The International Cessna^® 170 Association

Does anyone know of an STC or field approval to remove the original style brake master cylinders with the reservoir built-in, and replace them with the non reservoir type and incorporate a separate brake fluid reservoir perhaps on the firewall with hoses gravity feeding the fluid to the master cylinders. This is the design on many many planes and would make replenishment and checking of fluid level, and brake bleeding so much easier. For instance, not having to remove the pilots seat and lay on your belly to do anything. thanks
George Andre, N1471D, 1951 170A

George, that's a fairly large modification to make simply in order to change a serviceing requirement that's only performed rarely/annually.
And it's easy to check original master cyl fluid levels.... one method being to use a short piece of clear pvc tubing on a threaded fitting screwed into the master cylinder plug... the other to simply fill the master cylinder and quit worrying about it.

I'd bet you'd spend an easy thousand dollars installing your mod, and then when you're finished, you'd still have to get the mod approved.

I always just fill the master cylinders from the bottom up using a Plews oiler and a piece of attached clear plastic tubing to eliminate any air bubbles. I wind up squirting a few drops into the belly, but that seems to be keeping corrosion of the belly at bay.
Piper uses a firewall mounted can as a reservoir and if you have ever tried to bleed the air out of a so equipped Piper, you know what a really lousy system it is.
Fixed gear Cessnas have an almost fool proof system. From the wheel, it is up hill all the way to the master cylinder and it's no big deal to keep the air out and fill it full.

The short answer is George, no we don't know of an STC. Having had a Piper with a system you describe, I'll keep the 170 system. There have been a few folks that have installed a different parking brake system which utilizes a master cylinder to energize the rest of the standard system. They've had this approve on an individual bases.

Tha best answer to a parking brake system is to install the "Cane Handle" type out of a later model Cessna. It uses the existing master cylinders and all Cessna parts.

blueldr wrote:Tha best answer to a parking brake system is to install the "Cane Handle" type out of a later model Cessna. It uses the existing master cylinders and all Cessna parts.

The only reason such a system is OK, in my opinion, is because if it is installed correctly the locking-tabs on the master-cylinder actuating rods are removed. Those locking-tabs are the problem. Whatever you do... REMOVE THEM.

For filling the brake master cylinder, I used (this morning, in fact) a "Justrite" Squeeze bottle. There's a link to it below (from a random supplier). It is phenominal, and costs less than $20. You still have to remove the seat and roll on your belly, but it's very easy to control the amount of fluid. You can even use it to remove fluid (if you feel inclined to do so). Great tool.
Kevin


http://www.airgas.com/browse/productDet ... t=JTR14009

Thanks for all your answers and advice. So I will just keep what I have.
Now my next question is = both of my cylinders are leaking a bit from where the shaft leaves the unit. And they leak enough so that some fluid is noted pooling on the floor. Is there a rebuild kit with new seals or is it more advisable to just get some new master cylinders. I am smart enough to do the rebuild myself if that is a concern....THANKS AGAIN FOR THE HELP
George Andre....N1471D.....a beautiful original C170A...I would post a picture if I could figure out how....

George, just get the o-rings and lock o seal and rebuild the master cylinders. Did you realize that there should be an open vent hole in the plug in the top? What I'm saying is it is curious that fluid would be forced our around the shaft enough to pull on the belly but not get pushed out the open vent hole. When you rebuild them make sure to follow the adjustment of the lock o seal found in the 100 series Service Maintenance Manual '62 and prior other wise the master cylinder won't perform correctly.

BTW looking at the service manual, there is no seal around that shaft. Could it be you don't have a breather hole in the plug or the breather hole is plugged forcing fluid up and out of at the shaft? Of course this would probably mean the lock o seal isn't sealing correctly either.

Another tip. It is not necessary to remove the entire master cylinder from the plane in order to replace the seals. Leave the bottom in the plane attached and just disassemble the peddle from the top and remove the top with the shaft and piston. In fact it is not even necessary to drain the fluid though I like to take the opportunity to wipe the crap if any out of the bottom of the master cylinder. This is also an excellent time to remove the parking break tabs on later smooth shaft master cylinders installed in 170s to prevent their accidental activation against the fire wall.

