Brake Cylinder Problem

ebyars · #1 12-03-2018, 06:36 AM

I have a brake cylinder that is leaking fluid inside the cockpit. I removed all four cylinders and replaced the seals. One of the cylinders is still leaking fluid. I think this one was responsible for the main leak that I had initially. Should I just buy a new master cylinder. It is a Cleveland 10-30 master cylinder. Or is there something else that I can do to stop the leak besides the rubber seals that I already replaced?

Thanks,

Raymo · #2 12-03-2018, 08:26 AM

Replacing the seals/o-rings should fix the leak. If not, it is likely corroded and may need to be replaced.

rocketbob · #3 12-03-2018, 09:15 AM

You have to polish the inner bore and shaft to a mirror finish. I typically use progressive grades of wet/dry sandpaper and light oil up to 800 grit. Split a wooden dowel with a bandsaw and cut the sandpaper into rectangular strips about 2" long. Chuck the dowel in a drill. If you don't have access to a lathe you can use the drill to polish the shaft.

Malndi · #4 12-03-2018, 12:56 PM

What Bob said. When rebuilding the Cleveland 10-30 master cylinders in my 6 I discovered the piston shafts worn where the top seal makes contact, which was the cause of my leaks. After polishing out the surface irregularities on the piston shaft and installing new seals they remain leak-free after two years.

airguy · #5 12-03-2018, 02:36 PM

Don't automatically assume the master cylinder is leaking just because you have fluid in the cockpit. It's the most likely path, true, but I had a situation on my 9A where I had an air bubble in the line and had the reservoir completely full - and every time I climbed up high (mid to high teens) it would burp out a few drops. The fluid will come down the line from the reservoir all the way to the connection at the master cylinder and drip on the floor - looking for all the world like a cylinder leak. Took me quite a while to figure it out and purge all the bubbles out, and started keeping the reservoir just 3/4 full, then just like magic no more leaks...

I didn't identify the real culprit until trying to clean up fluid one day with some ultra-cheap paper towels that were thin enough to read through - I ran one down the line from the reservoir and it came off visibly wet - but you couldn't see it on the line in low light and a good paper towel might not have showed up. Try using a coffee filter or plain white paper on that upper line to see if it's wet.

ebyars · #6 12-03-2018, 04:09 PM

Does anyone know if the Matco master cylinders that Van's is currently selling are a direct replacement for the Cleveland 10-30 that I have?

rocketbob · #7 12-03-2018, 06:07 PM

I have not had good luck with Matco masters with Cleveland brakes. Ratio is wrong. They also will leak. Grove makes a master cylinder with a higher surface area ratio that works better.

ebyars · #8 12-03-2018, 06:37 PM

Just my luck, I just ordered the Matcos from Vans. You are going to love your Rocket! A friend of mine has one and its a Blast!

JonJay · #9 12-04-2018, 10:33 AM

Quote:

Originally Posted by rocketbob

I have not had good luck with Matco masters with Cleveland brakes. Ratio is wrong. They also will leak. Grove makes a master cylinder with a higher surface area ratio that works better.

Interesting.
That is, or was, the Vans standard, and I assume what most of us are running.
I have only had one cylinder leak at about 700 hours. The cause was obvious as the push rods where scored which is very typical with Vans poor design putting side load on them. Got the rebuild kit and new push rods and all is good, but you can't change the geometry of the Vans brake pedals. They will score and leak again.

Are the Grove seals and/or design more robust? They will be under the same side load.

Infopipe · #10 11-07-2019, 08:26 AM

I've got seepage on one of the Cleveland brake cylinders of my RV6a. I've ordered the rebuild kit from Van's. The Cleveland rebuild instructions say: The installation of O-ring (9) to the piston rod (3), (3A), or (3C) must be accomplished with the aid of an installation bullet (see Figure 3).

Is that really needed?

I've got the floor mount rudder pedals and the right brake has gotten really sensitive. I've skidded a flat spot on my right tire. Do the springs weaken enough to cause this on a Cleveland 10-30 cylinder?

Thanks

Darrell