What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

RV-8 Brake fluid reservoir

Someone, some where, talked about a better way to do the brake reservoir system for the RV-8. Apparently the stock system can be quite messy and a pain in the butt. Some company sells a better reservoir for this application. Anyone have any ideas ? Cant remember where I saw this .
 
Yes I bought two smaller reservoirs, from aircraft spruce, that screw into the top of each brake master cylinder, works good. You get the advantage of having independent brake system for each wheel. I should have some pics on my build log below.

Bird
 
I did this too and think it is a great way to go. It gets rid of all the tubing. The down side is having to crawl head first into the front cockpit to check levels. I do it when I torque the landing gear bolts during the condition inspection. Since it eliminates leaks you really don't need to access it as often.

I used Grove 067-050 reservoirs. ACS 06-00818
 
Or you could make your own, like this.

Top has a very small breather hole and a nipple with rubber cover. For the initial fill, pump fluid up from caliper. Use nipple for refills.

Tony
 
For the reservoirs, use the Matco clear. Available from Aircraft Spruce. Use a large adel clamp around the reservoir body near the top and another clamp on the braided flex hose and bolt together. This will stabilize the top of the reservoir body and prevent the possibility of rotation. I've had these on my '8 for 12 years. The beauty of this is you can shine a flashlight under the panel and see the fluid level. They also have a higher volume than the aluminum reservoirs. Cheers!!
 
As Rex said, this is the way to go. Here is the aircraft spruce part no. 06-11225 reservoir only & 06-11230 install kit included.

matcobrkfluidres.jpg
 
Any ideas for tall folks?

Yes I bought two smaller reservoirs, from aircraft spruce, that screw into the top of each brake master cylinder, works good. You get the advantage of having independent brake system for each wheel. I should have some pics on my build log below.

Bird

Does anyone have any ideas for putting the individual reservoirs on the side of the actuators (or elsewhere)? I don't have the room for the setup pictured, and I hate Van's tubes and reservoir-on-the-firewall design. Unfortunately, I would hit the bulkhead with the setup you are discussing. Thanks.

-John
 
Brakes

Does anyone have any ideas for putting the individual reservoirs on the side of the actuators (or elsewhere)? I don't have the room for the setup pictured, and I hate Van's tubes and reservoir-on-the-firewall design. Unfortunately, I would hit the bulkhead with the setup you are discussing. Thanks.

-John

Offset the reservoirs using two 1/8 street 90 elbows on each cylinder.
Moves them to the side and allows you to set them level .

I used the alum Grove ones , put an access panel in the baggage floor , six screws and I'm in . I found a zip tie makes a good dip stick , the ridges hold some 5606 .
 
The individual reservoirs are neat and easily accessible when you take out the baggage locker floor.
But I recently had to change from the ground adjustable to the in-flight adjustable pedals to accommodate a taller pilot and found that the reservoirs fouled the firewall at full deflection with the pedals fully forward.
I ended up reverting to the firewall mounted reservoir.

That may not affect your decision, but it's worth a check to see if you have any clearance problems.
 
The only issue I have found with putting the reservoirs on the brake cylinders is that if you over service the fluid on a cold day, the next hot day you might find a little bit of fluid weeping out of the vent cap on top of the reservoir. Other than that, they work great.
 
Relocate the standard reservoir to right rear corner of the baggage compartment. Easy to service/check, no firewall penetration. Blue is the line routing. Splitter is custom. No plastic lines for me, thank you.

67lape.jpg
 
Relocate the standard reservoir to right rear corner of the baggage compartment. Easy to service/check, no firewall penetration. Blue is the line routing. Splitter is custom. No plastic lines for me, thank you.

67lape.jpg

Clean install, Dan. Another of your ideas I'll be utilizing.
 
I blew out my left brake the other day. Apparently the o-ring let go, because a few days later, I returned to my hanger to find a trail of hydraulic fluid on the hanger floor. I removed the caliper, and found evidence of fluid around the piston margins and on the disc and pads, but no extruded o-ring. Anyway, I removed the piston and found some mild scoring on the side of the piston that was easily sanded off, and no damage to the cylinder. There was a very small amount of dirt/debris in the residual fluid. What was interesting was the o-ring - which didn't look particularly damaged - but was almost perfectly square in profile and seemed to fill the seat in the piston (the new one is round.) My question is: will an o-ring take on a square profile once installed and in service, or is this clearly an incorrect part? I also found that the pressure plate is slightly warped (which I cannot pound out,) and a previous owner or builder did a bad job drilling out old rivets (two of three are oblong.) Could this have caused the brake failure?

Related to this thread is the reservoir. Mine is installed on the engine side of the firewall, with a fairly long run of clear tubing forming the low pressure supply side of the system. I can clearly see that the left channel is empty of fluid, but the right side also has air in it - trapped in a high area underneath the baggage floor between the master cylinders and the adel clamps under the rear bulkhead of the baggage compartment. I just ordered the Matco individual reservoirs - I don't like the idea of any air in the system.
 
