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, Sat, 9 Apr 2005 09:57:50
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I suggest this to avoid any need to bleed, has worked for me on other MCs over the years.
Remove the old one, refit the new with reservoir. Add fluid with the two hydraulic lines very loosely connected, so that fluid is leaking freely from these connections. You need a container and/or lots of rags to catch the leaking fluid. Now pump the brake petal to flush air from the MC and this will not go into the brake lines. The petal will feel very soft. Now tighten the hydraulic lines to prevent further losses of fluid. At this point you are probably good to go. But when you are doing this work, observe if fluid was leaving the ends of the open hydraulic lines. If fluid was draining out, air was getting in, and this would be a limited amount. You can now move some of the caliper pistons in to displace fluid back to the reservoir and this will server to back flush out any air from the ends of the lines and any that migth remain in the MC itself. Then the petal can be pushed to advance the caliper pistons back to the rotors. This will require that you remove at least two wheels to get at the calipers. The brakes system is a split system, so you have to work on both sides of the vehicle to geet fluid to back flush both lines.
There may be an advantage to working quickly to reduce the time that the brake lines are open... if they show any tendancy to have fluid leak out. Once the lines are loosely inserted into the new MC and fluid is draining out of the loose joints, air intrusion is arrested. So remove the lines after the mounting fasteners are removed.
After you do this, you can bleed the system, so having the wheels off is then probably something that you wanted to do anyways.
It does not make any sense to flush air from the MC through the system from one end to the other.
To avoid MC damage, renew the fluid at the reservoir every year. Do this prior to any bleed as the fluid at the reservoir is the most moisture contaminated and you don't want to push that through the system. These reservoirs that vent to atmosphere are totally stupid. Detroit vehicles had rubber diaphrams separating the air from the fluid many decades ago. So a solution is at hand.
Brake fluid is water soluable, so cleanup is a simple water rinse, for hands, tools and under the hood.
Once a MC bore starts to rust, this can cut the MC piston cup seals. The rust does not form on the traveled part of the bore, but beyond that. If one pushes the petal to the floor during a brake bleed operation, that when the damage occurs. So one should always limit petal stroke. A wooden block behind the petal to limit travel when doing the work is a very good practice.
A MC bore can often be cleaned up and an overhaul kit installed which consists of a new piston and seal assembly etc. I have cleaned up the bores with wet/dry sandpaper with a flow of water. Shake or blow dry (must be oil free air), and heat or bake to dry further. If the bore is pitted this might not be viable. There used to be small 3 stone hones for this to recondtion the bore. This tool was used with an electric drill. Have not seen one lately, but probably are around. This might not be a good option if this is your only daily driver, as one needs to tear it down and evaluate, the order the complete MC or an overhaul kit. The piston cup seals are compliant and the actual diameter of the bore does not have to be an exact and never changing size.
A hone should never be spun in one location, but must be moved in and out constantly when turning. Depending on the grit and finish, I suspect that I would want to finish off with a fine wet/dry sandpaper afterwards. When assembling the MC, one might be able to charge the bore with fluid as part of that operation. There are brake assembly lubricants that can be used, but I don't know if these are on the shelves or not. These assembly lubricants are rust preventative. Components that have brake fluid in or on them have no shelf life and cannot be stored.
, Sat, 9 Apr 2005 09:57:50
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