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Discussion Starter #1
If there is a thread that addresses this subject, I was not able to find it. So is there any solution to the screw holes cracking out on the front fender wells? When the dealership replaced the fender that they crunched, there was not enough meat left in the original wells to attach so, I let them install one of my spares. Six weeks and 1500 miles later, two of the screw holes are already cracked on a brand new Wheelwell. I recall reading that someone had theres replaced under warranty which I plan on pursuing, my car has major guard and besides this is a new GM part installed by GM people. At the time this replacement was done, I ask them to check and see if there were any service bulletins about these breaking, I thought someone had indicated that they came out with better mounting hardware to solve this issue. Dealership said they found nothing, but it is a problem as I see it. My 2008 NA was cracked when I bought it with only 1600 miles on it and later when I traded it for an 09 GXP with only 3000 miles on it, the wells were cracked on it too. An owner is going to have $120 plus every time the wells are replaced, there has to be a way to get a longer life out of them
 

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I remembered there being something also. Did "search" for fender and it came up with pictures and what appears to be a bulletin, but no number. Lower bolts being replace with push pins which allow for movement.
 

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I too am on my third,maybe fourth set but when the dealer last installed a set on the car he installed pushpins. Not just where they state to install them in the TSB but all around. Been there about a year and no cracked liners yet.

With the way mine are installed there are 2 screws in each liner, that's all. Seems to have worked, so far anyway...
 

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There is a ton of info about this. The inner fenders started cracking back in 06. The factory changed their attachments in 07. Basically they all crack. Using large washers to spread the load and don't over tighten.
 

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Quick question (because I can't look but going from memory because my Sol's in the shop getting the cat replaced.) - the wheel liners are indeed "formed" to shape, right? We're talking the "bubble" shaped liners?

I'm assuming the holes (again, because I can't look - not that I'm missing the car or anything, just 'cause it's been at the shop for two days...) are around the perimeter of theliners?
 

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Discussion Starter #8
Yes the cracks appear at the mounting holes, and they continually crack to the point that peices of plastic will fall out. The fender wells are formed but are very pliable. When crate engine depot shipped these to me, they were able to roll them up so they would fit in the box with other parts.
 

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How much is a new set mine got a little scuffed up and I wanna replace them
 

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I'd ask them not to do that for future shipments. I throw out my 2 cents and see if they can help anyone.

I believe there is at least 2 of 3 things going on here if not all 3. Fortunately the same suggestions will help all 3 possible conditions.

If the liners are injection molded, which I believe they are, the process results in "knit lines" where the plastic has to flow around a pin in the mold which forms the mounting hole. The plastic must flow around this pin and be "knitted" back together on the other side like such:

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These knit lines are inherently a weak point (to varying degrees) in an injection molded product. Gas can trap between the melt fronts, mold release agents can trap there also, the plastic pressure is usually greatly reduced (thereby not forcing the two melt fronts back together very well) and a few other things that can happen. What's worse is that we generally need to hold things down at the edges, so the knit lines also are occurring where the material is thinnest! You may even be able to see a dull line or "smoky" surface between the holes and the outside edges. (Rarely in a straight line as I sketched above.)

If the liners are thermoformed, which they could also very well be, the holes would be drilled in afterward. (Thermoforming tooling is much cheaper than injection molds, so for lower volume vehicles like the Solstice they may have gone this route.) Plastics can be extremely notch sensitive. Stresses from the drilling process combined with sharp edges or any gouging will leave stress "risers" in the material. These are the points where the plastic will begin to propagate cracks from. Once again, we're putting the weak link right the hell where we don't want it - where it's being screwed down!

Lastly, the coefficient of linear thermal expansion (CLTE) of a plastic is magnitudes greater than metals. This means for every degree of temperature change, the plastic will swell or shrink 10, 20 or more times greater than the surrounding steel structure it's mounted to. I suspect the liners are polypropylene or polyethylene. PP has a CLTE of .000096 inches per inch per degree F. So if the fender liner is 36 inches from end to end and the underhood temp goes from 70 to 120 degrees, we get .000096 times 36 (inches) times 50 degrees = .173 inches of growth - almost 3/16 of an inch. If one mounting hole is tight on one side and the opposite end is tight to the other side, well 3/16 of an inch worth of material has to find a place to be.
 

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So, ask Engine Crate not to roll those up. No matter what the process used, they can elevate the stresses already present at the holes.

First I'd recommend that you have clearance all the way around all holes when you install. If you can shift things around so all holes have room on all sides, great. If not, I'd make them bigger. I'd use a hot wire but that's not really practical. Soldering pen would be my next choice. I'd avoid drilling because of stress issues discussed above.

It would make sense that GM went to a push pin instead of a screw. You need something to hold it in place, but let it grow and shrink as necessary. Rob's suggestion of a big washer is great also - but just be sure you don't torque it down too tight. Light torque with some loc-tite perhaps? Spread that load out over a bigger area with a fender washer (ironically enough.)

Whether the holes are molded in or drilled, I'd suggest smoothing the edges out on the holes before installation - even if you melted them on one side to open them up. Just get rid of any sharp edges on the holes.

Hope that helps.
 

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ive also seen a lot of these having issues due to over torquing the bolts down.

personaly i recommend a loose fit and get all your bolts started and then tighting them periodically to spread the stress load.

what i think might help would be to use a larger washer in combination with whats there already.
 

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The initial manufacturing process called for bolts at all holes. This was changed to push pins in the lower holes to allow some movement of the liners. They tend to crack anyway.
 

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Discussion Starter #14 (Edited)
Thank you all for your help. Sly maybe on to something by keeping them a little loose with all pushpins. It seems to fall in line with the wealth of info that chicken wire inlightened us with. Time will tell, I plan on smoothing the holes on a brand new set $57 each @ crate engine ( not rolled up). We will put all push pins in and see if I can get past 6 weeks and 1500 miles without a crack appearing.
 

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Here's another thought. My travel trailer has the "winter package" on it - so it's insulated underneath and has sheets of polypropylene covering it. I lost a chunk of it and my dealer told me they use a self-drilling self-tapping screw with a rubberized washer to hold that stuff in place.

The push pin will give you the movement necessary, but might it allow a rattle or even some flex with wind? The flexing back and forth in the wind would accelerate cracking also. What if you used a rubberized washer (zinc plate or whatever on one side, the underside has a rubber coating) with loctite on the threads? This way you could get enough "squeeze" to hold it in place, but it would swell and contract by sliding under the rubber surface? This would minimize flexing in the wind, eliminate the rattle, but accommodate the temperature changes.
 

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Discussion Starter #17
WOW! That is brilliant. I know the kind of washers you are talking about. They use them for metal roofing material so the screw holes do not leak. A bigger version may be available, that would spread the pressure out.
 

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Discussion Starter #18
Special thanks to Tomato Soup. I spoke my local dealer today about this and now I am getting both wheel wells replaced FULL Warranty! with the push pins. There is no way I could have made that happen, without that service bulletin number you posted. I asked them to check befor they installed. They said there was no bulletin, so when I was able to give them the number later when new cracks appeared they saw the errpr of thier ways. Now they are going to make it right at no charge to me.
 
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