Last edited:
Air between the reservoir and the top of the master cylinder shouldn't enter the system unless the fluid level isn't being replenished in the top of the system.
The reverse bleeding process should flush air out all the way to the reservoir, just make sure you have a way of catching the overflow.

Individual reservoirs work well, but make sure they don't foul the firewall, especially if you have them in a forward position.

The sudden blow out of the fluid and square shape on the O-ring make me wonder if you may have put in the wrong type of fluid recently. The standard seals are Buna-n material and only compatible with the 5606 type mineral based fluids. The wrong fluid will damage seals very rapidly.
 
Air between the reservoir and the top of the master cylinder shouldn't enter the system unless the fluid level isn't being replenished in the top of the system.
The reverse bleeding process should flush air out all the way to the reservoir, just make sure you have a way of catching the overflow.

Individual reservoirs work well, but make sure they don't foul the firewall, especially if you have them in a forward position.

The sudden blow out of the fluid and square shape on the O-ring make me wonder if you may have put in the wrong type of fluid recently. The standard seals are Buna-n material and only compatible with the 5606 type mineral based fluids. The wrong fluid will damage seals very rapidly.

Interesting theory re: the wrong fluid. I've only owned the plane for a few months, and I've never added any fluid other than gas and oil. All I can say is that it's red... Anyway, part of the reason to change to individual reservoirs
Is to make it easier to check the fluid level before each flight without having to remove the cowling. My pedals are a few notches away from the firewall, and I'm the only insured pilot😉. I'll drain and change the fluid to the proper stuff, and change the o ring to Vitron(sp?) How about the pressure plate warping! And the oblong rivet holes? Would it have caused the failure? When I position the new lining on the plate, you can see a gap between the plate and the lining.
 
Grove Aircraft Brake Master Cylinders with integrated reservoirs

I will install Grove master cylinders with integrated reservoirs.

Part # 682-37
Master Cylinder Assembly
5/8" Bore
7.5" Pin to Pin
Upper: 1/2 Eye Bolt
Lower: 90 Deg Out, Slotted (RV8 Style)

Capturedrsquoe3010cran2014-10-30a3000125344.png
 
RV-8 Brake Fluid Reservoirs

Happy New Year Everyone!
Please could someone post photos of Brake Reservoirs mounted on 90 degree elbows? We have in flight adjustable pedals and are currently suffering the issue of reservoirs contacting the firewall. We are wondering whether to attempt to mount the reservoirs inboard or outboard of the brake cylinders. Inboard (toward the centre) might come very close to the adjustment mechanism; outboard might be too close to the pedal when depressed.
Also, any tips on mounting the resrvoirs on the elnows? Is it necessary to remove the rudder pedal assembly from the aircraft or is it achievable in situ?

Many thanks,
Chris H - RV8 G-NRFK - UK
 
Relocate the standard reservoir to right rear corner of the baggage compartment. Easy to service/check, no firewall penetration. Blue is the line routing. Splitter is custom. No plastic lines for me, thank you.

67lape.jpg

I'm getting ready to run the brake lines and trying to understand the issue with the stock design. Is it leakage on the low pressure supply line between the plastic tubes and the metal fittings, or something else. I'm 6'2" and don't want to give up the last inch of rudder pedal position to install the individual reservoirs.

Dan, I don't quite understand the reason for this modification. My firewall came with a hole for the brake reservoir. Is there something else I'm missing?
 
Maybe I'm paranoid but...

I also moved my brake reservoir to the same location (forward baggage compartment) shown in Dan's post above. The potential for spreading an engine fire inside the cockpit was my main concern.

I don't know how flammable the brake fluid is but I did not like the idea of a reservoir of it hanging just forward of the firewall with a hole leading to a plastic hose inside the firewall. It would seem that an engine fire could easily melt the plastic hose dumping the fluid into the cockpit... Even if the brake fluid did not catch fire the resulting hole in the firewall would not be good...

So far no spillage with the baggage compartment location....
 
Brake Accumulator

I've found I'm procedurally-challenged when bleeding my brakes. Keeping the accumulator outside the firewall makes cleaning spilled fluid a lot easier!
 
I'm getting ready to run the brake lines and trying to understand the issue with the stock design. Is it leakage on the low pressure supply line between the plastic tubes and the metal fittings, or something else. I'm 6'2" and don't want to give up the last inch of rudder pedal position to install the individual reservoirs.
Dan, I don't quite understand the reason for this modification. My firewall came with a hole for the brake reservoir. Is there something else I'm missing?

I am also 6'2", so individual reservoirs were out, and besides, they are a royal pain to reach/service in any RV.

Regular readers know I made a serious effort at fire-hardening my -8. Having measured structural temperatures of a firewall assembly (aluminum angles ~300F, 5 minutes into an FAA-standard firewall test, with a good insulator/reflector on the forward side to protect the structure), there was no way I was using plastic fittings in a firewall hole, or running plastic tubing full of flammable fluid across hot 6061 angle.

