Brakes

[LANCECASPER]

Thanks to Mooneyspace for the Acclaim-specific section!

On the new-to-me Acclaim during the August 2021 annual the non-MSC shop that did the annual “replaced the seals in the left master cylinder”. I have dual brakes (pilot and co-pilot). The left brake on the pilot side is virtually non-existent. The shop never got it right. The co-pilot’s side feel ok.

Any tips or tricks on bleeding to get the left brake back up?

[LANCECASPER]

Follow up on this. I had a couple of well-respected mechanics bleed the brakes and they were slightly better, but the left brake pedal on the pilot's side was still very soft; While at Mooney in Kerrville for the software update they offered to look at the brakes. After bleeding it is much better, I'd say 95%. They mentioned that the pedals also need to be adjusted a little, which required that it be done from underneath. So next time it's in, I'll have that done.

[StevenL757]

1 hour ago, LANCECASPER said:

Follow up on this. I had a couple of well-respected mechanics bleed the brakes and they were slightly better, but the left brake pedal on the pilot's side was still very soft; While at Mooney in Kerrville for the software update they offered to look at the brakes. After bleeding it is much better, I'd say 95%. They mentioned that the pedals also need to be adjusted a little, which required that it be done from underneath. So next time it's in, I'll have that done.

I would have Brian put eyes on this to cross-check the work when you’re in San Marcos when you’re having him look at your G1000 issues.

[LANCECASPER]

25 minutes ago, StevenL757 said:

I would have Brian put eyes on this to cross-check the work when you’re in San Marcos when you’re having him look at your G1000 issues.

Yes I’m going to. The G1000 seems fine now, but I do want to get it over to him . . . Whenever he has the time.  Of course now he’ll be looking at your Ovation soon . . Lol

[StevenL757]

Cool.

Yeah, it should be down there next week.  Trying to work thru logistics.

[LANCECASPER]

To follow up on this, here's what all was done: The brakes were bled by both a MSC which helped, but the pressure bleeder that the Mooney Factory Service Center used was finally successful at getting the softness out of the brakes. They noted that there was still less effectiveness on the left brake. In their defense I just asked them to bleed the brakes.

Within a minute of looking at my left brake Brian Kendrick noticed that the pad was on backwards, so a new disc is in my future. Good news is that my brakes feel like they should.

[Marauder]

Any description what bleeder they used? I had a leak on my left caliper at the annual and the shop replaced the seals. They weren’t able to bleed the brakes afterwards. I ended up loaning them my heavy duty Turkey baster (just a big syringe) which I discovered with my first brake-o-disaster.

I’m convinced that the majority of the issues with bleeding Mooney brakes is the horizontally mounted master cylinders. Air seems to get stuck in there and can be a challenge to get out.


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[StevenL757]

13 minutes ago, LANCECASPER said:

To follow up on this, here's what all was done: The brakes were bled by both a MSC which helped, but the pressure bleeder that the Mooney Factory Service Center used was finally successful at getting the softness out of the brakes. They noted that there was still less effectiveness on the left brake. In their defense I just asked them to bleed the brakes.

Within a minute of looking at my left brake Brian Kendrick noticed that the pad was on backwards, so a new disc is in my future. Good news is that my brakes feel like they should.

One of the many reasons why I continue to go there.  I'll be down there this Friday until Monday working on the airplane, so swing by if you're around.

[LANCECASPER]

1 hour ago, Marauder said:

Any description what bleeder they used? I had a leak on my left caliper at the annual and the shop replaced the seals. They weren’t able to bleed the brakes afterwards. I ended up loaning them my heavy duty Turkey baster (just a big syringe) which I discovered with my first brake-o-disaster.

I’m convinced that the majority of the issues with bleeding Mooney brakes is the horizontally mounted master cylinders. Air seems to get stuck in there and can be a challenge to get out.

I wasn't there when they did it, but it's some type of pressure device. Next time I talk to Mike Kneese I'll ask him.

[Marauder]

I wasn't there when they did it, but it's some type of pressure device. Next time I talk to Mike Kneese I'll ask him.

I went through a bunch of different gizmos. Including this:



I also tried the red oil can gizmo and was able to get to bleed with the marinade injector on the right.




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[Danb]

Just now, Danb said:

10 hours ago, Marauder said:

I went through a bunch of different gizmos. Including this:



I also tried the red oil can gizmo and was able to get to bleed with the marinade injector on the right.




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My brakes over time have needed more force for braking action, wonder what action to take. At last few annuals I mentioned it and was told brakes are ok.

[LANCECASPER]

52 minutes ago, Danb said:

My brakes over time have needed more force for braking action, wonder what action to take. At last few annuals I mentioned it and was told brakes are ok.

Most shops hate to bleed brakes on a Mooney. The ones that have developed a system and know all of the ins and outs don't mind quite as much. The strange and almost humorous thing about it is that each shop seems to have their own way and "this is the only way to do it" and then the next shop has a different way to do it and claims theirs is the only way.

When the Factory Service Center did it in December they just said on the invoice "Bleed brake system IAW Mooney S. M. MAN180 CH 32.". Since it worked so well, I still suspect than a small animal may have sacrificed to the gods of hydraulic fluids before they began the procedure. 