In my absolutely non humble opinion, trying to add hydraulic fluid to the master cylinders from the top is a god awful task that should only be forced on your mother in law on an incredibly hot summer day out in the full sun.
The little plastic, vented, 1/8th inch pipe plugs are a pain in the ass to remove and reinstall. You've already had to pull out the seat and twist yourself into knots to get down there and get at it. Then if there happens to be some air in the lines from applying the brakes when the reservoir was too low, you're going to bust your ass trying to bleed it out without another helper down on the caliper working the bleed valve.
Using a Plews oiler, or other type pumping device, with a piece if 1/4 inch clear plastic tubing to watch for air bubbles, you can fill the system from the bottom up forceing any air up and out through the vented plugs. If you're concerned with spilling hydraulic into the belly. simply wrap a "catch rag" around the top of the master cylinder being worked on.

Or, get a plastic 1/8"NPT x 1/8" vacuum hose barb fitting at the auto supply and put a 1/8" clear vinyl hose on the barb side long enough to bend over and put in a jar. Screw the fitting into the master cylinder using the hose to help screw it in and keep from dropping the fitting. Then put the other end in a jar and pump fluid up from the brake bleeder on the caliper with a pump oil can specifically used for brake fluid and 1/8" vinyl tube thru the master cylinder until it flows clean with no bubbles or you are satisfied there is no more air in the system. This is the cleanest, most positive and easy way I know of to bleed/fill the brakes.

Lots of ways to "skin the cat" ..as Dick and Richard ....(aren't those names/nicknames the same??) ... have already suggested.
Another variation: Using a 1/8" hose barb and clear pvc tubing from the hardware stores, screwed into the top of the master cylinder, with the tubing sufficiently long to drain overboard (outside the cabin) into a container to catch the excess.... Use a plain, plastic bottle with a "cone"-cap (imagine a clean French's Mustard jar**) full of hydraulic fluid.... squeeze the bottle to force fluid up thru the bleeder-fitting on the bottom of the caliper until you see hyd fluid exit the cabin,..close the bleeder-fitting, ...drain the excess from the overboard-tubing and re-install the vent-cap onto the master cyl.

(Less air is sent up the system than using the Plews oil-can, in my experiece.....but in any case, with time, this brake system eventually allows any air to naturally rise to the vent-cap and escape anyway.)

I've also had absolutely no problem "topping off" a master cylinder using a common Plews (trigger-actuated oil-can) with a short piece of pvc tubing on it's gooseneck to fill the cylinder. I suspect some guys complicate their lives unnecessarily due to inexperience on this task. Get someone to show you how to do this once,...and you'll have it down, pat.

** This 16 oz "plastic wash bottle" is available from Grainger for $6.
Fill it with 5606 Hyd fluid, and attach a length of pvc tubing to the nozzle. VOILA!

A lot of worthwhile suggestions in this thread! Most of us have "been there, done that". Contorting ones body may be one of the more difficult/uncomfortable procedures, depending upon one's age, size, etc. Probably the next most challenging is either removing or replacing the vented plugs. All it takes is a slight mistake and the plug goes into the hell hole never to be seen again Yea, they can be reclaimed, but at a rather time consuming effort. It helps to have a small supply of the plugs "just in case". Anyone know a good source for them?

This may need to be split into a separate thread, but some years ago I remember seeing an advertisement in some aviation catalogue for a flexible plastic/vinyl hose that would fit aerosol cans that would facilitate spraying lubercant into hard to reach areas, especially areas where the aerosol can won't fit. Just wondering if anyone knows a source for this product?

Mod note: see http://www.cessna170.org/forums/viewtop ... f=2&t=8641 for a thread on Aerosal tube extensions.

Nylon 1/8" plug and drill vent hole. McMaster-Carr, a great supplier.
http://www.mcmaster.com/#nylon-pipe-fit ... gs/=cnqt2e

John

Thanks John. That supplier appears to have a lot of other items. A good supplier to keep in mind.