minor welding triumph

Aug 05, 2004 5 Replies

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Dave Wilson 21 years ago

I was replacing the water pump on my Jeep Cherokee inline 6 (it lasted five years) and as I removed the last bolt I twisted the head right off. I got the pump off, but now I was faced with a stud sticking about 3/8" out of the front of the block. I tried all my tricks, like vice grips, and sawing a slot in the end for a screwdriver, and putting a torch on the stud, but nothing worked. Then I remembered reading a Lincoln manual from the 1940's that talked about welding a nut onto the end of a broken bolt. So I got an oversize nut, and used the mig to tack it onto the end of the stud, and then weld it on solidly. It wound right out with a wrench. I'm sure the heat from the welding helped loosen the stud also. Anyway, I was really glad to own a welder.

I was a little worried about frying the engine computer, but I took the ground cable off the battery before I welded, and the car ran fine when I was done.

Dave

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Doobie 21 years ago

Glad to hear it worked for you ( I have done that trick serveral times with

90% success) But your idea with heating the bolt is wrong, as that would cause the bolt to expand making it even tighter...you would want to heat a small area of the block so the threaded area would open up. As far as frying the vehicle's computer...as long as you place the ground close to where you are welding it will be fine as electricity always takes the shortest path.

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billh 21 years ago

I am going to disagree with you Doobie. I do agree about the relative expansion of the bolt and the block but I think there are some secondary effects of heating that cause frozen bolts to come loose. I have had too much success with heating bolts over the years to say it doesn't work. Billh

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Ken Moffett 21 years ago

Me too. The heating and cooling will loosen frozen bolts. I don't know exactly why but it does.

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Leo Lichtman 21 years ago

"Brian" wrote: (clip) The mig welding didn't touch the aluminium, stuck only to the steel tap and the helicoil. ^^^^^^^^^^^^^ How many diameters deep was the hole?

And, I guess your point is that while this works in aluminum, don't try it in steel (?)

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Ms_Squiggles 21 years ago

I have also had great success with heating stuck bolts to free them. I have a theory as to how it works. Doobie is partly correct with saying that it causes the bolt to expand and get tighter in the hole, the effect this has is to crush the particles of rust and crud that are jamming the thread.... when the bolt cools a bit, it starts to shrink back to near it's original size.. leaving the crud that had been jamming it crushed.... Result, one free bolt!

Another thing I believe happens is the threaded hole gets stretched just a little by the pressure exerted by the expanded bolt. This also tends to crush the bolt just a tiny bit too, making it a micron or so smaller.

I also agree with the theory of driving excess moisture out of the crud as Ecnerwal suggested, making this crud take up less space.

In fact it is probably a combination of all 3 effects that loosen it.

Pip

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