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Vans Brake Reservoir

wirejock

Well Known Member
I haven't touched the reservoir except to install it. A few days ago I wanted to remove that little vent fitting. I had to use a wrench to back it out. Threads are really messed up. It galled up the threads on the reservoir. I ran a 1/8" NPT tap in the reservoir to clean up the threads but no way I'm putting that little vent back in. The threads are a mess. I tried a 1/8" NPT die but it's so small, the die bottoms out on the hex head. I tried other 1/8" NPT fittings and they fit just fine in the reservoir. The little Vans vent is messed up.
Is there some other 1/8" NPT vent or something I can fabricate?
 
Is it one of these? search McMaster for breather vent.

Screenshot 2022-11-09 at 4.54.22 PM.png
 
How hard

How hard would it be to weld on two 90 degree fittings and add a clear hose for a sight glass to be able to check the level during preflight?
 
I haven't touched the reservoir except to install it. A few days ago I wanted to remove that little vent fitting. I had to use a wrench to back it out. Threads are really messed up. It galled up the threads on the reservoir. I ran a 1/8" NPT tap in the reservoir to clean up the threads but no way I'm putting that little vent back in. The threads are a mess. I tried a 1/8" NPT die but it's so small, the die bottoms out on the hex head. I tried other 1/8" NPT fittings and they fit just fine in the reservoir. The little Vans vent is messed up.
Is there some other 1/8" NPT vent or something I can fabricate?

Larry,
I might have one in my spares box. I’ll check today and see if I have it. It’s yours if I do.
 
Vent

Larry,
I might have one in my spares box. I’ll check today and see if I have it. It’s yours if I do.

No worries Scott. I ordered a couple feom Vans. I just hope the threads are clean. I may have to replace the reservoir. The threads are borderline. If the new vent doesn't work, I may switch to something like above.
 
A combination of Matco for the reservoir, TS Flightlines for the fitting and a little fabrication gets you this option. Not mine but I’m going to emulate it.
 

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No worries Scott. I ordered a couple feom Vans. I just hope the threads are clean. I may have to replace the reservoir. The threads are borderline. If the new vent doesn't work, I may switch to something like above.

Larry,
I also have two of the reservoirs, with the cap. I only need one for a spare, so if you want one just let me know. Just pay shipping.
 
Reservoir

Larry,
I also have two of the reservoirs, with the cap. I only need one for a spare, so if you want one just let me know. Just pay shipping.

Thanks Scott. I'll let you know.

The PCV valve option has me flummoxed.
I turn a lot of wrenches on cars.
PCV valves are designed to vent crankcase pressure out. That's backwards for a reservoir vent. At least the ones with 1/8" NPT threads. Did someone find one that flows the opposite.
 
I use a plastic threaded bung with a square top, stops fluid leaking out when you're upside down. Must be removed to let in air when the bakes feel soft.
 
Thanks Scott. I'll let you know.

The PCV valve option has me flummoxed.
I turn a lot of wrenches on cars.
PCV valves are designed to vent crankcase pressure out. That's backwards for a reservoir vent. At least the ones with 1/8" NPT threads. Did someone find one that flows the opposite.

Unless you plan to fly inverted, don't worry with any kind of valve. I worked for Kuka and we went rounds with valves to deal with a reservoir issue. The best solution ended up being a sintered breather like mentioned before, but we also never flew robots inverted.
 
Thanks Scott. I'll let you know.

The PCV valve option has me flummoxed.
I turn a lot of wrenches on cars.
PCV valves are designed to vent crankcase pressure out. That's backwards for a reservoir vent. At least the ones with 1/8" NPT threads. Did someone find one that flows the opposite.

Hydraulic oil expands and contracts with temperature. So, it goes both ways, which may be the point you are making.
 
PCV

Hydraulic oil expands and contracts with temperature. So, it goes both ways, which may be the point you are making.

I assumed the builders who use a PCV are trying to allow air in while keeping fluid from leaking out. PCV valves operate the other way. Air and fluids are allowed out of the crankcase.
Hence my confusion.
 
I assumed the builders who use a PCV are trying to allow air in while keeping fluid from leaking out. PCV valves operate the other way. Air and fluids are allowed out of the crankcase.
Hence my confusion.

Just had another idea, you could try a rollover valve. They are used on fuel tanks and are meant to let the tank breath but not let any fuel out if the tank were to rollover. Something like this plus a breather filter to prevent particulate from getting into the reservoir might fit the need.

https://www.jegs.com/i/JEGS/555/15361/10002/-1?_br_psugg_q=rollover+vent+valve
 
I assumed the builders who use a PCV are trying to allow air in while keeping fluid from leaking out. PCV valves operate the other way. Air and fluids are allowed out of the crankcase.
Hence my confusion.

A brake fluid reservoir needs to vent in both directions. As you apply brakes, fluid moves out of the reservoir and when you release them, it goes back in. You DO NOT want vacuum or pressure to exist here, as it will interfere with the design of the MC's. Therefore you either need something that vents in both directions or do what the auto makers did years ago, which was a rubber diaphragm with bellows, vented on the outside. This allows fluid to move without restriction, yet seals the reservoir from leakage or air introduction. However, you likely won't be able to get a diaphragm large enough to deal with leakage and therefore a safety risk.

A 1/16" hole in an 1/8" NPT plug is adequate for our application (small bore and stroke) and should prevent fluid from leaving the Res. The scintered bronze plug is still probably the best option. There are also two way check valves that seal, yet allow air to move in both directions.

Larry
 
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A combination of Matco for the reservoir, TS Flightlines for the fitting and a little fabrication gets you this option. Not mine but I’m going to emulate it.

I installed one of these on a Sonex (is what the owner had and wanted installed). I wouldn't wish this reservoir on an enemy. Crappy design overall, either have to fill through a tiny hole or disassemble from the mount to fill. Plus, it is plastic FWF...blah.
 
Caps

There was a guy named Alex Peterson that sold vent fittings with a check valve in them. Years ago, and I've lost the bookmark, but seems like it was reservoir dog or something like that.
https://vansairforce.net/community/archive/index.php/t-15859.html
For the sintered caps like Vans supplies: (pack of ten for $11)
https://www.amazon.com/gp/product/B0195UXY6M/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

That is funny. Never occurred to me to check Amazon. Doh!
Thx
 
Larry,

It's been established that the breather needs to breathe both ways, so a one way PCV valve won't work.
I don't see the sintered breather leaking from short negative g excursions.
For sustained negative g, an inverted flight check valve may be easily constructed.
Thread a short aluminum or brass nipple into the reservoir, and thread a short pipe coupling onto that. Find a ball bearing (just the ball) that will fit into the coupling but not through the nipple. Make sure the ball bearing makes a seal with the threaded end of the sintered breather when it's placed on the upside down breather. If not, a little work with a countersink or valve lapping compound should do the trick.
Put some notches in the top of the nipple so the ball can't seal on it, and drop the ball bearing in the coupling and attach the sintered breather.
This will be a lot cheaper than a commercial rollover valve and the threads will match.
 
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