hi folks ,every time i work on my brakes i seem to need to bleed them afterwards , Is this normal . ive always thought that when you work on ur vehicles brakes u must remove the cap from the brake fluid reservoir , however every recent article with hints and tips have no mention this , is this why i need to bleed them ?
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Depends on what you've done to the brakes.... you shouldn't have to bleed them, unless you've opened up the hydraulic system (removed a hose/bleed nipple/or pistons) If you have just pushed back the pistons, to fit new pads, you shouldn't have to bleed the system, but you WILL have to pump the lever a few times to bring the pads back into contact with the discs.. Normally, there is no need to remove the reservoir top, unless you want to add/remove some brake fluid.
There are cheap, crap cars,.... and there are expensive, crap cars,... take ya pick........
This is my understanding:-
Really the reservoir cap and especially the rubber diaphragm/bellows should be removed as little as possible, to avoid the fluid becoming exposed to air. It is hygroscopic.
Most of the trapped air in the system will be vented out into the reservoir, with only a little left to expel out the nipple. But this is only when filling the system from empty. Once filled and vented it should not need bleeding periodically unless there is a problem.
It is recommended that a technique is used to expel any possibility of air becoming trapped under the bellows when it is fitted/refitted. Air under the bellows won't necessarily affect the principle of operation, but the reason is to avoid contact with air, thereby preventing absorption of moisture. The technique needed is messy and will result in fluid being displaced over the top, so have plenty of clean rags to catch it.