Using impact wrench on rear shock bolts

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LarryJ

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Massachusetts, USA
Hey everyone,

Need to replace rear shocks on my 02 TJ, they're completely off the bushings. Will probably go bar pin eliminators but anyways ...

Splurged on a new Milwaukee m18 fuel impact wrench recently as I've become pretty serious about working on my cars. (Big sale at home Depot right now btw, 250 for the tool and the battery is free)

Whats the general advice for using one? These are very powerful tools and I know these bolts are very likely to shear off and become a nightmare, so in general, is it best to hit bolts full torque / power to start, or should I set it as slow as possible or try a breaker bar first?

PS: I've been soaking it with PB blaster for a week, but don't want to put heat on it due to the proximity of the gas tank.
 
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If you have a propane torch i recommend heating it up very hot first then hit it with the Milwaukee. As you live in rust prone area just be prepared to break them. Sometimes there is not a lot you can do.
 
Just curious, what's the value in doing it by hand?

My understanding is that the impact shocks them loose, and if I start to feel the bolts twist or fail, there's no turning back anyways.

Aside from maybe tightening then loosening by hand to maybe break it loose , wouldnt it be better to go all in with the impact from the start?

Re: propane, it's too close to the tank and lines for my liking.
 
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Assuming you use heat and penetrating oil on rusted fasteners, using your hand on a ratchet you can feel if the nut is turning or not. You get a feel for turning or snapping. If it is not turning, going back and forth can often loosen it up without snapping it off. You work it off. Some fasteners you just have to be resigned to snapping, cutting, drilling and replacing. No hope. Getting a nut cherry red however works wonders. I do most of my own work and don't mind spending the time by using manual tools. I'm an old mechanic who learned the hard way the value of not snapping things off if you don't have to. I do not use a large ratchet on a small bolt. Stripping threads can happen if you weren't paying attention.
 
LarryJ said:
Re: propane, it's too close to the tank and lines for my liking.
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I understand what you're saying there.

I've used both propane and oxyacetylene torches near gas tanks and other stuff over the years but I've always used at least some sheet metal as a shield while paying attention to where my flame was being aimed. Oh yeah, I also always made sure nothing was leaking any type of fuel to begin with.

I'm not saying anybody has to use flame, I'm just saying it's not impossible.
 
I’m one of the unfortunate people who live in the rust belt as well. Southern Indiana.

I soaked mine for a period of about 3-4 weeks. Going out every day, and spraying them with Pb blaster, and working the bolts back, and forth by hand. Then sprayed the tops of them to the best of my ability. Over that month, I got them to break loose where I could get them to back out about 1/16-1/8 inch. I finally got tired of jacking with it. Grabbed my impact, for the hail marry, started working them back and forth. They finally backed all the way out. To my surprise, I didn’t break or strip a single one.

I give the credit to persistence, and probably 1 1/2 cans of Pb blaster. I did not use any heat. I also put an excessive amount of anti-seize on them when I installed the new shocks, to try and avoid this PITA if I ever need to get them back out again.

Good luck with yours! Stay after it!
 
You will spend more time trying not to break them than to break them off, cut the nuts off, and drop bolts in from the top.

It takes 30-45min to cut all 4 out with a dremal and diamond cutoff wheel.
 
billiebob said:
Rear shock bolts are the most likely bolts on the TJ to shear off.....
do them by hand
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X2 - You might use the new impact wrench on the bottom bolts depending on the amount of corrosion on them, but definitely agree with @billiebob about the uppers. Spray the hell out of them with Kroil for a few weeks and then treat 'em gently!
 
whitrzac said:
You will spend more time trying not to break them than to break them off, cut the nuts off, and drop bolts in from the top.

It takes 30-45min to cut all 4 out with a dremal and diamond cutoff wheel.
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How did you get access to cut the nuts off? I broke outer drivers side upper and ended up cutting a hole in the tub to cut the nut off with a Dremel and a cutoff wheel.
 
