Sheared bolts - impact gun better?

[John_B]

Alright Brain-trust.

I knew it was going to happen, it was inevitable, but it still hurts. I sheared two bolts last night attempting to remove the thermostat. I have an action plan after reading a few threads of people finding themselves in a similar predicament, and hopefully will get the studs out before it comes to disassembling the head.

But it has got me thinking about future wannabe sheared bolts (water pump, I'm looking at you!) - would using an impact gun be a better choice for avoiding them in future (checking and double-checking it is on loosen mode before pulling the trigger ) ? The impact! nature of the force applied, as opposed to the loooong molecule bending force of a wrench.

This may be totally obvious (or obviously wrong), but I thought I should check my logic before making a bad situation worse!

 

[Rudyrov]

"IMHO"- Depends on why they sheared, if the bolt is frozen in the metal an impact might not help.
Perhaps heating and soaking the bolts with penetrating oil for some time would help, sometimes there is not much that can be done to prevent this.
Bolt gonna Bolt

 

[Pond]

I agree with the above. If a bolt is weak then an impact wrench will just snap it quicker.
I have a mahoosively powerful mains impact wrench which is great for big stubborn bolts but not any good for anything else TBH. You do have to hold on tight!
I have a mate, a life long mechanical engineer (not cars), who swears by using a big spanner and a small hammer at the same time. Small quick taps with the hammer at the bolt end of the spanner whilst putting pressure on He reckons it's better than an impact driver, as you can determine yourself how much 'welly' to give everything rather than a set amount applied by the impact tool.

 

[bear2020]

Makes no difference the bolt sheared. It only shears when the stress applied is greater than the shear strength of the bolt, but being in the location of the engine it is also subjected to corrosion which will reduce its shear stress. I have found sometimes it is better to "Shock" a bolt before attempting to undo it and apply force. But bottom line is if it is going to break it will do it in the most awkward place to get it back out!

 

[Pingu]

If a bolt is going to shear, an impact gun will definitely shear it. Impact guns are excellent at removing fasteners that are in relatively good condition, even if there is lots of surface rust on the threads. The fasteners may need to be loosened, PlusGas'd and wire-brushed, and tightened a few times before coming off. Use the lowest setting that will do the job.

I make sure the exposed threads are clean and PlusGas'd. WD40 is pretty useless compared to PlusGas.

Try to make sure that it is only torque that you are applying. It's very easy to add bending. Try to apply the force as close to an imaginary line perpendicular to the weakest part of the fastener.

Apply the torque gradually, but stop before you feel it yield. You can use extensions if required. Then TIGHTEN the fastener. Apply PlusGas. Try to undo again. Apply max torque that feels ok, then tap the fastener and the end of the spanner (whilst max torque is applied).

You can try heat if there is nothing nearby that will burn.

Waterpump and thermostat studs are always affected by corrosion, will probably not succoumb to any encouragement, and will shear more easily than any other studs or bolts.

I didn't plan to publish this, as it's not as good as it could be, but it shows some of the techniques. Notice how the spanners are angled to reduce the bending forces...

 

[John_B]

Thank you all for your advice, it is greatly appreciated and I shall leave the impact gun for now

 

[t-tony]

It's a good idea to try to tighten a bolt before trying to loosen it. Doesn't always work but more often than other it does. When you have something like this in bits grease the bolts lightly before refitting them. NOT oil, Grease.

Tony

 

[Trevor /chedder]

This happened to me on my thermostat change. Iwas lucky and a bit or bolt sticking out so was able to hammer on a cheap small socket and get them out. Good luck!

 

[bear2020]

I always put a punch on any bolt before I take it out and hit it a couple of times on the head off the bolt. It shocks the bolt and helps loosen the thread if it has corroded. Using grease is fine on a bolt if you are going to torque it. If you are not going to torque it leave the grease as it does allow you to over tighten and then you can shear the bolt by tightening.

 

[John_B]

I always put a punch on any bolt before I take it out and hit it a couple of times on the head off the bolt. It shocks the bolt and helps loosen the thread if it has corroded. Using grease is fine on a bolt if you are going to torque it. If you are not going to torque it leave the grease as it does allow you to over tighten and then you can shear the bolt by tightening.

Thanks, that's a good tip about the punch, I'll add that to my choreograph when I tackle the water pump!

 

[Zephyr]

I usually pray.
But tightening and then twisting some degreees, clockwise and anti clockwise while spraying some penetrol works.

 

[bear2020]

Thanks, that's a good tip about the punch, I'll add that to my choreograph when I tackle the water pump!

Working offshore on platforms on bolts that have not been touched for 30+ years corroded by sea water & air you learn a few different ways to undo bolts. If I can get to hit with a hammer I will do that but on a car most times you need a punch or even a block of wood. You are only shocking it to break any corrosion within the thread and whatever it is screwed into

 

[John_B]

It's been soaking in penetrant for the last 36hrs, later today I am getting a can of freeze spray delivered, so the plan is hit it with the heatgun (or butane torch if I am feeling brave) then the freeze spray, a whack with a hammer and then vice grips.

I did order some stud extractors, but they are too chunky to fit with the timing case cover

 

[bear2020]

I hate mole grips! If you have two nuts put them on and tighten them up against each other and then put a socket on them and then try to undo it. Once you get mole grips on they chew everything up and prevents you trying to use any other type of method to get them out

 

[Andyboy]

When replacing a plastic thermostat, I use a hammer and screwdriver and break it up in situ, leaving the bolts in place. Then you can grind the bolt heads off, remove the steel sleeves and remove the remains of the bolts with two nuts locked together using WD40 or similar.

 

[Andyboy]

Same with ABS sensors. Try and undo the allen bolt and chances are it will break. Destroy the old sensor leaving the bolt intact and it comes out easily.

 

[Pingu]

That looks like an old socket might be a good bet. You should be able to hammer it on all the way up to the face.

 

[John_B]

That looks like an old socket might be a good bet. You should be able to hammer it on all the way up to the face.

I'm wondering if you have been spying on me, because that is exactly what I just did, and what worked! Thanks to @Trevor /chedder for the suggestion!

Water pump bolts all came straight out, now it's the pump itself that doesn't want to budge! I tried to use the threaded holes top and bottom, but they broke off almost instantly

Now I am going off-script!

 

[John_B]

 

[Pingu]

That tool looks pretty good. Also use a BIG hammer with light taps on the edge of the pulley. I have the head of an 8lb sledge for such occasions.