On Thu, 21 Jun 2012 11:00:29 -0600 Craig <[email protected]> wrote:
> On Thu, 21 Jun 2012 10:21:00 -0600 Craig <[email protected]> wrote: > > > On Thu, 21 Jun 2012 06:38:59 -0400 Max Dillon > > <[email protected]> wrote: > > > > > Does this sound like the bolt was replaced with an inferior > > > substitute? > > > > It does indeed. > > I checked the head with a magnet. It's aluminum. That means the > following information from http://www.prograbit.com/Pages/faq.php > applies: > > -------------------------------------------------------------------- > Q: How do you remove a steel bolt from an Aluminum engine head? > > A: During operation of the engine, it is subjected to high temperatures. > When the engine is then shut off, the temperatures return to normal. > This occurs very often during the life of the engine. Since the > coefficient of thermal expansion of Aluminum is approximately double > that of the steel bolts the mating threads of the bolt and engine head > are subjected to much pressure. When the mating surfaces of the threads > come in close contact with each other, an atomic bond can form between > them. They actually weld together. This condition is called "galling." > Galling is caused by various conditions including high contact pressure > and heat. If galling is not excessive, try the proceedure [sic] from > the previous example. If extraction is not sucessful with this method, > remove the Drill-Out® from the broken bolt and proceed as follows: > > Apply heat with a torch to the inside of the hole that you drilled into > the broken bolt from the previous procedure. Do not apply heat to the > Aluminum head. The purpose is to rapidly heat only the broken bolt. > Next, rapidly cool the broken bolt by applying water or some other > non-flammable coolant inside the hole. Because of the difference in > thermal expansion, the rapid heating and cooling will cause movement > between the mating thread surfaces. This movement should break the bond > established by the galling. Since we are talking an aluminum head with a hole in it and a steel bolt that goes into the hole, this doesn't make sense. A hole in something that expands when heated will get larger when that something is heated. The best way to separate the threads should be heating the head and chilling the bolt. > If this proceedure is not sucessful, then the galling is too excessive > and the broken bolt cannot be removed by extraction. After following the > above proceedures, you should have a broken bolt with a centered hole > drilled through it. Use a tap drill for the size of the broken bolt. > Drill and retap the hole. > -------------------------------------------------------------------- > > Perhaps that's the reason I am having trouble getting the bolt out. > > > Craig _______________________________________ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
