Master Brake Cylinders

[gliderman]

I have removed my rudder pedals and master brake cylinders with the need to do some re-work on the pedal pivot pin holes that are elongated and also to see what can be done with the MBC that seem to leak constantly (the right one more that the left) The part number that is visible on a paper decal on the MBC is 0541138-838. I cannot find any info on the -838 as to overhaul parts and seals etc. As the decal is somewhat faded it is possible that this is not a correct number but under a bright light it does seem to suggest that it is a -838.

Anyone with any info on this one.

Thanks,

Mike

[n2582d]

Mike, You'll find some good advice on repairing your rudder pedals here. Especially note sfarringer's repair. Here I noted that Air Repair has new pedals available for $79. Generally, master cylinders are rebuildable. Yours are the wrong p/n but without the drawings it's hard to know if it's a minor difference such as the finish or a major difference such as the stroke or attachment hole diameter. You'll find the correct p/n's in this discussion. You'll also find a lot of moderately priced master cylinders on online auction sites but it may be a challenge getting the correct p/n.

[gliderman]

Mike, You'll find some good advice on repairing your rudder pedals here. Especially note sfarringer's repair. Here I noted that Air Repair has new pedals available for $79. Generally, master cylinders are rebuildable. Yours are the wrong p/n but without the drawings it's hard to know if it's a minor difference such as the finish or a major difference such as the stroke or attachment hole diameter. You'll find the correct p/n's in this discussion. You'll also find a lot of moderately priced master cylinders on online auction sites but it may be a challenge getting the correct p/n.

Hi Gary, thanks for the response. I did see the repair thread for the pedals and will do something similar with mine. I have scoured the internet to try and find part numbers for my cylinders so as to order up the seals but have had no luck. The search will continue and as it is now getting down to the minus temps here in Canada no real rush to complete the project. Cheers, mike

[n2582d]

Seal Kit

... also to see what can be done with the MBC that seem to leak constantly... .

...it is now getting down to the minus temps here in Canada ... .

Maybe there's a connection. Remember January 28, 1986? Stay away from Viton o-rings on your MBC rebuild.
Stay warm up there!

[gliderman]

Seal Kit

... also to see what can be done with the MBC that seem to leak constantly... .

...it is now getting down to the minus temps here in Canada ... .

Maybe there's a connection. Remember January 28, 1986? Stay away from Viton o-rings on your MBC rebuild.
Stay warm up there!

I recall that day very clearly. Doubt if a failure on my seals on a MBC would have the same consequences however.

[n2582d]

Mike, I link I sent for the o-rings from Sky Geek is a McFarlane Aviation p/n who gets their seal kit from Trimcraft. It might be worth calling them for their price on the kit. But really the only o-rings you need to rebuild your master cylinders are two Lock-O-Seals, p/n 800-001-6, (formerly p/n 200 AC-6) and two piston o-rings, p/n MS28775-110, (formerly p/n AN6227-8). For US $15.46 you can get them from Univair. They're available cheaper elsewhere at places like Yingling Aviation but they have a minimum quantity purchase requirement. Anyway, good luck on the rebuild.

Click to Enlarge

[sreeves]

I was just looking at McFarland regarding the brake and master cylinder seal kit. The eligibility list shows the 170B but not the A model. Is there a difference between the brake master cylinders on the B vs A?

[Bruce Fenstermacher]

The smooth shaft version lever slides up the shaft to engage.

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Yes. From 18000-19200 they used part 04811058. There are two types of plungers in these cylinders, a serrated shaft and the smooth shaft. The serrated shaft was suppose to have been replace because the shafts might break on the serrating. I still have these installed in my A model. The serrations where for the parking brake lever which slide into the slots holding the plunger. The bad news is these shafts might break. The good news is the parking brake, being totally different than later versions can not be accidentally engaged.

The parking brake lever is moved into the shaft to engage it, not slide up the shaft like all others.

The replacement shaft for the serrated was smooth and required a different type parking brake lever that was pulled up the shaft and jammed the shaft, holding it in place when engaged. This type arrangement can possibly be accidentally engaged by hitting the firewall but it depends on rotation. The lever is not as prominent and less likely to be accidentally engaged by the firewall.

