Washington, D.C. Centre
the Spark


By Jim Lunson, tech committee


One of the real joys of restoring an old automobile is when you replace an old worn part with a brand new one and find the machine immediately perks up and works as well as it did when brand new, or often even better. Whether it is a new shock absorber, brake caliper, water pump, or merely a new valve cover gasket, there is a real satisfaction feeling when the new part fits right on perfectly and functions to bring that portion of the old car back to life. This satisfaction is probably why I enjoy restoring my MG and then driving it to appreciate my handiwork.

One of the biggest problems with changing out any part on an old car is not installing the new piece, but first getting the old one off. Being an old car, it is almost guaranteed that over time rust to some degree has formed on the part, bolt, sleeve, or whatever holds the particular part to the car. Rust is a reaction between steel and moisture (primarily moisture in the air) that eventually causes the steel to disintegrate into a powdery mass of iron oxide. One of the things that occurs during the early stages of this process is that the rust reaction with the steel causes the steel to swell. This is especially bad on screws, bolts, sleeves or any tight fitting piece on the car as the swelling causes the pieces to be bound tighter than ever to each other, making disassembly a real nightmare. There are a few tricks I have learned over the years that may help the situation.

Liquid penetrant: I have found the first step in removing a rusted screw or bolt that wont budge is to try the use of penetrants. These work to chemically dissolve the rust, relieving the pressure caused by the swelling. The trick here is to get the liquid into the joint where the rust is causing the bind. There are several brands of these penetrants on the market at the local hardware store. Below are the results of a survey Machinist's Workshop Magazine once did on the various products and the torque force needed to free up identical rusted bolts after treatment. The results are the end product of how well they dissolve the rust and how well they get into the joint to do the job. Interesting comparison:

ITEM                    Force in ft/lbs
No Penetrant.......... 516 pounds
WD-40................... 238 pounds
PB Blaster .............. 214 pounds
Liquid Wrench ....... 127 pounds
Kano Kroil .............. 106 pounds
ATF-Acetone mix*.... 53 pounds

*ATF-Acetone mix was a "home brew" mix of 50 - 50 automatic transmission fluid and acetone (pretty volatile stuff but apparently really works).

Although I have not tried the ATF-Acetone mix, my experiences have found the results from this test, using all the other products at one time or another to be about right. I generally use Liquid Wrench, and have a bottle of both the liquid and aerosol spray handy all the time. The liquid works better, but the aerosol is good when access to the part is upward and the liquid wont flow there. The others cost more and I dont think work nearly as well. The importance is to get as much of the penetrant onto the offending part as possible and then let it soak in the joint for several hours if possible. This allows it to work on the rust. Also a few short raps with a hammer sometimes will cause minute openings in the rust to open where the stuff can seep deeper into the joint, freeing up more of the jam.

Once this is done, the idea is to put as much torque on the bolt or screw as possible, of course without shearing off the head. Often on moderately rusted bolts this treatment alone will do the trick where the bolt totally refused to budge before treatment. Just takes some patience or forethought to put the stuff on some time before you are ready to go to work.

If you apply too much torque, head will probably shear off.  At least at this point, the part is released and you are then left with a stub of bolt to work with. But this is better than nothing as vise grips can often work to turn the shaft, plus you can now get penetrant much deeper into the joint. One trick at this point is to also try slightly tightening the bolt too. Since the head is gone, the pressure has been relieved and sometimes movement in this direction is easier than loosening the bolt, and once the rust bond is broken, unscrewing becomes much easier.

Heat: A second idea to get a bolt loose is the use of heat, usually through the use of a propane soldering torch. Often if the penetrant does not do the trick, applying heat to the part may help. The heat expands both the bolt and the hole into which it has rusted onto. Sometimes this expansion will break the bond between the two surfaces allowing the bolt to begin to turn. So fire up the torch, hold the flame on the bolt until it becomes red hot, let it cool, and repeat again. You cant see it, but expansion and contraction of the parts is happening. One note of caution with this technique is that there are a lot of flammable materials all over a car, so care must be taken not to get too close to either, oil, gasoline, grease, brake fluid, any plastic, including wire insulation or even the penetrant we tried first. Please dont use the torch to get the bolts loose that secure the gas tank or you may get the tank off much sooner than you want to. Often it is difficult to reach to even get to a bolt, not to mention trying to get a torch to it and not get the flame all over other materials. But with the proper treatment, this kind of heat will free a bolt that otherwise was stuck tight. Plus sometimes, a little heat will break some of the bond and then the use of penetrant again will get deeper into the joint and be successful at this point.

This is my first line of treatment when it comes to getting a stubborn bolt or screw loose. I have several more techniques I have learned while working on my cars which I will cover in later issues. These include excessive torque (pry bars), screw extractors, impact wrenches, and drilling out and rethreading. These methods all have a place, have tricks to make them work better, and cautions to avoid. In restoring or just working on an old car it will be inevitable that this stuck bolt problem will arise somewhere, and starting with these ideas may save some time, aggravation, and frustration, allowing you to move on to the much more rewarding process of installing new parts.


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