bleed brakes

[Paul Eckenroth]

Replaced brake lines at annual. Having hard time getting air out. Hand brake, no toe brakes. Any tips? Thanks, Paul

[Mike Day]

Paul...
The best method is to pump fluid from the caliper up to the reservoir, I had a bad O-ring on my left brake and had to replace it, consiquently had to bleed air out. It will involve getting some sort of pump to move the fluid from the caliper back up to the reservoir, I am assuming its the same as my PA-30, but I used a regular oil can, hardware store type with a flexible spout, to pump the oil from the bleeder at the caliper to the reservoir with a hose connected to the end of the flexible spout. Dont forget to empty the reservoir before it runs over, also I had a bit of trouble the first time getting it to flow, the problem was the brake master cylinder was partially compressed, this is what your brake pedal actuates to move fluid to the caliper, this will prevent fluid flow to the reservoir. This is a pretty easy job and I recommend circulating thru extra fluid by filling the reservoir, emptying it and refilling again. This will get rid of the little bubbles that havent made it out of the system and it will circulate out any crap that might be floating around in the system as well. GOOD LUCK.

Mike

[Alan Cheak]

Paul: I too had a heck of a time with my mechanic bleeding my brakes after I changed the brake lines from the wheels up to the wing. My problem was that there was a pin on the park brake side that was not releasing fluid from one side of the master cylinder. Got the little part from Webco for about a $100.00 bucks. At one point we had a mule on the system with close to 500 psi and could not get the fluid to flow.

I read in the Piper flyer an article concerning how to bleed the brakes on a Piper. This guy hooked up a long piece of clear plastic tubing from the bleeder valve (obviously it must be a tit fit) and ran it back under the wing over the top of the fuselage and back down the window and back into the reseivor. The idea being that any bubbles got trapped at the top of the loop.

My mechanic and I didn't have to use that trick but I thought that was interesting.

Alan Cheak
'63 250

[Paul Eckenroth]

Alan, We are bleeding at each wheel and getting fluid flow that appears bubble free from the resevour. With your pin problem in the P brake, was there no flow at all? Paul

[Alan Cheak]

NONE-NADA-ZIPPO. I guess the problems lies in the master cylinders. I checked with Webco about putting in 2 new M.C. and I believe they wanted something like $1500.00 apiece. WOW.

My park brake has never really worked in the 15 years I've owned my plane. Used it a couple of time when I first got it, and the brakes would sometimes get locked up and not release. Did not want to be on a trip somewhere out there and have that happen. Probably one reason it got gummed up.

But as I said before my mechanic and I had a hydraulic mule on the system and with a lot of pressure we still could not get fluid to flow through the system.

My mechanic says Pipers can be bears while a typical Cessna might take a hour to bleed the system. Its just a PIPER thing.

Alan Cheak

[Paul Eckenroth]

OK, guess we'll bleed bleed bleed. Tech says next step is fill each line, one at a time. We changed all the lines. Inside as well. They were orig. from '59. So, lotsa air.

[DAVEG24]

I'm assuming that you do not have a traditional bleeder screw on your brake assembly. You need to make one. The easy way to make a fitting is to use a 10/24 bolt that will screw into the brake cylinder. Get a 10/24 bolt that isn't threaded all the way. You may have to cut some additional threads, so that the bolt will seat into the housing. Next, drill a small hole through the center of the bolt. If you have access to a lathe or a milling machine, it makes the job easier. Cut off the bolt head and you now have the tool that you need to sucessfully bleed the brakes. Screw it into the brake housing, connect a flexible line to it and a pump containg brake fluid and pump away. An oil pump can will work just fine. Best to start with an empty brake resevoir as it will fill up quickly. After you have filled the resevoir, remove the "tool" and re-insert the screw that seals the system. Check for a good resistance on the hand brake. You should only have to do this once.

Dave Gitelman

[Richard Muller]

Paul,
According to my parts catalog the Cleveland 30-21 Brake Assembly is installed in PA24-180 and PA24-250 upto serial no. 3296.
If this pertains to you see attached a procedure for brake bleeding.

The described procedure is not needed for PA24-260 as they have Cleveland Brake Assembly 30-41 resp. 30-23. These assemblies have internal boreholes on each cavity so that air can escape upwards without removing the assembly.

Richard

[Paul Eckenroth]

Richard, I owe you a cold one.

Paul

[DAVEG24]

The procedure described in the download will only remove air from the brake cylinder. It does not address the problem of air trapped in the lines leading to the brake cylinder. We also do not know that the master cylinder is free from trapped air. The most effective way to purge the system is to push brake fluid from the brake cylinder up through the master cylinder and into the resevoir. The brake cylinder used on the early 180 and 250 did not have a bleed screw that would accomodate the above procedure. I gave you a procedure to make one in a previous post. Take your pick as to what to use. Good luck.

Dave Gitelman

[Wayne Haristy]

While bleeding the brakes on the 1962 Comanche 250 me and my partner are rebuilding, we could not get any fluid to push through on the left side. We were bleeding the brakes from the calipers through the master cylinders into the resevoir. I found that the brake pedal was not quite all the way retracted just by taking your feet off of it. I reached down and pulled the pedal all the way up and my partner was then able to push the fluid through the system.

[DAVEG24]

You might not have a 10/24 bolt laying around, so start with 10/32 and cut a new thread. Continue cutting past the existing thread onto the shaft, as you're going to cut off the part that was originally threaded. As others have stated, if the master cylinder park function is not released, you will not be able to push fluid through the system.

Dave Gitelman

[Paul Eckenroth]

thanks guys. There was air in the calipers and I made a bleed fitting out of a 10/24 bolt. All is well in brakeland.