c50 brake master cylinder

[marvgarr68]

I'm looking for a part number for the master cylinder on a 68 c50 with vacuum booster on firewall.
Posted via Mobile Device

[Robert1970C20rstbukt]

Dorman M630823, shows to fit firewall vacuum boosters from 1967-1969.

[marvgarr68]

Thanks

[VictoriaHardware]

From the Chevrolet Truck Parts Catalog, 1946-72, 40-60 Series, Group 4.650- Cylinder Assy, Hydraulic Brake Main

[marvgarr68]

Why can I not find a rebuild kit for this master cylinder? I have searched and searched and nothing. Anyone know of one?

[jumpsoffrock]

No,

I didn't try finding a rebuilt kt at first, I wanted the whole cylinder. After finding nothing online cheap, I went to a local NAPA that has a guy that will look at books for 30 minutes before sending you home--he is the quintessential dedicated employee.(And he likes and remembers me for my '56 Ford F100 he helped me fix 6 years ago!)

After searching 3-4 old books, he come up with nothing. I asked for a rebuild kit at that point. Spent 10 more minutes looking for that, and sent me home empty handed.

I ended up buying an old off-the-shelf remanufactured one off of ebay for I think $25. It was a gamble, but the parts were all clean and unrusted...so far it works good, but I have gremlins in my brakes still. (They appear to stick or drag over long hauls, the pedal slowly gets harder and harder, l can feel the brakes dragging in the back)


The reason I never replied to this thread is because I never resolved any of my brake problems. I didn't see the point in adding my info if it didn't even work for me. But here it is.

[Robert1970C20rstbukt]

You might try to call up a brake shop that sells stuff for big trucks. I worked part time at an old school auto parts store a few years ago and they gave me several old catalogs for older light/heavy trucks and industrial engines that were duplicates of what they already had. I found a number for the kit, GM # 3912376 and Wagner # FC-59012. Those came out of a 1970 Chevy parts catalog, the GM number crossed to a Raybestos MK478. Not too sure how accurate that is though.

[marvgarr68]

Thanks for the numbers I will save them. I bought two haldex master cylinders still in the boxes.

[jumpsoffrock]

Originally Posted by marvgarr68

Thanks for the numbers I will save them. I bought two haldex master cylinders still in the boxes.

Do you have part numbers for future reference? Where'd you get them?

Thanks, and glad you were able to find a solution.


Thank you as well, Robert

[marvgarr68]

RV349601X is the part number I got. C3492SX is the exact master that is factory C3496SX is identical. C3496SX crosses over to the RV349601X. C3492SX crosses to RV349201X. I got my from ebay I bought both from the guy just incase. No one had any of the numbers in stock all had to be ordered from manufacture. A-1 Cardone rebuilds them and has a list on there website. Precision Rebuilders also rebuilds them.

[lilymonster]

My 1968 C40 has this same master cylinder (C-3492-SX) and I just ordered the Dorman one to replace it. I also want to replace the vacuum booster at the same time. Does anyone know of where I could get a booster or what the part number is? I don't see a part number on it.

[Robert1970C20rstbukt]

The A-1 Cardone catalog shows two:

54-79400, vacuum booster with 6 3/4" pedal rod
54-79410, vacuum booster with 8" pedal rod

[jumpsoffrock]

Thanks you very much for that, Robert. That may be the next thing I do to my truck.

[Robert1970C20rstbukt]

You're welcome, I had to use the Cardone website to find those. I have a Bendix and Wagner book, but those numbers weren't any good and I couldn't find any current ones.

[lilymonster]

THANK YOU! I just picked this truck up from a rural fire dept and I'm sorting out a few issues from sitting. Its really a solid truck and it should shape up well. Newer motor, tires, and a lot more! I think the brake fluid is leaking down out of the master and got into the booster where it compromised the vacuum diaphragm. This has been my experience in the past on situations like this where you get loud sucking sound when you press the brakes... Teardown will confirm...

[Robert1970C20rstbukt]

Sure thing. Hopefully you need the cheaper one, I Googled both numbers and the 54-79400 sells for $300 to $400, the 54-79410 is around $150. Sounds like a neat truck, seems like a lot of old fire trucks are showing up here lately. If you haven't yet you can start your own thread about it and post some pics if you'd like. I've had my '69 GMC for a few years, it came from a rural department as well and it hadn't been used for several years. The truck itself runs and drives great and still pumps water, although the pump could use a servicing and have the seals and packing replaced. It has air brakes so that saves me some trouble there.