PA28 brakes weak

[drunkenbeagle]

Both left side cylinders were "resealed". What's you're next move? (This is actually where this started).

"Resealed" just means swapping a few O-rings that were probably fine to begin with. Does not in any way mean the cylinder is good.

 

[drunkenbeagle]

That's right, you're not actually going to fix it, you just want to question me. I'm a better mechanic than you. I've spent the 10,000 hrs and gotten very dirty and sad along the way.

I agree, you definitely got very sad along the way.

Anyway, I'm not a mechanic.

 

[Flied Rice]

We did finally find a little fluid under the L pedal, and a little on the parking brake handle.

 

[trafficinsight]

Does the parking brake apply both wheels?

This is from the deep recesses of my memory but the original cherokees had no toe brakes at all. Just the handbrake. When they added toe brakes they routed everything through the handbrake cylinder so it's between the toe brakes and the brake cylinders. So you have to bleed the handbrake as well as the toe brakes and if a seal in the hand brake is gone you may get these symptoms...

I also may have missed it but don't see where you've checked if the caliper at the wheel needs new seals?

I also second the people say saying follow the lines and look for leaks. I spent all afternoon once trying to get a 182 bled and it'd be good and then 20 minutes later it'd be spongy again... finally found the pinhole seep in the rubber lines beneath the floor.

 

[milleR]

Do both left brake pedals have master cylinders? No, they don't. Your mechanics are taking advantage of your ignorance. Find a new honest mechanic. That hydraulic wheel brake system has been used successfully for decades, if your mechanic can't fix it than they aren't worth what you're paying them. They probably don't want to get dirty.

Okay. I've always said I never worked on airliners or small airplanes. I did work on one small airplane for a little while, eventually the brakes were becoming a very sore spot so we had to come up with a new strategy. We had brilliant people and they did some figuring, engineering and machining and we put T-33 brakes on it. I'm an idiot when it comes to brakes, please educate me.

If that picture gives you a headache than perhaps working on airplanes is not your calling. That's right, you're not actually going to fix it, you just want to question me. I'm a better mechanic than you. I've spent the 10,000 hrs and gotten very dirty and sad along the way. I prefaced what I said about the PA28 brakes with the fact I've never worked on them. I don't care, and neither does @Flied Rice, although I suspect he's entertained by the attack he's seen. My opinion remains the same, find a mechanic that wants to fix things rather than smoking a pencil.

Well, you've perfectly encapsulated the mechanic I don't want working on my plane. A bold statement responded to with a factual contradiction; you asked for clarification and education and when so provided you followed up with a derogatory response. That lack of professionalism is just embarrassing. I wouldn't stand for it in my business and I wouldn't accept it in my mx shop.

 

[Roger Roger]

Does the parking brake apply both wheels?

This is from the deep recesses of my memory but the original cherokees had no toe brakes at all. Just the handbrake. When they added toe brakes they routed everything through the handbrake cylinder so it's between the toe brakes and the brake cylinders. So you have to bleed the handbrake as well as the toe brakes and if a seal in the hand brake is gone you may get these symptoms...

I also may have missed it but don't see where you've checked if the caliper at the wheel needs new seals?

I also second the people say saying follow the lines and look for leaks. I spent all afternoon once trying to get a 182 bled and it'd be good and then 20 minutes later it'd be spongy again... finally found the pinhole seep I'm the rubber lines beneath the floor.

Yeah, your recollection matches mine. I think the original Cherokee stole a bunch of stuff from the Tripacer, which also just had the single hand brake and the overhead crank for the trim.

What I remember, and it’s been the better part of a decade since I touched a Cherokee, is that you had a couple factors that made them such a bitch to bleed.

1. Sheer number of parts in the system. 5 master cylinders vs 2 in, say, a 207, made a lot more places for things to go wrong (although several of ours had no brakes on the copilots side).

2. Use of -4 hose/tubing for brakes vs -3 in similar Cessnas meant you had to move (if I’m mathing right) over twice the volume of fluid to get a good bleed.

3. Arrangement of said 3-5 master cylinders, especially the 5 cylinder setups, meant you could have a stubborn bubble that would just bounce back and forth between sides.

3 (a) the installation of the toe brake cylinders was sort of “upside down” and sometimes you had to take them loose and flip them around to get a stubborn bubble out.

4. The design of the toe cylinders with the parking brake meant that if you had wear on the shaft for the master cylinder, it could suck air in, which then could get pumped into the rest of the system when using the parking brake. The shaft on a Cessna could be worn clean out and it wouldn’t matter with the reservoir being mounted right on it and the different parking brake design.

Your typical SE Cessna brake system is just so much simpler and easier to work with.

Like I said this is just the highlights that I remember. The upshot of it is that ANYWHERE that shows a fluid leak in the system is also a place it could pull air in and you need to start with tracking down and fixing all of those first.

 

[trafficinsight]

If the left toe brake cylinder got resealed I'd be willing to believe that fluid was from removing it.

 

[DE727UPS]

When I taught in a Cherokee I always had the students get used to the hand brake as it often seemed more effective. I swear, after reading this thread, when my toes brakes need work someday, I'll have them taken out and sold on ebay.

 

[trafficinsight]

When I taught in a Cherokee I always had the students get used to the hand brake as it often seemed more effective. I swear, after reading this thread, when my toes brakes need work someday, I'll have them taken out and sold on ebay.

In instructed in an arrow without brakes on the right side, some people were afraid to instruct in it and DPE's wouldn't touch it.

*shrug*