What is the best way to remove a stuck/rusted exhaust bolt?

Question

I'm trying to disassemble the exhaust system on a 2000-2003 Nissan Maxima and I'm having trouble removing one last bolt. It's got a 14mm head and its just plain STUCK. I've tried soaking it overnight with PB Blaster, then the next morning I tried removing it with a 2ft long breaker bar + a 2ft extension. After making absolutely positive I was trying to turn it the proper direction, I braced myself by putting both feet on a framerail and pushing with all my strength. And then, my socket shattered into a billion pieces.  Bolt: 1 Me:0.

S_Niles · Accepted Answer

My general rule for exhaust bolts/nuts is to order new ones with the part you are replacing, knowing full well that there is a good chance you'll destroy the ones you are removing. Better to be prepared ahead of time than to be stuck waiting for new parts from another country after you've disassembled everything. Personally, I have a rule of ordering every bolt and nut that is attached to the exhaust member I'll be replacing. Even if there isn't much rust, I never know when a bolt will snap.

First task is to let the exhaust completely cool. It's possible that the parts are made of different types of metal which expand and contract at different rates.

Now, how to get the rusted bolts off:

Use an impact wrench. Sometimes the vibration and hammering action works better to "knock" a bolt loose, compared to wrench/breaker bar. In my experience, this is the first tool of choice for 95% of techs working on an exhaust system.
Use a big breaker bar. 2 ft is okay, 4 ft is more like it. Use high quality, name brand tools that won't flex or shatter on you (or at least give you free replacements when they do shatter). The flexing is important. If the cheap breaker bar is flexing instead of transferring the full torque, you may as well not have it.

Sometimes there is just too much material rusted off of the bolt for either of the above to work. Or one of the above techniques may round out the bolt before it comes out. In this case, the bolt needs to be destroyed so you can move on with life. Some options are:

Die grinder with appropriate wheel.
Hacksaw / airsaw.
Air hammer with chisel bit.
In extreme cases, torch.

As always, use high temperature anti-seize when putting in the new bolts. They will go in easier, and the next person down the road will thank you.

Safety Note: All of the above methods assume you know the safety procedures for the tool. Of particular importance is having the vehicle properly raised on the car lift. Some of these methods involve violently pulling stuff around, which will cause the car to move.

Dude318is · Answer

If it's in a really tight spot, Dremels can work wonders too. I can't begin to tell you how many times I've had a bloody exhaust bolt seize on me.

Chris · Answer

I find heat is far more effective at removing stubborn bolts than PB blaster or the like.

connie · Answer

Doubt if my two cents is asked for but rust is oxidization. It's just burning real slow. Torch with a brazing or welding tip is best. The rust disdappears like magic when you burn it the rest of the way up. I find no need for red hottin' it. Cast iron is brittle. Get a 650 degree heat stick and warm things evenly and cool slow coveted all up in vermiculite. Manifolds crack, then we do. Be gentle

Answered by connie on May 26, 2021

user6909 · Answer

An old steam fitters trick. Heat and candle wax. Heat the bolt and push a candle against the bolt an threads. If you got the bolt hot enough it will draw the wax into the thread.

AF7 · Answer

Soaking in WD-40 or equivalent will help, but the real final measure is first a blowtorch - even a cheap and not-very-powerful one will do - followed by impact wrench.

Alternatively, you can buy hydraulic tools but they will probably snap the bolt leaving you with one more problem to solve.

Randy · Answer

I own a heavy equipment business. Sometimes starting the machine for a minute or two to heat up the head slightly will assist in freeing up a stuck bolt or stud. Turn machine off then quickly attempt to remove bolt before heat transfers to it.

Answered by Randy on May 26, 2021

tododo · Answer

Acetone and vegetable oil is superior to any store-bought oil of the same purpose (yes even kroil), as shown in lab experiments from Drexel University.

Drexel team’s final report.pdf

Andrew · Answer

I have just removed a very rusted exhaust flange bolt from the bottom of the "Y" section on a Nissan 350Z.

I had already broken the joint with the center section. To do this I cut the nut/bolts  with an angle grinder, which left two useless stubs of a rusted bolts in the "Y" section. I drilled out one of the stubs which took hours of effort using a Cobalt drill bit. When I recovered the offending stub (or what was left of it) I saw that it was located into the flange using a "toothed" taper, which prevents the bolt from turning when tightening the nut on the joint. This is obviously why there's no hex' head on these bolts.

Given that the taper was short and not too shallow, I thought I'd try to press the other stud out, rather than drill it. Most other sites suggest using copious heat / bashing techniques to remove, but the following is THE BEST and QUICKEST METHOD.

Get a long - reach and sturdy Ball Joint splitter, and locate the "forks" either side of the head of the stud. The forks must be clear of the head. Tighten the bolt on the splitter, and put some metal between the actuating arm and the tip of the protruding stud. This ensures all the force is transmitted to the stud. Tighten the splitter bolt and within a few minutes, yes MINUTES, there will be a loud crack, and out from the flange will pop the offending stud !! Clean as a whistle.

This leaves a perfect hole ready for a new (this time stainless steel) bolt.

robert andrews · Answer

Heat around the bolt,especially if you are taking steel out of aluminium, otherwise heat the bolt, he's right about oxidation, but I try to heat around the bolt more-so and metal expands and use just good half in. Drive and work it a little at a time - tighten a little heat it then loosen and usually you can keep from the big nightmare, breaking it and yes I have used a candle too. It sure can help - but if I know the bolt is really rusty I'll heat and turn till it feels like it's gonna break then tighten a little then reheat and so on. There is nothing much worse than breaking a manifold bolt off then helicoil or re-tap.

It's ironic I ran into this. I've been working on an 83 ford 351w and that is just what I've been doing. I was replacing valve seals, and this motor is a mess. I happen to notice it looked like gaskets were really burnt. Heck,it didn't even have a gasket on either one. I have 3 yet to loosen and stopped at 2.00 am. Off tomorrow. I hope to get this thing running half decent. I shold have driven it more before I bought it, but it'll be ok - it has to. So real good ideas I'll keep in my box of tricks.

Jeffrey Wilkinson · Answer

Blow torch and water. Heat the bolt red hot and then cool it immediately with water. Then it'll come off with your fingers. The extreme temperature change makes the bolt shrink which makes it super easy the come off. Done it many times, never failed.

Answered by Jeffrey Wilkinson on May 26, 2021

Carl · Answer

I have at times removed studs on car manifolds and been lucky replaced the stud and used a new copper nut, more troublesome are motorcycle exhaust manifolds on occasions the studs just break, the only option is drilling and carefully removing the shell, but if you use this method you must be careful not to over drill on some engines like BMW the oil ways run behind the stud, always measure the distance and mark the depth of the drill with masking tape to evert engine tragedy.

Answered by Carl on May 26, 2021

What is the best way to remove a stuck/rusted exhaust bolt?

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