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Adding brake fluid


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Reservoir is under the pilot side avionics panel in front of the wind screen. 

This reservoir is shared between the brakes and flaps, with the brake line being lower. If your hydraulic fluid is low you will lose flaps first so unless you are also having a flap problem I wouldn't think adding fluid will solve a brake issue.

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32 minutes ago, outermarker said:

I have a '65E that has a soft brake. I want to add some fluid. How do I do this? 

The master cylinder in my C is behind my rudder pedals, up high. Remove the outside panel between the windshield and cowl, it should be there. If you don't have this panel, you'll need a way to lay on the floor and squirt the fluid up . . . My 201 windshield has small panels in front, they are large enough.

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"Soft brake"?

That can be air trapped in the line, or it can be a lack of fluid.  Lack of fluid may affect both sides.

If it's air, you need to bleed the brakes...pretty much like brakes on an old tractor.

Fluid is best added from below at the brake calpher.  I use a big syringe, but there are lots of options.  If you're sure there's  no air in the line you  can just top off the reservoir.

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Follow the advice given so far, above...

Then search for the key words like pressure pot and brake lines and flushing...

pilots with knowledge, find flushing the lines uses gravity to their favor.  Pushing bubbles up from the bottom, suddenly makes sense...

Then you can read some more and find the unusual things like master cylinder wear, chrome coating and things like that.

PP thoughts only, stuff I read on MS...

Best regards,

-a-

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BTW I assume you have the hydraulic flap system?  If there's not enough fluid in the hydraulic reservoir mentioned above, then that system goes soft first before brakes are affected - the flap system takeoff from the reservoir is half way up to give you warning before the reservoir is empty enough to affect the brakes, which are fed from the very bottom of the reservoir - a smart design. It's good to know how to access and top off that reservoir - it should go down minimally over time if the system is tight.  Here's the service manual for your bird - a '65E?

 

Service Manual 1967.pdf

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As with the Facebook post I'm going to say that just bleeding the brakes is a dangerous approach. If you've lost so much fluid air has gotten in since it was presumably checked at annual you have a serious problem that needs to be fixed; not just bleed to make the symptom go away.

 

-Robert

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A couple of thoughts-

You are looking at a problem that has a slim chance of cure by just adding fluid. You need to find where it is leaking from.

Look at the bottom of each wheel cylinder to see if it is wet there with red fluid. Most likely case.

Check your log book and see how long it has been since the wheel brake cylinders have been off and disassembled. Our wheel cylinders have a habit of having the fluid turn to red jelly after many years of sitting in place. Have seen several like this. 

Do you have copilot brakes? This more than doubles your work to bleed the brakes.

You might be loosing fluid inside the cabin in front of your pilot pedals from the parking brake valve. Check that out. 

Check the panels outside under your foot wells to see if the brake master cylinders themselves are leaking. They will be wet with red fluid. 

One unchecked item is the fluid feed line from the fluid can to the flap pump to the flap cylinder. I'll bet if is 1965 material. I've had them leaking. 

Check the flap cylinder bottom center panel for leaking. You'll see leaks flowing from the panel seams.   

You have to find the leak to cure the problem.  

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Check the logs...

If the low pressure hydraulic return lines haven't been changed... they are very likely to be old, swollen, hard, crusty, cracked, and leaking...

When this happens, red oil drips onto the belly panel and dirt cakes on top of that...

So I have heard... about '65Cs... :)

PP thoughts only,

Not a mechanic.

Best regards,

-a-

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BTW: Some have reported problems getting the last bit of air out of the system after replacing the orings in the master cylinder. A reported solution that several have reported success with is to pull into a steep climb and tap the brakes. Not needed to try it myself; just passing this along.

 

-Robert

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