One of our brake master cylinders is leaking again. It’s had the o-rings replaced three or four times, but always leaks again after a year or so. I saw posts recently that the Gerdes master cylinders (which we have) are no longer available. Is there any replacement for them? Any source for used ones? Beech part number is 169-380100-1 and Gerdes part number is A-110 43.
Thanks
Editor:
Assuming that the cylinder shaft is not corroded or pitted, there are four main reasons why a new shaft o-ring does not hold up:
1. A cheap o-ring was used, rather than a proper Mil-spec o-ring that is oil-resistant.
2. The shaft is corroded, pitted, or has flaking chrome. This is not a rebuildable part (at least, not at a reasonable cost).
3. The gland bushing that contains the shaft o-ring, and through which the shaft passes, has been worn to a slightly oval shape due to many years of slight shaft contact. The o-ring will no longer seal, once it has hardened slightly in service (especially in cold weather).
4. Maybe 80 times out of 100, the cylinder was rebuilt with a serviceable shaft, but the rebuilder failed to properly polish the shaft on a buffing wheel. If the shaft has no physical damage from corrosion, etc., is properly polished, is assembled with a new o-ring, and with proper lube (like Parker O-lube or their newer product), the cylinder will last nearly as long as a new one (with respect to external leaks).
My understanding, from Beech Technical Support, is that the 169-380100-1 has been superseded by the 169-380100-3. As you can confirm in the RAPID parts search, this is in fact the Cleveland Wheel And Brake CLB10-55 cylinder. Beech has these in stock for $208++. Since the 10-55 has exploded in price during the past five years, you may be stuck paying a high price if you have to buy new. I would try some online searches. If no luck, try calling Rick Leatherwood at Arrell Aircraft, where we get a BAC discount on Beech parts. Their link is on BAC. Wicks currently has the 10-55 for $165 (page link follows, be sure to copy the full link):
http://www.wicksaircraft.com/catalog/product_detail.php/pid=4611~subid=1285/