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Steel Bolt in Aluminium

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  • Steel Bolt in Aluminium

    I am at present taking apart a Perkins P6 Diesel engine, the generator adjustment bracket is secured by a 5/16 bolt that goes through a 2" long
    hole in the outside of the aluminium timing case, I do not think that the bolt is screwed into the timing case as there is a nut on the threaded end.
    But it is frozen solid , will not drive or screw out, has anyone had experience
    with this situation.

  • #2
    Originally posted by R W
    I am at present taking apart a Perkins P6 Diesel engine, the generator adjustment bracket is secured by a 5/16 bolt that goes through a 2" long
    hole in the outside of the aluminium timing case, I do not think that the bolt is screwed into the timing case as there is a nut on the threaded end.
    But it is frozen solid , will not drive or screw out
    Would this be a marine engine that sees salt water service?
    I am just asking because it sounds like it is too me.....pg

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    • #3
      Ok I have not worked on this engine but I have a few ideas. There is probably corrosion along the bolt in the timing cover. I would try soaking it with penatrating oil and tapping the head with a hammer before tring to remove the bolt. If that does not work and you want the cover off drill off the head of the bolt so you can remove the cover. Then you will have the remaining 2" left. I would try to use vice grips to turn it out. If that failed drill the bolt out and tap the hole.

      Edit: Does this bolt pass through the generator housing? If it does can you drill it out and replace it? Post a pic if you can.
      Last edited by Rookie machinist; 05-08-2008, 01:28 AM.

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      • #4
        You bet RW, any one that has done mechanical work for years has experienced that, called dissimilar metals problem. very common with un-anodized aluminum and steel bolts. Have had some success with torch heating the aluminum, use caution as it will let go and melt if you are not careful.
        Try tightening just a bit at first and then loosen.

        Re-assemble with a liberal coating of anti-seize compound on the bolt.
        Had some where the part just had to be replaced as I could not get the bolt out no matter what.

        Be patient and do as Rookie Machinist suggested by hitting the bolt head with a hammer, this vibrates the bolt helping the penatrant to advance and aids in breaking loose the corrision.

        Ken

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        • #5
          Originally posted by piniongear
          [COLOR=Blue][SIZE=3][FONT=Comic Sans MS]Would this be a marine engine that sees salt water service?
          It is a tractor engine, Massey Harris 744D.
          Thanks for your replys. R W

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          • #6
            As well as the other suggestions, an air or electric impact wrench might help.

            Tim

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            • #7
              Ken Shea has the correct method posted. Aluminum expands at a faster rate than steel when heated and should break the corroded bond. Be very careful as the 5/16 bolt will be weakened by the corrosion also. JIM
              jim

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              • #8
                Suck up a small amount of battery acid from a battery and dilute it by adding it to an equal amount of warm water. Add several drops of liquid dish soap to reduce surface tension. Apply to the bolt where possible and allow it to sit for at least several hours. Aluminum is not affected by sulphuric acid at all so it won't damage the case. It will dissolve any ferrous component of the corrosion that it can reach. After several hours apply a boiling hot solution of water and baking soda. This will neutralize the acid and will also cause differential expansion of the metals with no chance of overheating the aluminum.

                This is the process used when I worked on aircraft floats.
                Free software for calculating bolt circles and similar: Click Here

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                • #9
                  I would give it a couple of good sharp cracks with an impact driver to shock the bolt, then try releasing it.
                  Peter - novice home machinist, modern motorcycle enthusiast.

                  Denford Viceroy 280 Synchro (11 x 24)
                  Herbert 0V adapted to R8 by 'Sir John'.
                  Monarch 10EE 1942

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                  • #10
                    Originally posted by Ken_Shea
                    Re-assemble with a liberal coating of anti-seize compound on the bolt.
                    Had some where the part just had to be replaced as I could not get the bolt out no matter what.
                    And make sure it's anti-seize for Aluminium, the copper based stuff actually promotes differential corrosion in a steel/Aluminium/water environment,
                    Nick

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                    • #11
                      Years ago my Dad and I had a Wisconsin V4 engine where the cylinders had rusted stuck. We took off the heads and poured oil in each cylinder and it ended up sitting that way for a couple of years. Still was stuck. After talking with a local machininst, he suggested using Coca-Cola. Within three days, the cylinders were moving.

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                      • #12
                        What is going on is called "Galvanic Corrosion". It happens all the time with dissimilar metals.
                        Here is a link with a little info for your reference:

                        http://en.wikipedia.org/wiki/Galvanic_corrosion
                        "Those who hammer their guns into plows will plow for those who do not."~ Thomas Jefferson

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                        • #13
                          I've been an outboard wrench for over 30 years and know exactly what you're dealing with. Heat is your friend on this one. You need to heat the heck out of the casting, because that casting will suck all of the heat you put in the area of the stuck bolt until the whole thing is pretty warm. The best thing to use is an acetylene tubo (air)torch. Propane takes forever, and with oxy/acetylene you run the risk of melting the casting (and that can happen all of the sudden, before you have the time to react). If all you have is oxy/acetylene, make sure you have a carburizing flame to reduce the meltdown risk. Once you have it to where you think it is hot enough, heat it for 5 minutes more and you should be able to drive or turn the bolt out.
                          Mac

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                          • #14
                            Originally posted by smiller6912
                            What is going on is called "Galvanic Corrosion".
                            If the object were small enough (say, a Harley transmission or engine case) to submerge, would the electrolytic rust removal process be effective at penetrating the bolt shaft and threads and separating the corrosion between the steel and aluminum? What would be the effect on the cast aluminum case? My problem trans case:

                            Last edited by Bob Farr; 05-08-2008, 03:13 PM.

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                            • #15
                              It works pretty well on assemblies that are left assembled. Here is one I did that was pretty well rusted up. After the treatment the rollers turn freely after a bit of oil.




                              Free software for calculating bolt circles and similar: Click Here

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