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RV-3 brake line problem

swjohnsey

Well Known Member
I am the proud new owner of an RV-3 #190/10190 N93JP. It has a brake fluid hemorrhage. I still have brakes so it must be somewhere between the firewall mounted reservoir and the master cylinder on the right side. It has fuselage mounted 24 gallon fuel tank. Will I have to pull the fuel tank to gain access to the brake line. What do I need to replace it with? The current line is some sort of plastic/nylon.
 
Very coincidental

What an interesting coincidence in that my wife's RV-3 just had this exact problem. We would get to the airport and a puddle of brake fluid would be under the center of the plane dripping from the fuel vent. To get behind the firewall required removing the upper skin and windshield (hers is a slider), then remove the fuel tank. Once that's out everything is easy to see and work on. Hers had a loose tee fitting on the back of the reservoir so we just resealed it and tightened it up then bled the system.

To remove the tank, once the skin and windshield are off, you'll need to drain the tank completely, remove the vent line from the front of the tank between it and the firewall, then remove the fuel feed line at the bottom rear of the tank (unless you have an inverted fuel system with a flop tube, which we installed on my wife's plane. In this case the fuel line is located at the front bottom of the tank and will probably require you to lift the tank up and have a helper loosen the line.) Tank should just lift right out. To reinstall, loosen the tank straps slightly to make it easier to get the screws started on the upper skin. You'll have to sit in the seat when it's all back together, reach under the tank, and tighten them back up. They pull the tank up against the skin.

Do any other needed maintenance under there while the tank is out. It's not that hard, but I don't like pulling it unless really necessary. There's great access to everything up front with it out so take the opportunity to look over everything really well. It's a great time to rebuild or replace the brake master cylinders, tidy up wiring, or install any cool avionics. Very easy to get to everything.
 
Thanks! Sound pretty simple. I already have upper skin a windscreen off. Is there a better replacement for the brake line?
 
Replacement

I'm sure if you want to get creative a speed shop could make more robust hoses. Hopefully it's just a simple leak.
 
Reservoir on cylinder

They just screw onto the cylinder with an NPT close nipple.
- Ironflight recommended them to me.
- They have been flawless, easy to fill from the wheel cylinder up, no air- ever.
-Don't be bashful to tighten on the brake pedal cylinder or you will go back to do it after you wipe up the drips.
- TS Flightlines for hoses and firewall bulkhead fittings :)
 
Reservoirs

With a fuselage fuel tank, the master cylinder mounted reservoirs would be a nightmare to service... Can't fathom how you would know when they were full. On the 3A with fuselage tank I would keep the firewall mounted reservoir.
 
The mystery is solved. This RV-3 was built with Gerdes master cylinders that have intragel reseviors. They were connected to another reservoir on the firewall. When I put brake fluid into that reservoir it would fill the Gerdes reservoir to capacity then leak it out the top. Nothing actually wrong with the brakes after I pull the fuel tank.
 
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