Removing forks on bike with Hydraulic disks?

I managed to change my headset bearings without disturbing the brake line. There was enough slack with the bars and stem removed to drop the fork out. Remove your stem, and with a helper as an extra pair of hands, you may be able to do the same.

Failing that, try removing the caliper bolts (especially if the brake line runs down the outside of the fork). With the bars/ stem removed this may give a little more wiggle room. Worth a try before removing the brake line.

PP

You could try removing the shifter from the bars if you'd rather deal with a rewrap than replace fluid 

Whether you need to bleed the brake line will depend on the routing of your brake's hose.

If you are very lucky there may be sufficient slack in the brake line, such that, having undone the stem, you can drop the fork far enough below the head-tube to give enough access the clean / grease the bearings. You can hope!

If the hose routing is external to the fork, you may find that you can unbolt the brake caliper from the fork, if necessary unclipping the hose from any fittings, and then simply remove the fork from the frame to clean bearings etc.. In this case, as you have not disturbed the brake line you should not have to bleed the system, but you may have to realign the caliper with the disk, depending on the fittings you have.

If the brake hose is routed through the fork, then you will probably have to remove the hose from the caliper (and 'unthread' it from the fork itself), or from the brake/shifter on the handlebar (having removed the bar tape and hood, if you have a drop-bar set-up). You should then be able to remove the fork from the frame to clean bearings etc.. In this case when you re-assemble your bike, you will have to reconnect the hose, and then bleed the brake line.

If you do have to remove the hose from the caliper or the brake lever, be careful not to let the hydraulic fluid contaminate the disks or pads. It can help to remove the pads from the calipers, just to be on the safe side. Some brake fluids can damage paint as well, so mop-up as you go....