Hi folks, Quick Query
I'm about to do a full flush on my brakes (Shimano Deore). They,ve been bled a few times but the bike is over 4 yo now and it could probably benefit from a full flush
I've had a look online and can find loads of info about brake bleeds but little on full flush
Can anyone direct me to the correct procedure for this
Do I just flush out the old oil using the new oil? If so how do I know that all old oil has been flushed out?
Or do I flush out with something else before using the fresh oil? Would it be beneficial to flush with Isopropyl Alcohol or am I just talking kack?
Thanks in advance folks
Just keep pumping in new oil. I suppose you could estimate the volume but if you can't tell if it is fresh or old coming out then it probably doesn't need doing.
Just keep pumping new in until you see fresh stuff coming out, it generally doesn't really mix, the new will come out behind the old, which will probably be a bit darker in colour.
If there's nothing wrong with them, leave them be. I have Shimanos that haven't been touched in 7 years and they work perfectly.
I’ve tried it this way a couple of times. IME it works really well.
Personally, I wouldn't bother. If I did, I would just open the reservoir and the bleeder on the caliper and let the old fluid drain by gravity, then use a syringe to pump fresh fluid in from the caliper. Any water in the system will have collected in the caliper, so this should ensure that the caliper is full of fresh fluid.
Push fresh oil in the caliper (with pads removed and bleed block in place), keep going until it comes out clear at funnel.
Close off caliper, do some lever squeezing and tapping of hoses.
Put screw back in reservoir, job done.
But as Scotroutes says, if there's no actual problem with how they work I'd leave well alone.
I had some Deores from about 2014, never touched them apart from new pads. Sold them in perfect working condition this year.
If it aint broke don't fix it.
I have Shimano brakes from 2003 that have never been bled and still work perfectly. Mineral oil isn't hydroscopic, so as long as you have no leaks there is no reason to bleed let alone flush.
The only reason to flush is if you're getting inconsistencies in feel or bite point. This can be caused by water in there or corrosion causing the fluid to go black. If it's corrosion then they're on their way out anyway.
Mineral oil isn’t hydroscopic, so as long as you have no leaks there is no reason to bleed let alone flush.
True, but the water that does get past the seals (because some does) sits at the low point of the system in the callipers and boils far more readily than the wet boiling point of DOT.
Also, mineral oil degrades over time and under thermal stress, losing some of its useful characteristics as it goes.
Not only but also, but all my shimano brakes, dating back to first gen twin pots run dirty. My last m785s and current Zees have absolutely filthy oil to the point of total opacity within 6 months. Most of this seems to arise from the lever. Since I dont want the sediment to accumulate around the piston bore, I purge mine from the caliper to the funnel until it runs clear, then bleed as per shimano instructions.
I have some 1998 XT's that have never been re bled at all. No problems with them.
+1 the Marshy, Syndicate "bleed" method 👌