[N201MKTurbo]

I think the problem with Mooney brakes is the lack of vertical travel of the brake lines. On my project Cessna, there is almost 3 feet of vertical distance between the master cylinders and the brake cylinders. This gives the bubbles a reason to migrate to the master cylinders where they can be consumed, or easily blead. 

The vertical distance on the Mooney is about a foot and most of the brake lines are horizontal. The bubbles have no reason to go anywhere.

[Marauder]

My brakes over time have needed more force for braking action, wonder what action to take. At last few annuals I mentioned it and was told brakes are ok.

The reason they probably told you the brakes were ok was because they didn’t want to have deal with bleeding them.

When was the last time they changed out the pads?


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[Shadrach]

23 hours ago, LANCECASPER said:

To follow up on this, here's what all was done: The brakes were bled by both a MSC which helped, but the pressure bleeder that the Mooney Factory Service Center used was finally successful at getting the softness out of the brakes. They noted that there was still less effectiveness on the left brake. In their defense I just asked them to bleed the brakes.

Within a minute of looking at my left brake Brian Kendrick noticed that the pad was on backwards, so a new disc is in my future. Good news is that my brakes feel like they should.

Pad was on backwards??? Please elaborate. Are you saying the backing plate side was facing the disk and the friction material was facing the caliper piston?

[Danb]

21 minutes ago, Marauder said:

The reason they probably told you the brakes were ok was because they didn’t want to have deal with bleeding them.

When was the last time they changed out the pads?


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About 4 years ago.

[LANCECASPER]

8 minutes ago, Shadrach said:

Pad was on backwards??? Please elaborate. Are you saying the backing plate side was facing the disk and the friction material was facing the caliper piston?

Yep, believe it or not.

[Shadrach]

22 hours ago, LANCECASPER said:

Yep, believe it or not.

This was done at an MSC? This is entry level mechanical work and it is inexcusable that a credential maintenance professional or repair station would allow this to happen much less not catch it before it left the shop. The person that did this should not be any when near a wrench.

Edited January 14, 2022 by Shadrach

[LANCECASPER]

10 minutes ago, Shadrach said:

This was done at an MSC? This is entry level mechanical work and it is inexcusable that a credential maintenance professional or repair station would allow this to happen much less not catch it before it left the shop. There person that did this should not be any when near a wrench.

The MSC and the factory were only told to bleed the brakes, so I don't think they ever looked at the pad. I just bought it in November so I can't say for sure but I would guess it happened at the last annual in August (not an MSC and not the most  detailed people I've ever met) and I missed it on the pre-buy, although I caught that the brakes definitely needed to be bled. The shop even mentioned that they tried a lot of things but couldn't get the left brakes to feel right. 

Although the August annual didn't look to be very thorough, in this case I'm glad they didn't go deep into anything. I've been getting some catch-up maintenance done since I bought it. 

[Marauder]

About 4 years ago.

Might be good to ask other Bravo owners what an average life might be. I suspect that the long bodies are harder on the brakes.


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[carusoam]

LBs can be harder on the brakes if you use them….

Changing out the fluid is probably a good idea too…

Probably better to change out some every year…than drain the whole system and fight the bubble challenge…

 

PP thoughts only, not a mechanic…

Best regards,

-a-

[BravoWhiskey]

On 1/13/2022 at 10:02 AM, LANCECASPER said:

Yep, believe it or not.

I have a custom motorcycle... couldn't figure out what was wrong with the front brakes.  Upon closer inspection I realized there were NO pads... just the cylinders eating into the brake disc.  

On the plane I am also having a small brake issue.  The brakes take 3 seconds of continuos pressure to engage and 3 seconds of high power (1250rpm+) to release and start ground roll.  Turns out there is some "jelly" type substance in the line that needs to be bled out.

[N231BN]

I have a custom motorcycle... couldn't figure out what was wrong with the front brakes.  Upon closer inspection I realized there were NO pads... just the cylinders eating into the brake disc.  
On the plane I am also having a small brake issue.  The brakes take 3 seconds of continuos pressure to engage and 3 seconds of high power (1250rpm+) to release and start ground roll.  Turns out there is some "jelly" type substance in the line that needs to be bled out.

That's just 40 year old brake fluid. To do it properly you should also remove the calipers and disassemble, clean, and assemble with new o-rings.

[BravoWhiskey]

10 minutes ago, N231BN said:

16 minutes ago, BravoWhiskey said:

I have a custom motorcycle... couldn't figure out what was wrong with the front brakes.  Upon closer inspection I realized there were NO pads... just the cylinders eating into the brake disc.  
On the plane I am also having a small brake issue.  The brakes take 3 seconds of continuos pressure to engage and 3 seconds of high power (1250rpm+) to release and start ground roll.  Turns out there is some "jelly" type substance in the line that needs to be bled out.

That's just 40 year old brake fluid. To do it properly you should also remove the calipers and disassemble, clean, and assemble with new o-rings.

Its a 17yr old plane... i hope the fluid isnt 40yrs old

[N231BN]

Its a 17yr old plane... i hope the fluid isnt 40yrs old

Ha! That was a little tongue in cheek. I had to flush the brakes on a 2006 Ovation last year so yours is due. The goo in his brakes wouldn't work at all in the winter!

Once it gets that bad you really need to disassemble the calipers to get all of the gunk out. 2hr job max for a decent mechanic.