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Matco Brake Master Cylinder

gblwy

gblwy

Well Known Member
After lots of investigation I am still plagued with brake problems. After resealing everything with Loctite 567, the problem seems to be confined to the right brake on the co-pilot side. This fades rapidy after bleeding, then minimal use (on the ground). No fluid leaks, but somehow air is getting into the system.

With significant difficulty I have managed to remove the master cyclinder and have asked Vans for advice. I don't know how I am going to reinstall a replacement/repaired unit without removing the whole brake pedal assembly.

Looking elsewhere in the forum, I see builders of other Vans models have also had difficulties with Matco units. Matco does provide product assembly details on their website. Anyone experienced problems with RV-12 brakes? If so, how did you solve?

Thanks...Keith
 
Hey Keith

Just a wild guess. Have you double-checked the hose routing ? If you are POSITIVE the hoses go to the correct place, re-bleed it. Are you pushing fluid from the wheel up ?

John Bender
 
Checked

Yes, I checked the routing, and yes I am bleeding from the wheel up. After bleeding there's no bubbles and no leaks.

After taxying around (or just pumping the brakes in the hangar) there's still no leaks but the co-pilot right brake pedal has gone completely soft and the pilot side right-hand brake is slightly less effective.

Cheers...Keith
 
Keith,

I have had this on other airplanes, notably my Piper Arrow. It is almost certainly air somewhere in the system. I would drain the right side and repeat the fill procedure. Sometimes it takes several tries to get the air out. I'll be filling the system on my '12 sometime in the next couple of days. I'll let you know how it goes.

John
 
Are you using the Van's supplied brake line and fitting. I know of a few friends that had issue with those lines and for that reason I used the Bonaco hoses. I have worked on my brakes a few times and each time I push the fluid from the wheel side to the top and this method required almost no bleeding.
 
Yup, I'm using standard Van's supplied stuff.

I have done the brakes perhaps 5-6 times now. The brake lines are all visible from the tunnel up to the reservoir. After bleeding there's no visible air in the lines. The right wheel brake works initially from either seat, so I don't think there can be air in either master cylinder or between the wheel and the first cylinder. It looks like air is being introduced at the second cylinder as this pedal is pumped.

Cheers...Keith
 
Hey Keith

Just another "make work" type idea. Move the cyl in question to a new position ( other side or such ), and see if the problem goes with it. You may have a bad brake cyl.

John Bender
 
And there I was, in your shoes

I had a similar problem once coupled with a little leak. I took the cylinder out and ran a tap into the 1/8" NPT holes. The holes in the matco cylinders are not round as determined by the material removed by the tap. However they are making them,l I suspect tapping instead of thread milling they seam to be getting some deflection.

give it a try.
 
Air in the master cylinder

I experienced a very similar prob when I did my brakes. A couple of the master cylinders had a tendency to "hold" air. Once I pumped all the air out (from the bottom up), once I used the brakes on the those cylinders, air would show up.

What I found was that the air is somehow trapped in the cylinder. The solution that I discovered is to "tap" (repeatedly) the brake pedal while your helper is pumping fluid. This process caused the air to be dislodged....and then could be pumped out.
Worked for me, hope it helps!
 
My Matco "problem"

I recently attempted to do my first taxi test and noticed that the pilot's right brake pedal depressed all the way to the firewall. When I got the airplane in the hanger and examined the brake system, I had a lot of air in the lines for the right brake system. When I attempted to refill the brake fluid from the bottom up, I could not push any fluid through the system without using a tremdous amount of force. I track down the location of this blockage and it was in the pilot's side right master cylinder. I removed it tried to take the cylinder apart but it was stuck. There was nothing that I could do to take it apart. Depressing the cylinder to check operation just didn't feel right. It wasn't a smooth travel, but instead kind of scratchy and graby. I contacted Matco and arranged to return the cylinder.

I called Matco today and asked what was their findings (they have had it for four business days) and I was told by the receptionist that I would "have to wait my turn" and the man in charge (George) was on another line. I asked for George to call me. The lady later returned the call to me and stated that "the owner is out of town and he wants to look at the cylinder and he'll be back tomorrow." Real good customer service!

When I find out exactly what happen to the cylinder, I will pass it along.

Hopefully, I will receive my master cylinder back soon so I can continue to get ready for my first flight.
 
Problem found

I received a call today from Matco (George) and he gave me their findings. My problem was a manufacturing defect on the inside of the bore. This caused friction during the operation of the cylinder and led to a partial failure of components on the shaft. A new cylinder will be shipped out to me today. This was good follow-up service provided by Matco.
 
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