The smooth shaft version lever slides up the shaft to engage.

Screen Shot 2016-11-03 at 7.44.00 AM.png (49.32 KiB) Viewed 29694 times

This early master cylinder has one simple o-ring, a AN6227-7, no matter what plunger shaft you have.

Starting with the B model 20267 to 24999 was a different master cylinder. After 24999 was a different part number but I think the basic cylinder and parts the same. This cylinder has a parking brake lever that is also pulled up the shaft to jam the plunger in place when engaged. It is the most susceptible to being accidentally engaged by the fire wall.

The B model version with the brake lever that slides up the shaft to engage. Note the difference between it's construction and that of the early A models for identification.

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This master cylinder has a Lock-o-Seal # 200AC-6, an AN6227-8 and that is it.

Lock-O-Seals have other names like Stat-O-Seal. There is also a MS and NAS equivalent.
When searching for Lock-o-Seal 200AC-6, 800-001-6 comes up most often.
Most of the 800-001-6 seals I found where in the $6.50 range.
If you search Aircraft Spruce for 800-001-6 or Lock-o-seal 200AC-6 you get STAT-O-SEAL NAS1523-8B for $2.45
You will need an AN6227-8 or MS28775-110 as well for the B model for about 50 cents.
(MacFarlene sells the kit CBS-KT-1 for $9.68 which I presume has both)

If you have the early A model master cylinder you are only looking for an AN6227-7 or MS28775-12 for less that 50 cents.

BTW it seems the seals are changing depending on what you get it might not match what you had. Lock-o-seals traditionally where a washer with an o-ring sort of crimped inside. The Stat-o-Seal and NAS pictures I saw look the same. The MS 800-001-6 is two parts. A washer and an o-ring that fits inside.

Pictures from Parker's site.

Traditional Lock-O-Seal

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800-001-6

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And one last important thing. Many early 170s had their master cylinders changed out to later B model versions OR other master cylinders from Cleveland and Scott. You need to identify what you have.

[sreeves]

Thanks Bruce. My 170A is serial number 20216. That makes it one of the last "A"s made. So I guess it should have the old master cylinder, but it doesn't. It must have been changed out (not in logs) to the "B" model type as that is what I have. So I'll try McFarland for the kit. Thanks for the info.

[c170b53]

Like Aryara, I took apart my master cylinder. I had removed it only for access to replace a skin. At first I thought I'd skip taking it apart but thinking that it too might be full of crud I investigated. And it did have a whack of crud but also it also had a plug from the filling port that had fallen inside. That plug had been there sometime before I bought the plane in 95 .
Now removing the inboard side just to see what's inside

[MoonlightVFR]

Just finished both master cylinders C170B sn 26433 1954.

Did not have a McIntosh surprise. Wow, a plug down inside the reservoir!

Spent way,way too much time studying operation of unique brake master cylinder.

Now have great respect for the thoughtful engineering in the combination reservoir/master brake cylinder. There is crud in bottom of these 60 year + cylinders. Very bottom of cylinder allows residue from tiny 0 rings
to accumulate below were the hydraulic fluid is pushed down to brake pucks.Containment. Use Q tips or a tampon to remove residue.

You do not have to remove master brake cylinder to do a complete job.

[c170b53]

Took the other brake cylinder apart and yep I'm two for two, it's the same type of plug I found in the first cylinder I took apart. Amazing the amount of goo that was also in the bottom, if it's been awhile for your master cylinders, it might be an idea to have a look as it's not a terrible job.

[johneeb]

Jim, is there a vent hole through the center of the plugs you found inside your master cylinders?

[c170b53]

No, no holes in them. The other thing I found was the compensating sleeve (item 16) outside diameter surface was rough. I polished the roughness out, maybe it will compensate better now although I have no idea what it's compensating for other than possibly my poor piloting techniques. Then again maybe it won't compensate at all so fair warning to all; don't hang close to the runway if you know I'm coming in

[170C]

Source for master brake fluid reservoir filler plugs? Tried checking Spruce but couldn't come up with the correct wording the online search needed.