M20K Rocket Brake Issue (Master cylinder)

[Austin305Rocket]

Just curious if there's other Rocket owners out there that have had to replace the brake master cylinder?

We've had an ongoing issue with ours - had a couple reseals and bleeds and we keep having the issue.  It's a dangerous issue as you can see - once there's no pressure the rudder pedal actually flips over when applying brake pressure to the top of the pedal.

Our mechanic came to check it out and seems there are numerous variations of the part under the same part number.  

He's going to try replacing the stat-o-seal again.  It seems that mfg tolerances vary and so a different one 'may' fix the issue and keep us from having to spend $800-$1k on a new master cylinder.

Ours is a 1982 model M20K with the Rocket conversion.

Thanks in advance!

[1980Mooney]

I don't believe that Rocket Engineering altered the brakes or master cylinders on the Rocket or Missile Conversions.  I owned my 1980 J when converted to a Missile and there was no change during the conversion.  Looking at the Parts Diagrams it appears that the master cylinder on a 1982 K is the same as the master cylinder on the J models from 24-0764 - 24-2999 (1978 - 1990).  They are the "small capacity" Parker Hannifin.   Therefore you simply have brake issues that are the same as any other K and Mid-body of that vintage. 

[Fly Boomer]

1 hour ago, Austin305Rocket said:

We've had an ongoing issue with ours - had a couple reseals and bleeds and we keep having the issue.  It's a dangerous issue as you can see - once there's no pressure the rudder pedal actually flips over when applying brake pressure to the top of the pedal.

That doesn't look good.  I would like to know the solution when you figure it out.

[A64Pilot]

I just re-built both my 10-49 master cylinders, it’s just three o-rings and a “statoseal”

My swag is the part on the end of the cylinder that moves back and forth a little as evidenced by the small spring under it is sticking in place or an o-ring is twisted, make sure it’s not on upside down too, the hollow part is for the spring to fit into of course

Part #5 on page 8, the piston

https://www.aircraftsupply.com/pdf-files/Cleveland-Seal-Repair-Kits.pdf

If you have 10-49 master cylinders of course

[1980Mooney]

880027-501.   The large capacity 10-24D can be retrofitted in pairs.  I think that is what is in the "Retrofit Kit"/

 

[Fly Boomer]

Advantage to large capacity?  What would I get for my money?

[1980Mooney]

1 hour ago, A64Pilot said:

I just re-built both my 10-49 master cylinders, it’s just three o-rings and a “statoseal”

My swag is the part on the end of the cylinder that moves back and forth a little as evidenced by the small spring under it is sticking in place or an o-ring is twisted, make sure it’s not on upside down too, the hollow part is for the spring to fit into of course

Part #5 on page 8, the piston

https://www.aircraftsupply.com/pdf-files/Cleveland-Seal-Repair-Kits.pdf

If you have 10-49 master cylinders of course

I think the 10-49 and 880027-501 are the same based upon the compatibility of this kit:

Brake, Master Cylinder Kit. Mooney M20J With 880027-501 / A-110-37 / 10-49 Brakes PPBMC31 - Knots 2U, Ltd.

[1980Mooney]

3 minutes ago, Fly Boomer said:

Advantage to large capacity?  What would I get for my money?

Probably nothing.  Your calipers do the stopping.  They put them in the last K's - the "Encore" in 1997 and '98.  Those planes had a 230 lb. GW increase to 3,130 lbs. and I think they had double puck brake calipers.  They put them on the last J's with single puck calipers from 1993 - '98 but they were only 2,900 lb GW.  I have a 3,200 lb GW with an IO-550 transplant on a J - It has the original brakes (small capacity master and calipers).  It stops adequately.

[A64Pilot]

24 minutes ago, 1980Mooney said:

I think the 10-49 and 880027-501 are the same based upon the compatibility of this kit:

Brake, Master Cylinder Kit. Mooney M20J With 880027-501 / A-110-37 / 10-49 Brakes PPBMC31 - Knots 2U, Ltd.

The overhaul kit for the 10-49 apparently lists several master cylinders, ones I got from Spruce did not list the 10-49, but the O-rings and stat-o-seal fit.

The Orings are about $1.50 ea, the kit is $40, but the only way I saw to get the Stat-O-seal.

The rubber parts on mine were 40 yrs old and so hard I had to cut them off, the Stat-O-seals seemed fine as they don’t move against anything, it’s a compressed seal that doesn’t move, but as much trouble as one master cylinder was to remove I didn’t want to risk it, so with shipping and tax I paid darn near $100 for the two kits, but was fine with it as no telling how much longer that Stat-O-Seal will be available.

If I were trying to re-use the Stat-O-Seal, I’d make sure it was covered in hydraulic fluid for removal and probably warm it up with a heat gun so the rubber would be pliable, just warm-ish to the touch, not hot. First one I removed I had cleaned everything with mineral spirits and it was much harder to get it out of its groove, second one I left wet with fluid and it came off easier.

Spruce part

https://www.aircraftspruce.com/catalog/appages/clevelandkit08-00353.php

[kortopates]

I think the 10-49 and 880027-501 are the same based upon the compatibility of this kit:
Brake, Master Cylinder Kit. Mooney M20J With 880027-501 / A-110-37 / 10-49 Brakes PPBMC31 - Knots 2U, Ltd.

The old parker hannifin MC are no longer available and haven’t been for years. These were proprietary to Mooney.
Mooney now uses a different manufacturer and part # for the larger capacity which are the ones used on long bodies. They’re not in the K IPC but going to them requires an additional bell crank so pedal orientation is maintained.
If a older J of early K MC is worn out such that replacing seals doesn’t fix it, I believe the only choice is to go the bigger capacity new ones which are $$.


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[Shadrach]

16 hours ago, A64Pilot said:

The overhaul kit for the 10-49 apparently lists several master cylinders, ones I got from Spruce did not list the 10-49, but the O-rings and stat-o-seal fit.

The Orings are about $1.50 ea, the kit is $40, but the only way I saw to get the Stat-O-seal.

The rubber parts on mine were 40 yrs old and so hard I had to cut them off, the Stat-O-seals seemed fine as they don’t move against anything, it’s a compressed seal that doesn’t move, but as much trouble as one master cylinder was to remove I didn’t want to risk it, so with shipping and tax I paid darn near $100 for the two kits, but was fine with it as no telling how much longer that Stat-O-Seal will be available.

If I were trying to re-use the Stat-O-Seal, I’d make sure it was covered in hydraulic fluid for removal and probably warm it up with a heat gun so the rubber would be pliable, just warm-ish to the touch, not hot. First one I removed I had cleaned everything with mineral spirits and it was much harder to get it out of its groove, second one I left wet with fluid and it came off easier.

Spruce part

https://www.aircraftspruce.com/catalog/appages/clevelandkit08-00353.php

FYI Univair has the kits for $34.87 and the parts can be ordered seperately.

https://www.univair.com/tires-wheels-brakes/view-all/199-51600-cleveland-seal-repair-kit/