Difficulty Bleeding Brakes Up

[tx_jayhawk]

I'm rebleeding my brakes from the bottom up. On the left side, for some reason, no matter how much pressure is applied, it just "barely pushs the fluid up to the reservoir. It ultimately made it to the top, but then the brakes were still spongy (despite no visible bubbles). Anyone else run into this where the brakes won't bleed up? The right side worked pretty well, but the left really wouldn't. The valve was definitely fully open.

As of now, I don't see any notable bubbles, yet both sides feel spongy yet I cant seems to bleed one side.

Thanks,
Scott

 

[Dbro172]

Reach down in the floor of the cockpit and pull back on the break pedals by hand so they are fully retracted. The slightest depression on these pedals will stop flow

 

[N941WR]

Also, what are you using to push the fluid?

My first pump was a small modified yard sprayer. The problem was that the end of the air pump was in thre brake fluid and when I would pressurize the tank it would pump air into the fluid.

The fix was to get a bigger (taller) tank that moved the end of the pump up, out of the fluid.

 

[Mike S]

Reach down in the floor of the cockpit and pull back on the break pedals by hand so they are fully retracted. The slightest depression on these pedals will stop flow

Pretty sure this will make things better for you.

You might consider doing a little research about adding springs to the master cylinders and maybe long pivot bolts-----all been discussed here many times.

 

[BillL]

Reach down in the floor of the cockpit and pull back on the break pedals by hand so they are fully retracted. The slightest depression on these pedals will stop flow

Yep, probably have partially covered the return hole in the master cylinder. If pulling back does not fix it then you should check, otherwise the line would fill from reservoir.

 

[Berchmans]

What others said

Yep, if the cylinder isn't fully open you will find it hard to push. I used a turkey baster syringe and clear plastic tubing. since everything is clear you can see any air bubbles before they get into the brake system. No spillage at all...

 

[VETE76]

We just used a plastic hypo needle. You can get em at a drug store, they are used to clear ear wax. Plastic tube and filled from bottom up. we did 3 rv7's only one gave us trouble and after we pulled the brakes back they filled fine. no mushy peddles either! worked great. if you assemble the system correctly you wont need return springs. the pivot bolts have to be loose and the peddle has free travel. we had to adjust one of the 3 RV's
now the important thing is check your brake fluid more than once a year. an rv6 didn't, and his leaked down and when he landed he applied brakes and only one grabbed the other side didn't so off the runway, right in to an immovable object. $30,000 later and 1 yr of rebuild............. he wrecked it on 1st flight. he forgot to put the cotter pin in the castle nut holding the throttle cable on. he flew 45 min decided to land and was too fast so he pushed the throttle to full open to go around.....nothing, went off, end hit tall weeds and flipped it. he has now switched his hobby to playing checkers and moved to NC. his wife made sure of that. this guy was a 20 yr military pilot!

 

[rocketbob]

The Matco master cylinders have a return spring internally, so there's no reason to add an external one. Two days ago I bled the brakes in the RV after rebuilding a leaking Matco master cylinder. It was simple. Pull the snap ring, the piston comes out and you replace two o-rings. Bled with my little pump oil can from the bottom up, and I normally run the whole can thru to get all the air bubbles out. I screw a hose fitting to the top of the reservoir and have a hose draining back into the quart of ATF I use.

 

[Tango Mike]

I use a pressurized bottle from Spruce and had variable results until I began using a bungee cord from a pedal on one side around the fuel selector valve to the corresponding pedal on the other side to make sure they are fully aft. It seems that even the slightest depression of the pedal closes the check valve.

At the reservoir end, I use a 90-degree fitting in place of the cap so there's room to screw in a bleed fitting connected to a hose and run that into a water bottle with a little fluid in it. The bubbles are easy to see. With nothing but fluid flowing, switch to the other side and repeat.

 

[tx_jayhawk]

To close the loop on this, it ended up being the pedal was ever so slightly depressed. I grabbed it and snapped it back, and it seemed to bleed OK. Thanks for all the help.

 

[SHORTRV7]

Return Spring on Shaft

Reach down in the floor of the cockpit and pull back on the break pedals by hand so they are fully retracted. The slightest depression on these pedals will stop flow

Does anyone have an example of putting a spring over the shaft of Matco Master Cylinder? After calling Matco they said if the brakes don't fully extend it causes pressure that ultimately causes fluid to leak. Matco also said to be sure and protect the shaft especially an inch of the resivour. I would like to see some examples of this if you have pictures.