Silverado — Moltenhead Welding

My 2007 silverado started sending gas fumes out of the vents in Autumn 2023. obd2 scan told me there was a leaky evap line.

Looking underneath, I discovered there was also an actual gas leak happening somewhere on top of the gas tank. Scary stuff.

I read through the haynes manual for info about the evap line which confirmed an evap leak would send gas fumes out of the vents in the truck cabin.

Since gas tank was leaky I decided first step was to remove and inspect it. it turned out the leak was coming out of the lock ring, which holds the fuel pump. You can see the rusty lock ring below on top of the pic i took below.

The next issue was the worst of them all. Once I removed the tank, I found one of the crossmembers holding the gas tank was severely rusted out, almost all the way around. Lock ring and evap lines are pretty easy remove and replace jobs once a truck bed is removed. This was not a remove and replace bolt-in job.

With the help of a few buds, I removed the bed from the truck frame and started looking at the damage done by 16 years of northeast winters.

Clearly if I just replaced that cross member, other parts of the frame would most likely sooner than later start looking the same way, so i decided to grind all the rust off and paint the frame.

That tar-looking stuff is a rust inhibitor used by chevy/gmc called Nox Rust X-121B, made by Daubert Chemical Company. It had one job and failed miserably at that one job. I tried using a wire wheel to remove it but it just got smeared around - best way i could figure out was brake cleaner and steel wool.

$15 harbor freight needle scalar did a great job of blasting off first layer of rust and dried up Nox Rust tar chips.

5 days of grinding rust off and i was ready to cut out the crossmember and weld the new one in. it turned out half the cross member was fine, so i cut out the left half of it and cut the crossmember to size.

First weld attached the new crossmember piece to one of the gas tank strap brackets.

Next was the obvious one, welding crossmember in place with a mix of horizontal, vertical and overhead pipe welds.

Next step was paint - I’d decided to use por15. Since I was doing all this work on it I might as well do it the right way. por15 on top of the frame would mean the rear part of the frame would last longer than the rest of the truck. Its tuff stuff. First you apply metal prep solution, then rust preventative coating, then the por15. I had 2 days to finish before autumn temps dropped under the threshold where the por15 wouldn’t set properly so it was do or die time. I won’t go into the psychological details of doing all the above while knowing i had to finish before temps dropped but I’ll leave it to the reader’s imagination.

Next step was loading gas tank back in, along with hooking up fuel and evap lines, the leaky or fucked up looking ones of which I’d ordered replacements for, and all the other minor stuff like electrics. I had a solid friend who came through and helped out with stuff that would’ve been even harder to do solo, he knows who he is and that I appreciate him. He also helped me remove gas tank. This is the video we took of the first start up. That stuff coming out of the exhaust pipe turned out to be either condensation or smoke from gas that had been sitting in tank the last month and a half or some combination of the two. It exhaled clean after driving it around a few days.

Cemetery Fence