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Discussion Starter #1
I have used pneumatic impact wrenches of various sizes and peak torque in the past to remove stubborn fasteners. They either remove the screw or break it.

A friend is having problems removing a bleeder screw on his Honda. He maintains that whether you use a constantly increasing torque, using a slide-bar driver by hand or an impact driver, that it makes no difference.

I have no explanation other than the impact driver helps break the static bonds preventing the screw from being removed. Possibly overcoming the static forces bonding the corroded fastener to the caliper might be why impacts work. Preventing the fastener from turning.

The behavior of a steel fastener frozen in aluminum seems also different than the same fastener in alloy steel. The aluminum seems to grow as it corrodes turning into Aluminum oxide which puts an incredibly tight grip on the fastener. Keeping any ‘Liquid Wrench ‘ or ‘PB Blaster’ etc from penetrating into the threads. Preventing the fastener from turning no matter what you do short of using heat. Since heat is not good for the seals, using it is out of the question if all you are looking to do is bleed a caliper.

Can anyone shed any light on the subject of properly loosening bleeder screws? Naturally without damaging the caliper or bleeder.

I have used brake assembly paste in the past. All it takes is a small amount of the paste on the bleeder threads to successfully prevent corrosion of the bleeder. The paste I use is made by Castrol but AGC also makes a much cheaper rubber compatible brake grease.

http://www.amazon.com/AGS-Company-Sil-Glyde-Brake-Lubricant/dp/B000CIHTPE


Any opinions on the AGS lubricant?
-Radar
 

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I have used rapid heat and cool cycles with success:

Propane torch to the bleeder only, I used a sheet metal heat shield (just a piece of sheet metal with a hole in it, placed over the bleeder to direct the flames from the propane torch away from the caliper).

Use the propane torch with the flame blowing sideways away from the dust plate and away from the caliper. Heat up the fitting, then when hot, a dribble of pb blaster/pb catalyst to quickly cool the bleeder.

This heat cool cycle expands and contracts the bleeder, and hopefully breaking that bond between the bleeder and the caliper. I do this multiple times, trying to loosen it after each time, only using enough muscle to "break it loose" but not too much to break the bleeder. Just a subjective "feels about right thing". Don't let the bleeder cool slowly or it will become soft and break easily when wrenching it.

Putting a small socket on the bleeder (or a small piece of pipe) to protect the nipple at the end of the bleeder, and pounding on that pipe or socket (to shock it) can also help some. Again, hitting it, heating it, pb blaster, and repeat. The pipe should fit over the nipple but not slip over the hex head portion. Just use common sense when hitting. No 5lb sledge used here!

Once I did this for 3 days straight on a dodge, probably 3 times each day, finally the bleeder broke loose. Thats my version. KD
 

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I get the willies every time I try to loosen my bleeders.

As far as method, I don't logically see how it can matter what method you use. I think it is all about peak force applied. I can sort of see how a pneumatic impact wrench might be less likely to break something, but I don't think that corroborates well with real world experience.

Techniques with the torch and PB blaster and all are great secrets to get to learn at a place like this.

Interesting to think about.
 

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Discussion Starter #4
I have used rapid heat and cool cycles with success:...

" Don't let the bleeder cool slowly or it will become soft and break easily when wrenching it."

KD
Are you indicating that the temper of the bleeder might change?

In theory the alternate heat/cool/heat cycle will help. I personally find using heat a little on the risky side on brakes. Not sure what it does to Dot-3. In addition the Dodge caliper is probably more massive. And forgiving.
I will pass this and any other suggestions on.
-Radar
 

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Yes, I am regarding the temper of the bleeder. Oil quenching it while hot (pb blaster) keeps the temper. Letting it cool slowly will leave it soft and will break easily when torque is applied.

It is common to heat up a piece of metal, let it cool slowly, machine the metal (work the metal while soft) and then when done machining, heat it up again and then quench it to make it strong again. Do a google search. Lots of info.

I did this last year with a bolt. I needed to make an odd size thread insert. So basically I wanted to drill down the center of a threaded bolt and cut threads in that newly drilled hole. I was having a heck of a time breaking bits, breaking taps, etc.

