PA28 brakes weak

[Flied Rice]

2 different mechanics (both AIs) haven't been able to resolve our squishy brakes. The left side keeps needing the line to be bled, but
all that seems to do is bleed me of $$$.
We even had the seal kit replaced on both left pedals, to no avail. Rt side is good.
Have u had this experience b4? Suggestions from those who have actually dealt with it?
Thanks vm.

 

[drunkenbeagle]

2 different mechanics (both AIs) haven't been able to resolve our squishy brakes. The left side keeps needing the line to be bled, but
all that seems to do is bleed me of $$$.
We even had the seal kit replaced on both left pedals, to no avail. Rt side is good.
Have u had this experience b4? Suggestions from those who have actually dealt with it?
Thanks vm.

After getting our brakes resealed 5 or 6 times, did some investigating ourselves. First question is if you are losing any hydraulic fluid. If yes, find the leak. In our case, it was a pinhole in a brake line. 2 person job, pump brakes while using a borescope if necessary to look at every inch of brake line. Took less than an hour for a mechanic to repair the line after we found where the leak was. Will probably require pulling floorboards and/or a bunch of access panels.

We also had a bad master cylinder in one of the pedals. Finding a replacement was fairly cheap. (cheaper than having A&Ps bleed them every week, at least).

 

[Roger Roger]

Good luck, squishy Cherokee brakes have been the bane of many a GA mechanic.

But mostly what @drunkenbeagle said

 

[drunkenbeagle]

Good luck, squishy Cherokee brakes have been the bane of many a GA mechanic.

But mostly what @drunkenbeagle said

Bane of many a GA owner too!

 

[Flied Rice]

Would the affordable first next step be to change out the cylinder on the left pedal, and shud I change out both left sides?
Is the parking brake cylinder any easier to replace or more difficult?

 

[drunkenbeagle]

Would the affordable first next step be to change out the cylinder on the left pedal, and shud I change out both left sides?
Is the parking brake cylinder any easier to replace or more difficult?

Can you be more specific about the problem you are seeing? Is only one pedal spongy, or does it happen on both sides? Does adding hydraulic fluid to the reservoir fix it? Does the brake firm up after you press it a few times? Are you sure there isn't a hydraulic fluid leak? Does bleeding the brake line fix things (it can take 10x longer than you would think it should to get all the air out)?

If it were me, I would start by bleeding the line so the brake works, and keeping track of exactly of where the fluid level in the reservoir was. Then when the problem comes back, see if that level changed.

Disclaimer, I'm not an A&P. Please follow their guidance. You don't need to be an A&P to look for leaks though

 

[Roger Roger]

Would the affordable first next step be to change out the cylinder on the left pedal, and shud I change out both left sides?
Is the parking brake cylinder any easier to replace or more difficult?

As with any tricky problem, you’re going to have more success with a methodical approach to the problem vs throwing parts at it. Doing @drunkenbeagle suggestion of starting with a thorough check for leaks is a good and cheap way to start

 

[Roger Roger]

The other thing I will add along with leaks is many GA airplanes go decades without the flex hoses being replaced, and even if they don’t leak they can become soft and cause problems. If you can’t tell when the flex hoses at the pedals and the landing gear were last replaced, or if it was more than 10-15 years ago, you should replace them all on principle. And look at your flexible engine hoses while you’re at it

 

[Flied Rice]

thanks everyone..appreciate the info.

 

[Flied Rice]

Can you be more specific about the problem you are seeing? Is only one pedal spongy, or does it happen on both sides? Does adding hydraulic fluid to the reservoir fix it? Does the brake firm up after you press it a few times? Are you sure there isn't a hydraulic fluid leak? Does bleeding the brake line fix things (it can take 10x longer than you would think it should to get all the air out)?

If it were me, I would start by bleeding the line so the brake works, and keeping track of exactly of where the fluid level in the reservoir was. Then when the problem comes back, see if that level changed.

Disclaimer, I'm not an A&P. Please follow their guidance. You don't need to be an A&P to look for leaks though

R side is good, on both R pedals.
Lt side presses all the way to the floor on both left pedals. (L brake is bad on pilot and passenger side L brake pedals. R brake is good on both sets of pedals.)
Pumping the parking brake handle had little affect.

 

[Flied Rice]

R side is good, on both R pedals.
Lt side presses all the way to the floor on both left pedals. (L brake is bad on pilot and passenger side L brake pedals. R brake is good on both sets of pedals.)
Pumping the parking brake handle had little affect.

Fluid level was constant

 

[drunkenbeagle]

R side is good, on both R pedals.
Lt side presses all the way to the floor on both left pedals. (L brake is bad on pilot and passenger side L brake pedals. R brake is good on both sets of pedals.)
Pumping the parking brake handle had little affect.

Sounds like air somewhere to me

 

[knot4u]

2 different mechanics (both AIs) haven't been able to resolve our squishy brakes. The left side keeps needing the line to be bled, but
all that seems to do is bleed me of $$$.
We even had the seal kit replaced on both left pedals, to no avail. Rt side is good.
Have u had this experience b4? Suggestions from those who have actually dealt with it?
Thanks vm.

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.

 

[Roger Roger]

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 then they aren't worth what you're paying them. They probably don't want to get dirty.

Most (all?) of the Cherokees with dual brakes have master cylinders on both sets of pedals. But sure, keep spouting off about ignorance

 

[knot4u]

Most (all?) of the Cherokees with dual brakes have master cylinders on both sets of pedals. But sure, keep spouting off about ignorance

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.

 

[drunkenbeagle]

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.

Here's a page from the shop manual for a Cherokee. Like pretty much all GA airplanes, cylinder on every pedal.

Took like 10 seconds to find on google. These things are a pain to troubleshoot, blaming a mechanic you don't know isn't really helping here.

 

[drunkenbeagle]

Lt side presses all the way to the floor on both left pedals. (L brake is bad on pilot and passenger side L brake pedals. R brake is good on both sets of pedals.)

I would suspect the pilot side cylinder if both pedals go to the floor. I think they may be the same part number on Pipers, swapping the left and right side to see if the problem only happens on the right side would be one way to confirm that if so.

Shop manual shows 2 ways to bleed the system (pressure from the bottom, or pumping pedals). Whichever way it was done last time, you might want to try the other way.

 

[knot4u]

Here's a page from the shop manual for a Cherokee. Like pretty much all GA airplanes, cylinder on every pedal.

Took like 10 seconds to find on google. These things are a pain to troubleshoot, blaming a mechanic you don't know isn't really helping here.

View attachment 75602

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.

 

[knot4u]

I would suspect the pilot side cylinder if both pedals go to the floor. I think they may be the same part number on Pipers, swapping the left and right side to see if the problem only happens on the right side would be one way to confirm that if so.

Shop manual shows 2 ways to bleed the system (pressure from the bottom, or pumping pedals). Whichever way it was done last time, you might want to try the other way.

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

 

[Roger Roger]

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.

You spouted your mouth about something you know nothing about and got called out on it, and now instead of eating humble pie you’re being defensive. But oops, you’re not the snowflake here.