
Old 05-19-15, 06:01 AM
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A pulsating vibration during braking is often warped rotors. Not surprised that new ones fixed that portion. Have you checked the driveshaft for worn U-joints? Also tapping parts doesn't tell much, you need to have the front end off the ground and move the tires looking for play in the suspension and steering parts.
 
  #3  
Old 05-19-15, 08:16 AM
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Right marksr, I knew the pulsating feel would be fixed by the new rotors, the only reason I replaced them, because the old ones were not yet worn out, but obviously warped.

I've tried moving the wheels around and all seemed good. Some sealed joints don't seem to have a whole lot of grease in the boots, but that alone is no reason to start replacing parts.

I'll have to have a look at the drive shaft. Not sure what joints there are, likely one U-joint and CV joints, but I did not hear any sounds that would resemble U-joint noises, I know those fairly well. CV joints are pricy, yikes, but I did not see any lube leaking from anything the last time I looked around. There is only one way to check U-joints I know of and that is to take the axle apart and move the axle parts about the joint, not sure if it's worth doing that unless I heard a metal scraping sound. These are clunking sounds I hear and not as the vehicle moves, just briefly when it's starting to move, once it's rolling it handles very well, until I apply the brakes hard.

I also recreated a brief clunking noise when I was jacking up the vehicle on the front driver's side! Strut bearings/bushings???

I cannot recreate the clunking noises by bouncing the vehicle!
 
  #4  
Old 05-19-15, 12:58 PM
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The clunking noise may only be present when pressure is removed from the suspension. This occured when you jacked up the vehicle and might also occur when hitting a bump and momentarily being airborn before regaining contact with the road. Bouncing the vehicle may not allow it to sufficiently separate.

- Peter
 
  #5  
Old 05-19-15, 04:07 PM
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Are your sway bar end links solid?
I have an 07 Uplander and have replaced both end links at 80k miles.
 
  #6  
Old 05-20-15, 07:45 AM
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I have replaced the OEM anti sway bar links with Moog ones. The Moog ones are much more heavy duty than the OEM ones, and equipped with grease nipples at each end, 2granddaughters.

The clunking noises don't usually happen when hitting bumps, pjaffe, but when starting to move from a stop. Lately they have been happening more frequently, including when slowing down!
 
  #7  
Old 05-20-15, 07:48 AM
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I think I have found the cause of the vibration, I heard some scraping of the brakes yesterday - the caliper on the left may be seized, possibly the one on the right also, I am going to struggle with those calipers today. Not quite sure how I am going to get the pistons to clear the rivets, especially if they are stuck, without damaging the pads.

Still have no clue on the clunking noises - those are a bigger mystery!
 
  #8  
Old 05-27-15, 07:45 AM
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Front caliper pistons squeezed smoothly, waiting on the return of a lend-a-tool caliper tool so I can borrow it to check the back calipers as they are the turn and squeeze type.

If anyone has any ideas at all on the clunking noises, don't be shy.

Thanks
 
  #9  
Old 06-17-15, 07:25 PM
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For anyone with similar problems to mine, I have managed to fix both.

The clunking noises were caused by six bolts that weren't sufficiently tight - three on each steel brace running from the top of the struts to the front frame of the vehicle. I tightened each up to about one full turn with a socket wrench - problem solved.

The vibration was caused by the driver's side front rotor - it was badly pitted and rusted on the inside surface after just 7,000 miles - so much for Raybestos premium rotors! The steel was full of inclusions of rust and dirt from the manufacturing process and hunks of steel simply pitted off. They were made in China, so I suspect that they were made from recycled steel. I have again put on the same rotors but with a coating that is supposed to help the rotors last longer. The coating will likely do diddly squat if these also have inclusions. If these don't last several years and outlast the pads on the vehicle now, I will never buy another Raybestos rotor again.

Hope this helps somebody.

Cheers
 
  #10  
Old 06-18-15, 02:17 AM
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AS much brake problems as you are having , I am wondering , are you hauling a lot of weight ? Or do you have very aggressive braking style ?

God bless
Wyr
 
  #11  
Old 06-18-15, 10:43 AM
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A pulsing in the brake pedal is from thickness variation in the rotors not warped rotors. If a rotor is warped it will move the caliper back and forth in its mount but that doesn't feed back to the pedal. Thickness variation comes over time from runout that is induced in the rotor. Runout happens from dirt or rust between rotor and hub, incorrect wheel nut torque and stuck calipers. Chevrolet/GM has a detailed TSB addressing brake vibration that discusses your issue in detail.
 
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