Then after a little reading on the internet, I took the same bolt, got it cherry red (I used my wood burning stove), then let it cool slowly. It drilled and tapped like I was cutting through soft brass. Piece of cake. After the hole and threads were cut, I put it back in the wood burning stove, got it red again, took it out and dropped it in a container with some oil. Bolt was hard again.

That part has been in service for over a year now. It was used to fix stripped threads in a cast aluminum engine case of a chainsaw. The holes for the bar bolts were stripped and heli-coiled multiple times before I took ownership of the saw. It is a 3ft long bar (lots of stress on just two bolts) mounted on a 97cc chainsaw. Got the saw cheap because of this. The custom thread insert did the trick. KD
 

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Discussion Starter #6
Heating bleeders to bleed brakes - is it safe?

Heat :eek:. As far as I know the temper or hardness of a metal is a little more complex process than shooting it with PB Blaster. It may indeed have been hard enough in your case but to get it back to original strength is not a simple process. I too have played with tool steel that is specifically made to harden under a specific conditions. To make custom tooling. But restoring the bleeder after it is cherry hot, I just don't know :rolleyes:

There is just something about using heat that - well to me - it just doesn't seem right in this case. There might be another trick used by the Pros, that just maybe doesn't require heat! Without having to replace the caliper or cylinder during bleeding that they would use on their own vehicle driven by their wife. To drive their kids to go grocery shopping or soccer practice etc.

Please enlighten us!
-Radar
 

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Discussion Starter #8 (Edited)
Heating bleeders

So there you are. Standard practice used for years.
As safe as the skin inspection in the Boeing 737...
Thank you very much for your participation.
-Radar
 

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You do what you have to do.

Auto mechanics do not get paid to be heros.

A smoke wrench is the mechanic's friend.

(Just don't ever heat brake flex hose fittings unless you intend to replace the flex hose, and are prepared for the old hose to explode during the heating process. Also be aware that brake fluid is flammable.)

If an individual wants to spend hours of their time struggling with a frozen brake bleeder or a frozen fastener, have at it.

If a bleeder screw cannot be loosened through normal means, then alternative methods / solutions are used.

A bleeder screw is not a fastener, it is a tapered seat plug. They are also quite cheap to replace if one is concerned over having altered the temper of a frozen bleeder during removal.
 

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Radar24; I believe you are absolutely correct about the impact driver. There is a humongous difference between applying rapid on off torque, and jumping on a 3' extension/cheater bar. The shear equation is not simply torque, it is torque x time. The problem is that with the continuous torque application, that occurs with a bar, you can easily reach the torque X time limit, that will shear off the fastener. The bond that is resisting the release of the fastener is very brittle, and the impact driver can hit it with 3 times the torque in 1/10 the time.
In the case of bleeders, I found a hand held impact driver, the type you strike with a hammer or rubber mallet in this case, to work very well. I would always replace bleeders anyways, since they seem to seize better each time if reused.
 

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Discussion Starter #11
Little black caps on bleeder screws

One method of helping the bleeders screws from freezing is the obvious one. That is replacing the little black caps on the end of the bleeder screws. The ones that get thrown out the first time the brakes are bled. By 50k miles they are usually cracked and disintegrate in your hands when you remove them. It is only part of the problem however as they only reduce corrosion inside of the bleeder screw and not at the exposed threads where the screws meets the caliper. Or cylinder in the case of drums brakes.

Previously I touched upon the method that has worked for me to keep the exposed threads from corroding. That is to remove the bleeders and to blow the threads on the screw clean of any brake fluid. Doing the same to the caliper when it stops dripping fluid. Then I coat the threads on the screw with brake rebuilding paste. Never with anti-seize or regular grease as that could contaminate the brake fluid. Should any of the paste get sucked into the screw. When the brakes are manually bled. With pressure bleeding contamination is not much of a problem except it is not known how the brakes will be bled the next time. So do not ask for problems and keep any grease away from the bleeder screw.

The caps are on the expensive side unless they are part of the seals that come in a seal kit. I have seen the caps go for a ridiculous $5 per cap retail. Does anyone know of a source at a more reasonable price? Caps that do not crack under the harsh conditions calipers get. Perhaps made out of Viton or another suitable material that does not crack so soon? Trapping corrosive salts inside the screw being even more problematic if they crack in areas where salt is used to melt snow and ice.

Yikes, I am going to start losing sleep over this! :eek:
-Radar
 
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