Freeing corroded parts

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alan s
RIP 2010
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Joined: 26 Jan 2001, 16:53
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Freeing corroded parts

Post by alan s » 06 Aug 2003, 05:33

We often get postings from people having problems loosening parts that have corroded in and predictably, these all too often all end up in tears when something like a brake bleed nipple sheers off in the caliper or a rear sphere is so tight that the rear cylinder turns & takes out all the plumbing in the process. As a former tradesman working on items prone to corrosion as well as owning a boat used exclusively in salt water, I can pass on a couple of general hints that may help make life a bit easier and the job quicker when these situations become part of the problem.
Firstly, assess if the part you are trying to remove is <b>tight</b> or <b>corroded.</b>
If <b>tight</b> then possibly an impact tool is the most logical choice to rattle it free, however if <b>corroded,</b> then an inpact tool is the last resort due to their tendency to sheer things off in this condition.
If corrosion is suspected & if the job is planned for say a day to a week later on, start by spraying WD40, Penetrene or RP7 onto the threaded area or in the case of bleed nipples, where they screw in. Repeat a couple of times to ensure that the circumference is circled in the stuff, but notice something, particularly if it's a bit rusty? The penetrating agent (WD or whatever) quickly disappears! To counteract this, a couple of drops of engine oil on top of the penetrator works wonders as in time, it tends to follow the track made by the penetrater. This works on <b>ALL metals.</b> Even a dollop of grease in certain situations can work wonders but remember as always, common sense must prevail if working around brakes as far as contamination is concerned so use in moderation and don't get these lubricants onto anything associated with brake surfaces.
<b>Using HEAT:</b> This is a method that is often used incorrectly; when someone suggests heat, the first inclination of most is to reach for the oxy acetylene and start getting things almost white hot, almost melting the entire job & ripping & tearing away at the stuck bolt whilst usually ending up with blisters & burns all over their hands in the process & often causing more damage than they would with a sledge hammer. <b>Heat,</b> particularly where two different metals is concerned, is there to do a job; cause these metals to expand & thereby break the seal between the two offending surfaces, nothing more, nothing less, hence used correctly, little brute force is necesssary. The system I use is this:
If it's a small object such as a bleed nipple, use a pin point flame such as you get with a mini (butane) pocket blowtorch. In the case of a larger object an LPG blowtorch is ample. Oxy in moderation is OK but don't get heavy handed with it. If it's steel (nipple) heat to dull red - <i>just the nipple.</i> Allow to cool to touch temperature. Then, use a <b>hexagonal socket</b> (one with 8 sides not 16) and try to move by firstly applying a slight pressure & if no luck, by bumping the end of the handle with the ball of the palm of your hand. If it still sticks, put more fluid on the thread and give it another half to one hour to again soak. Reheat again to the same temperature and again wait for it to cool to just above touch temperature & if no luck wait until nearly cold & try again. Rarely does it go past two goes but I have gone to 4 on a couple of occasions. The general principle is that is expands & contracts and usually when you strike one expanded whilst the other has contracted to its original size, there is a cracking of the seal created by the corrosion & it all just screws apart. If however, all seems lost & it won't come apart, then resort to the 'rattle gun' as you've got nothing to lose!
In the case of alloys, then the penetrating agents are a must, heat to the maximum which I use WD & spray it onto the area being heated with flame withdrawn & when the WD instantaneously just turns to white vapour, you're at the limit of the metals ability to take the heat.
Whenever you reassemble any job on the exterior of the car, always but always, coat the thread & shafts of the bolts with grease it saves an awful lot of work down the track if that area has to be revisited. I have made this a policy on my outboard motor ever since I bought it new in 1974 and I still can pull bolts out usually without resorting to drastic measures; that should tell you something.[:D]
Alan S