Dealing With Rusted Weld Bolts on Underside of Cab

The small bolts that hold things on the underside of the cab such as heat shields, cable and tubing mounts, etc. are badly rusted on my truck and any attempt to remove them is pretty much guaranteed to break off the entire bolt. Wondering about how others have approached removal when that's necessary, and if there are any options for replacement once this happens.

I tried a few search terms and came up with some threads about the catalytic converter bolts, but not these puppies. I recall a message thread a while back where someone mentioned using heat was a bad idea because it can start a fire in the cab if it gets hot enough. Penetrating oil alone hasn't worked (tried this on one for the exhaust heat shield that was mostly fallen off anyway... see below). Considering whether a nut splitter might get the nut off without damaging the threads. I've seen 'em but never used one, but looking at the nut I'm not sure it'll get into the thick part of the flange. Any tips?

 

Soak in. PB Blaster for 24 hours

 

You need a heat inductor

 

As mentioned, heat and a penetrant is your friend such as kroil. Also be sure to use a wire brush and clean up exposed threads of the bolt to prevent the nut from getting hung up on that.

 

I have had good luck with crc freeze off spray, but nothing beats a benzo torch.

 

Is there any concern applying heat to the nut that it can melt the carpet in the cabin, or that it can catch fire, or that you'll get unlucky and a wiring harness runs right where you're applying heat and melts a bit? Pulling the seats/carpet should take care of that issue in any case, I would think.

Can these bolts be replaced, and is welding one in the only option? By my eye these look like they get installed using some special tool like a pinch welder. I suppose a body/frame shop could probably do it? Not anticipating having to do so, but curious how best to deal with an important one should the need arise.

 

I had one of those heat shield bolts peace out while trying to remove a seized nut. I actually just used good old JB Weld to put a new stainless bolt back in the divot that the old one had been spot welded into - these aren't a high stress part, they just hold the heat shields on.

 

Was just about to create a thread on some broken bolts I have to deal with as well... After my alignment something sounded off so looked under and noticed my skid plate was only held up by one bolt! All three others were broken off... Managed to unscrew one but the two closer to the front are completely rusted in... I put WD40 on them the past couple of days but that hasn't worked.

So heating them up may do the trick? Aside from that, what else can I do? Drill them out?

 

Heat & PB Blaster.

I ended up snapping those on my truck and replaced them with some U clip nuts from the local hardware store.

 

"Break Away" is another more aggressive penetrating fluid you can try that I have heard works good. My mechanic recommended it but warned that it works
in part by attacking the rust (dissolving it) and advised me to stay away from brake lines and their mounting hardware, because it will eat right through them if they are bad enough.

 

There may be enough of the bolt left to get vice grips on them and get mid-evil.

 

I saw a vid or a youtuber restoring rusted out pistols and rifles by soaking the metal in this juice.