Hi. I’m new to this forum, so if this is the wrong place to post this let me know. I’m in the process of buying my first truck, a 1966 25,000 GVW, possible a C60? The brakes don’t work on it. I started looking, and found that the master cylinder is locked up. I went to Napa and asked if they could get a new cylinder and/or rebuild kit, they look everywhere, even other parts websites. They had a master cylinder that was really close but it had a neck, instead of being flat where it bolts to the firewall. So where do I get a master cylinder? Thanks.
I would take it apart, hone it out, and see if one of the Napa rebuild kits will have the internal parts you need. The one with the neck, I am assuming it is Napa part # 34403, shows a 1 1/8" bore. Does yours have the same bore? Will the neck hurt anything, or will it still fit in the truck? The reason I am asking, it looks like Rock Auto shows the same one, yours may have been replaced t some point and not be the correct one.
Does this have a hydro-vac unit on it as well? look at the cardone 1057577 or 1057579 on Rock Auto. those look like your master cylinder, just need to get the correct bore size.. (I looked under 1969 C60 with 327 engine)
The truck has vacuum assist brakes, a straight 6 engine (292?), tandem axle. The Cardone 1057577 looks right, except where it bolts to the firewall, it’s clocked wrong. And the master cylinder I have now is 1 1/4” bore.
The 1034403, doesn’t have a bleeder valve. Maybe it doesn’t matter? I just want to get the right one. As you may be able to guess, I’ve never worked on a truck before. Thanks for all the help so far.
Over the years master cylinders were often changed out to what was available. For a long time the big bore cylinders were not available and guys used the pickup ones. I would try to find out what size bore originally came with your truck and find that size for optimum braking.
The 1034403, doesn’t have a bleeder valve. Maybe it doesn’t matter? I just want to get the right one. As you may be able to guess, I’ve never worked on a truck before. Thanks for all the help so far.
You don't need a bleeder valve on a master cylinder. All you have to do is (slowly and carefully) loosen the line connection(s) until fluid comes out. Then retighten it.
Good luck in searching for a new master cylinder for your truck. I have a 1966 GMC 5500. Yours might be heavier duty. I replaced a two chamber master cylinder (clutch and brake). The brake line led to a hydrovac unit that has also needed replacing. To get a replacement master cylinder, I needed to search to find a unit with brake and clutch bores and stroke that held the right amount of hydraulic fluid. This was done with much needed help from members of this forum. The replacement part also needs to have holes in the right places to bolt to the firewall, and you need to think about the availability of dust boots. You can find my thread for this under "Master Cylinder Frustration" by JRMunn.
I'm very concerned about the 1-1/4" bore being correct...that's the size used in the small trucks and I think with Tandem Axles you need a much larger bore to fill all of those wheel cylinders. It's hard to say what's been changed over the years, so what you have in hand may not be right either.
BTW, is your Tandem Axle factory installed or is it a after market "tag axle"?
The Truck Master Cylinder parts page is very confusing, so I took a photo so you could look it over and see if it helps! You need to confirm the Series...are you sure it's a C-60 and not a C-50 or C-80?
I had a friend send me a picture of a page out of the parts book for my '69 T50 brakes. All well and good except that my truck has a heavy spring option which brings with it heavy brakes, something that was not at all obvious when I was looking for parts. I wound up getting the wrong stuff. Caution is the watch word I guess.
Mac :{)
1962 K10 short step side, much modified for rally 1969 T50 fire truck, almost nos, needs a few things
Look on the glove box door for your serial number and give us that info, then we can figure out what you have.
OK, I've done some more research and it looks like you have a M60, not a C60. The M Series are the Tandems and the C Series are the single rear axle trucks. The M60 only came as a "trailing axle" tandem with the 292-I6 as it's standard engine and it had a GVW ranging from 24,000 to 30,000 pounds, so your 25,000 fits.
So, it looks like the Parts book calls for MC p/n 3896694 (shown on page 526). AND if I'm reading the parts book right the "KIt" for that MC calls it a 1-3/4 bore...p/n 3889707 (Wagner 46434).
M = Conventional Cab Tandem 633 = 6303 series (60 Series w/ 157" wb) 6 = Year (1966) P = Pontiac Plant 107323 = 7,323 truck built at Pontiac (starting at 100001)
Service and Operator Manuals should be the same year as the truck. Parts Books should be a few years newer to make sure any late year changes are included it the manual.
Place an ad in the "wanted section" here on the Bolt and keep an eye on the big auction sites and you'll find what you need.
