Legacy brake issue

[SubbieEm]

Hey guys so I’m looking for some answers on what’s going on with my brakes. My issue is on a 2019 Legacy.I step on the brake and even though I have consistent pressure the pedal drops down slightly on it’s own. I only notice it in the cold weather here in Alberta. I did have my brakes fail on me last winter (-43). I had my foot down to the floor ( which took some force) only to slowly come to a stop. The husband flushed and bleed the brakes, all was fine until again this winter. Any suggestions? Thanks

 

[bmart]

How long was the prior flush to the one you did? There could be bits/crust in the system still. Return circuit could be partially blocked. Are the pads wearing uniformly on each caliper? Any prior accidents?

 

[keith3267]

Bleed again without flushing. If only one caliper has air in it, then replace the rubber hose to the caliper first. If air gets into that caliper again, then replace the caliper itself, but it is more likely to be the hose. Possibly the hose is not tight at one end or the other. When you replace the hose (if) check the flair at the hard line very closely, if it has any deformity, then the hard line will have to be replaced, probably best left to a professional.

 

[bmart]

How would one bleed without flushing?

 

[keith3267]

Flushing is a process of replacing ALL your brake fluid in the system. Bleeding is just getting the air out. The processes are almost identical but to make a bleed into a flush, you first suck out as much brake fluid from the master cylinder reservoir as possible and then refill. The you can either gravity flush by opening the bleed valves in the order specified and making sure the reservoir does not go empty, or follow the bleeding process in the order specified but instead of stopping when all the air is expelled, you continue until you get clear brake fluid coming out the bleed valve. Again, do not let the reservoir run out of brake fluid.

A brake flush interval is in the maintenance schedule of your owners manual. Because modern disc brakes systems are not sealed like they used to be in the old drum systems, moisture can get into the brake fluid, lowering its boiling point as well as raising its freezing point. It has to be flushed according to the schedule in order to prevent brake failure.