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Mine broke on both sides. Air chiselled off the nuts and used grade 8 bolts with lock washers. Also did the BPE since I was already that deep into it.
 
Before trying to get those upper bolts out, spray the heck out of them with either Kroil or Liquid Wrench. Or Break-Free if you can't find either of the first two. Don't waste your time using WD-40 or PB-Blaster, neither of those work well.

The upper bolts used to hold the shocks are well known to seize/corrode in place, especially in places that salt the roads as they do in your state. Spray the upper bolts several times over a couple hours, give it time to work. For those particular bolts, I'd be extra-careful removing them since if they snap off you've got a big project ahead of you. I'd also use a ratchet wrench on them, too much chance the impact wrench will shear them off given your salted roads.

P.S. Spray above the sheet metal where the nuts are. You can use a flexible tube to spray up above that area from the side IIRC. Kroil or Liquid Wrench can perform magic/miracles in saving seized hardware from shearing. Make sure to give it time to work!!! A couple days wouldn't be excessive.
 
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I broke the inner passenger side bolt off, and the outer driver's side. Yesterday, I had an opportunity to work on the passenger one. Ended up drilling a hole through the bolt so I could collapse it in on itself a bit, which allowed it to break free. All told, it took almost thee hours to get just one broken bolt out.
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I agree with the Kroil recommendation. I live in the Northeast and everything gets rusted on the TJ. The last few projects that I've taken on I've sprayed the nuts & bolts a week or two before then again several times closer to the project date. This worked really well on my rear control arms, O2 sensors and the front and rear shocks. Next time you order from amazon add it to your cart.
 
Fonz54 said:
How did you get access to cut the nuts off? I broke outer drivers side upper and ended up cutting a hole in the tub to cut the nut off with a Dremel and a cutoff wheel.
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Put the dremel up through the hole where the shock normaly sits.

No need to cut holes in the body.
 
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I'm just going to spray them every night for a week or even two, it's a project car so no need to rush.

I also bought this : https://www.homedepot.com/p/Bernzomatic-BZ8250HTKC-MAP-Pro-Hose-Torch-Kit-BZ8250KC/203391035

It doesn't get as hot as the full size model, but I figured it'd be really controllable, and a small focused flame - perfect for getting into tight spots or working around the gas tank.

Not sure if I'll return it yet or not but now I'm kind of leaning towards keeping it. I've had good luck in the past hearing a bolt and then spraying it with penetrant , having read that the heat pulls it in.
 
LarryJ said:
I'm just going to spray them every night for a week or even two, it's a project car so no need to rush.

I also bought this : https://www.homedepot.com/p/Bernzomatic-BZ8250HTKC-MAP-Pro-Hose-Torch-Kit-BZ8250KC/203391035

It doesn't get as hot as the full size model, but I figured it'd be really controllable, and a small focused flame - perfect for getting into tight spots or working around the gas tank.

Not sure if I'll return it yet or not but now I'm kind of leaning towards keeping it. I've had good luck in the past hearing a bolt and then spraying it with penetrant , having read that the heat pulls it in.
Click to expand...

That is a good looking setup. Keep in mind MAP gas burns hotter than propane. That is a good thing in this case.
 
It's not as hot as the regular torch, in fact benzonatic support suggested the bigger one for bolts (as opposed to this one, which doesn't list rusty bolts as a good use)

They wouldn't give me the actual temp difference ...but anyways, I also learned map gas is much cooler than it used to be, only about 100 degrees hotter than propane now. It was too hot for soldering previously (but better at busting rust loose)
 
Back to the original topic though, WHEN would you use an impact wrench? My understanding was it was great at busting rusted bolts loose due to the impact, but people still seem to prefer to go by hand for iffy situations .

And when you did, would you go full blast to start or start on low? This wrench in particular has a ton of torque, whereas my last topped out at around 450 lbs on paper, so just wondering if I should go easy or let'r rip.
 
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