This system is serviced while I stand alongside the airplane, and cannot create a fire problem. Not that it needs much service. Being all AN hardware and steel braided brake line, it doesn't leak or need bled. Fire aside, I don't understand why anyone straps into an 1800 lb vehicle with 40 gallons of gas, then bets stopping power on plastic lines with compression fittings.

If you have a need to "top up" the reservoir, you have a leak, so stop topping and start fixing.
 
Last edited:
Messy?

Someone, some where, talked about a better way to do the brake reservoir system for the RV-8. Apparently the stock system can be quite messy and a pain in the butt. Some company sells a better reservoir for this application. Anyone have any ideas ? Cant remember where I saw this .

I just noticed this thread, and I have to disagree with the statements above. I have been using the stock brake reservoir set up and it is neither messy, nor a pain in the butt. In 380 hours, it has not leaked one drop of fluid. It's plenty easy to check the fluid level during an oil change when the cowling is off.

Skylor
 
Bleeding Brakes

I've found I'm procedurally-challenged when bleeding my brakes. Keeping the accumulator outside the firewall makes cleaning spilled fluid a lot easier!

With the reservoir in the baggage compartment, I simply screw a "hose barb" into the top and run clear plastic tubing to a collection bottle on the floor. When I remove the tubing I wrap a small piece of rag around the barb to catch a couple of drops from the hose, then use a small syringe to empty the hose barb before removing.

The only "spillage" I've had has been from the "pipe" threads. These would appear to be leak free after bleeding, but they would start slowly dripping several weeks later. This was resolved by re-doing them with "LockTite" sealant, the number of which I cannot remember but is mentioned in other threads...

You do need to be careful topping up the reservoir, but have not had any problems using a pump style oil can...
 
Master cylinder mounted reservoirs

Helped a friend bleed his -8 with mounted reservoirs a couple of weeks ago. Really made me appreciate my version of the Dan Horton mounting. However, I havent added juice yet so I have to stop short of a full endorsment.
 
Had I seen DanH's installation before I installed my brake reservoir, I may have copied it. But the per plans installation has worked flawlessly for me for 265 hours. Please recall that the much maligned plastic tubing carries no pressure and all the plastic fittings are aft of the firewall. If they melt and fluid ignites from a fwf fire, I will already have unbearable heat in the cockpit.
 
Replace nylon lines

I don't mean to hijack the thread but I think my question is relavent to the discussion.

Can't seem to get the lines to play nice with each other. With the adjustable pedals and the diferential articulation it seems like there is no way to keep them from rubbing each other. Tried using Adels in a sister arrangement but they still rub each other. And I havent got the baggage floor in yet but it appears that when the pedals are adjusted aft (for the short of statue) they will balloon up and rub on the underside of the floor.



Stainless braid against nylon seems like a bad idea.
 
More adel clamps, the zip tie separator trick, or individual cylinders. Does your stainless have anti chafe coating over it?
 
Last edited:
More adel clamps, the zip tie separator trick, or individual cylinders. Does your stainless have anti chafe coating over it?

The lines move in different arcs, so more Adels will just put the lines in a bind somewhere in its range of motion. Wont go with individual cylinders-see previous pages of this thread. And no anti-chafe.
 
Someone has experienced this before

This is a bump to see if anyone missed it the first time around. Brake lines rubbing can't be just my problem.
 
This is a bump to see if anyone missed it the first time around. Brake lines rubbing can't be just my problem.

Are you talking about the two stainless braided lines rubbing each other? It appears you twisted them when you tightened the nuts, as in Fig 2 below:



It's easy to do in this case, as these particular lines have no stationary nut to allow holding counter-torque with a second wrench while tightening the flare nut. Without it, the hose very often gets twisted a few degrees, and takes the characteristic S-curve appearance we see here. They will lay parallel if not twisted. Sometimes you need to use a pair of pliers or similar to slightly twist the hose the opposite way until the nut is snug, then release and torque the nut, resulting in a no-twist final install.

As for hitting the underside of the baggage compartment with the pedals full aft, it sounds like you need shorter lines. I don't know for sure, as mine are ground adjustable and have never been moved.
 
Last edited:
Thanks Dan.
I did work on the twist but it seems even if they were perfectly parallel in neutral they will squirm at full articulation.
Maybe I'm overthinking this one.
Braided stainless against nylon seems like a bad plan. The hoses are factory so I would hope the lengths are correct.
 
I had this same issue and played around with the "twist" until it went away. The other variable is the angle of the fittings from the master cylinders...

If you can't resolve it to your satisfaction, you could try installing some plastic "split loom" on the braided line to avoid chafing, or even wrap em with some of that silicone tape that sticks to itself...
 
Last edited:
I had this same issue and played around with the "twist" until it went away. The other variable is the angle of the fittings from the master cylinders...

If you can't resolve it to your satisfaction, you could try installing some plastic "split loom" on the braided line to avoid chafing, or even wrap em with some of that silicone tape that sticks to itself...

I never thought about protecting with loom. Good tip. Thank you.
 
Back
Top