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Hi new to the forum! I bought a 02 GMC sierra z71 extended cab about 3 yrs ago. I looked the truck over and it was spotless then all of a sudden after this brutal winter we had (from Ohio in the rust belt) little bubbles appeared in the passenger rocker panel just at the very back. I know these trucks are known for rusting in these areas but when I got under the truck not a spec of rust .... I am assuming it's rusting inside out. has anyone else had this issue and what can be done to stop the rust if I cant find the source of it? truck only has 80k on it so would hate to let it just rust away . any advice would be appreciated.


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Mine are bubbling in a few places... I intend on stripping paint off my rockers in a few months, cutting and patching any rust through, ... chip guarding and painting the rockers, then spraying oil/fluid film inside them to stop and prevent further rusting.

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We just did a job like this too. A 97 sierra 1500 reg cab. Took the bed off, cut off the rust on cab corners and replaced the metal. Fixed door rust too on bottom inside. Took doors off cut rust out, sanded, put new metal in, bondo, and bedlined below molding

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Anyone with an older vehicle should have the car/truck treated annually.




Fluid Film


Oil undercoating.


Done by a professional shop that specializes in this treatment.


I live in snow/road salt country.


My 18 year old car has zero rust. Treated every year.

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The body on my 03 Silverado is still pretty much rust free. My concern is the frame area towards the rear. I already replaced brake lines and leaf spring shackles due to rust. Other then using the Por 15 stuff is there anything else i can spray on there to slow the rust down? I was thinking of just scrapping the rusted areas and undercoating. Any ideas and suggestions greatly appreciated !


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  • 1 month later...
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The factory wax does more to help rust the frame than it does to prevent it. The wax is already peeling off any edges on the frame by the time it's delivered to the dealer. Water and salt seep under the cheap wax, which then goes to work on the steel. This is why we're seeing trucks on the lot with rust bubbling up under the wax. Honestly I'd prefer it if GM would leave the frame bare or just lightly oiled so I could give it a proper coat of POR-15.

Edited by HondaHawkGT
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