Advice on Rebuilding Matco Master Cylinder?

Any advice on rebuilding these things? A couple in my 7A are oozing fluid from the top, giving the insides that manly 5606 odor.

I downloaded a TSB from Matco for the MCMC-4 series which will be helpful but curious about what pitfalls await me while rebuilding.

RVphil said:

Any advice on rebuilding these things? A couple in my 7A are oozing fluid from the top, giving the insides that manly 5606 odor.

I downloaded a TSB from Matco for the MCMC-4 series which will be helpful but curious about what pitfalls await me while rebuilding.

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Just did one a couple weeks ago. Very easy. Hardest part is the final step of compressing the plunger/spring and then getting the snap ring in place. Easy if you have a short piece of aluminum tube that has inside diameter slightly larger than the shaft and outside diameter smaller the the inside diameter of the snap ring. Just put it over the shaft and push down to get all the guts inside then snap the snap ring in.

Of coarse then you need to decide if you are going to do the SL-00047 to replace the 5606 with 83282. Then you find the suggested low temp Viton o-ring at vans is back ordered so you you need to decide if you want to use the McMaster-Carr not-quite-so low temp Viton o-ring.

Brake cylinder

Will the tube method work on the Bendix? I have to do mine next week. I have both fluids in mine over the years, doesn’t seem to matter. Anyone know the size plug you need to block the fluid from coming out? Thanks!

RVphil said:

Any advice on rebuilding these things? A couple in my 7A are oozing fluid from the top, giving the insides that manly 5606 odor.

I downloaded a TSB from Matco for the MCMC-4 series which will be helpful but curious about what pitfalls await me while rebuilding.

Click to expand...

Oozing from the top may be a symptom of side loading on the cylinder. Ask George at Matco about side loading. It will be an interesting conversation.

Basically the cylinder is not moving straight up and down. It’s usually caused by the rudder pedal frame not being square. I had on cylinder that I had to add a couple washers to fix that problem.

When you take the cylinder a part, you’ll see the issue. There is a oring that wears more on one side, which enables the oozing.

I also added return springs while I had everything a part.

The upgrade is pretty easy. When I ordered the last set a few years ago, they were a little less expensive at ACS than Matco. I don’t know if that is still true.

Don't believe the leaks are from side loading and will check for proper geometry while the cylinders are off. Several searches on this topic revealed side loading issues, but the leaky ones are on the pilot left side and passenger left side. My copilot wife never touches the right side pedals and most of my braking bias is on the right due to the 390 up front.

rleffler said:

Oozing from the top may be a symptom of side loading on the cylinder. Ask George at Matco about side loading. It will be an interesting conversation.

Basically the cylinder is not moving straight up and down. It’s usually caused by the rudder pedal frame not being square. I had on cylinder that I had to add a couple washers to fix that problem.

When you take the cylinder a part, you’ll see the issue. There is a oring that wears more on one side, which enables the oozing.

Click to expand...

I had side load wear on mine with a few scratches on the shaft, scratches probably caused my leak. Lightly buffed out the scratches and added a washer to get better alignment.

rleffler said:

I also added return springs while I had everything a part.

The upgrade is pretty easy. When I ordered the last set a few years ago, they were a little less expensive at ACS than Matco. I don’t know if that is still true.

Click to expand...

I ran across a few return spring posts from over a decade ago and would like to add them to the master cylinders. I take it the copilot side will need them as well, correct?

And if you have any questions or concerns when you get into it, call George at Matco Landing Systems (their new name). His expertise and customer service is second to none IMO. Good luck

I just rebuilt my left master cylinder a month ago. You'll need internal snap ring pliers and a bench vise with aluminum jaws. The aluminum tube used when reassembling is certainly a good idea.
Deburr any sharp corners with Scotchbrite. Download and print the assembly drawings from Matco's web site for reference.

I believe the side load is inherent in the design of the rudder pedals. It can be improved “side to side” but not “fore and aft”.
My Bucker was converted to hydraulic brakes and has the same rudder pedal mounted cylinders. However, the actuator design operates in a more linear fashion reducing if not eliminating side loading.

Got an email back from George this morning. He gave me a part number for the rebuild kit (MCMCRBD4) and noted my setup has the side loading issue and scored shafts. I didn't feel any unusual wear on them but will pull the pilot sides this afternoon for a closer look.