The International Cessna 170 Association

My left brake has been leaking fluid giving a spongy pedal. Some drops noted on hangar floor but not enough to cause me concern. After topping up the brake fluid the pedal was spongy after only a few flights.
My maintenance shop took the caliper off and found numerous pits on the cylindrical surface. The piston is fine.
Any thoughts on repair or replacement? Do the calipers come cheaper in pairs, or can I just replace the bad part?
Thanks Eric
PS any part numbers or source info would be greatly appreciated.

Inspect the other side and see if it is in the same shape. It probably is and just has not started leaking yet. Check with the discount aircraft parts houses in Trade-A-Plane and call them all. I tend to replace items like brakes and tires in pairs to give equal time in service.

For future reference, remove your brake calipers, clean, and replace o-rings every year at annual. It is cheap insurance compared with an accident rebuild. Do it even if your maintence engineer says they should be ok. Of all the places to scrimp and save money on an airplane, wheels, brakes, and tires is not one of them.

The caliper cylinder is aluminum and subject to corrosion. This can occur when pressure washers are used to wash the airplane, it can happen when the airplane is taxied thru water puddles, or if the wheel gets submerged on a soft field, etc.. Once the corrosion pits occur, the rubber O-ring seal on the piston is damaged and the caliper will leak fluid. (By the way, ... NO amount of drips are permissible. There is no such thing as a little brake leak, or a little bit pregnant.)

The fix is to replace the caliper with a serviceable unit. You might get lucky and find one in salvage condition that's good, but generally it's best to simply buy a new one.

If you can read the data tag on your existing unit, order an identical unit. If you can't read it or if it is missing, use the data in your STC kit. (If you have the standard conversion kit for a C-170, the caliper PN is: 30-63A.

Hope this helps.

For a distributor near you: 1-800- 272-7537 (800-c-parker)

Hi Eric,
I am in Oshawa, I have a spare, serviceable, Cleveland single puck brake caliper assembly, if that is what you need ?
It looks lile I am going to,KFLL tomorrow , evening , until Sunday.
If you want it, I can leave it at our hangar , in YYZ ?

or come over to CYOO , and have a coffee and pick it up, next week ?

john

I had the same problem,but however I have dual piston brake calipers [cleveland] and could not source new here in Oz. So after a chat with the Feds , we raised a engineering order to press a stainless steel sleeve in the bore. The caliper was machined out to accept the sleeve. We still use the orginal pistons. The oil gallerys were line bored.Everything is working well, no leaks or spongy brakes after 3 years of operation.

Ghostflyer, that is an excellent solution!

A similar solution is used in an analogous, although different application: Wheel bearing grease-filled axle-caps on boat trailers. (Commonly called by a trade-name, "Bearing Buddies") Their spring-loaded pistons (which keep grease under pressure against the wheel bearings, to prevent water ingress when the boat trailer's axles are submerged, have an O-ring seal similar to our brake calipers. The mfr'r offers a stainless "cup" insert that re-lines the hub which the piston rides within. It's what I immediately thought of as a potential solution to this Cleveland brake problem. Of course, a basis of approval would be necessary, and the mfr'r would probably prefer to sell new calipers.... ... but the fact that I thought of that and you thought of your solution shows that GREAT MINDS THINK ALIKE.

I suppose boring the cylinder out and installing a larger piston could also be done.... but again, ...basis of approval.

George,

You're certainly right about a basis of approval for a .040" bored out brake caliper cylinder and .080" oversize piston. It would never get by either a ramp check by the FUZZ or an annual by the average AI.

blueldr wrote:George,

You're certainly right about a basis of approval for a .040" bored out brake caliper cylinder and .080" oversize piston. It would never get by either a ramp check by the FUZZ or an annual by the average AI.

Like yourself, bluEldr, I'd just call that a REPAIR!

But if the brake failed and someone got wrecked, hurt, or killed, the lawyers would have a field day.

A little simpler, same idea, for the single cylinder is a thin, hard Stainless sleeve from NAPA that is for putting on the seal area of a pitted shaft. Don't remember the size but there is one that makes a press fit into the brake housing. ( .0015-.002" over ) Need to grind out a notch for the fluid intake hole ( Too hard to drill ) then grind off the excess that sticks out. Chuck the center piston in a drill and file it untill it just moves freely in the new sleeve, add the O ring and it works good. Been that way for 15+ years with no problems. Think I put a adhesive sealant in the cylinder before pressing in the sleeve, probably over kill though.