Bled brakes feel so good

[RobertGary1]

Funny how the small things mater. For the last year or so my brakes had felt a bit hard and seemed to disengage a bit sluggishly. During annual I opened the bleed nipples at the calipers and nothing came out. So I pumped the brakes a bit partially to see what came out but also to clear any debris in the nipple itself. What came out was very similar to the aeroshell 6 I was using. Very thick and sticky. 

Bleeding was trivial. Picked up an oil can at the auto parts store with a hand pump on it and some clear plastic tubing so I could verify no air in the line. Then I just pumped 30-40 pumps of MIL spec up the caliper (draining the reservoir a few times to get the old stuff out). 

Now the brakes feel nice a crisp. If it wasn't for the fact that I fly several different planes I might not have noticed the issue but now that I've bled them it's night and day. Only regret is that if I'd planned it better I'd have ordered replacement flex line to replace at the same time  

 

-Robert 

[Stephen Skinner]

Nice Job, I replaced my flex lines a few months ago and they feel a bit spongy. I will try to bleed them again. When we bled the brakes we pumped fluid up to the reservoir.

What is the best method? Since the bleed screw is at the bottom of the caliper, do you pull the break fluid down, pump the breaks to push the fluid down, or as I did pump fresh fluid up?

Steve

[MooneyMitch]

"or as I did pump fresh fluid up? "............. Yes!!

[RobertGary1]

3 minutes ago, Stephen Skinner said:

Nice Job, I replaced my flex lines a few months ago and they feel a bit spongy. I will try to bleed them again. When we bled the brakes we pumped fluid up to the reservoir.

What is the best method? Since the bleed screw is at the bottom of the caliper, do you pull the break fluid down, pump the breaks to push the fluid down, or as I did pump fresh fluid up?

Steve

You need to do as you did, push the fluid up. Unlike cars the bleed nipple is at a low point as you say so pushing fluid down or suction bleeding allows an air pocket to remain in the caliper. Be sure there is no air in the line you are using to push fluid up. I used a clear plastic tube from the pump and ensured the fluid was spilling out the top before putting it on the nipple.

I little bush trick. If you have trouble with air in the line pull up into a steep climb and pump the brakes several times. That often will push air up through the reservoir. 

-Robert

[EricJ]

FWIW, in a car the downside of flushing from the bottom up is that any debris or gook or sludge that has settled at the bottom in the calipers gets potentially shoved up into the master cylinder where it can do more damage than it can in the caliper.   For this reason many people prefer to fill the master and bleed out the caliper, so that the settled crud goes out with it.    It's probably not as big of an issue on airplanes, but overheated brakes can change the chemistry of the fluid in the calipers, especially if the fluid has absorbed any water (which is normal for it to do over time), so getting that fluid out of the system first is also advantageous in a car/truck rather than pushing it up into the master cylinder.   Sometimes a spongy pedal is from overheated or wet fluid that just needs to be flushed out.

The main downside of flushing from the top down is to make certain the MC never gets empty so that air doesn't get in it. 

Again, just automotive experience but it's what I think of when people talk about flushing from the bottom up.

Edit:   Ah, just saw Robert's post about the nipples being on the bottom.   That makes a difference, so feel free to ignore me. 

 

Edited April 25, 2017 by EricJ

[Yetti]

I suck it through from the top then oil can up from the bottom. One of the big turkey flavor syringes to remove fluid from resivoir

[buddy]

I don't know what it is with Mooney's but you should flush out the old brake fluid at least once every 2 years and you won't have a problem.

[RobertGary1]

23 minutes ago, Yetti said:

I suck it through from the top then oil can up from the bottom. One of the big turkey flavor syringes to remove fluid from resivoir

I had to use a flexible pump. At least for me the access panel was not well aligned with the top of the reservoir so you needed to make a pretty tight turn from the access panel to get to the bottom of the reservoir.

 

-Robert