Master Cylinder mc replacement

[frog210]

How can i tell what kind of Master cylinder to get
mine on my 74 c10, manual brakes(disk front drum rear), it leaks from the gasket top area
I read somewhere that they have different push rods, compared to power brakes
The ones i pulled up at autozone says jb1 or jb3 jb5 systems(something like that)
I dont want to get the wrong one,
also to replace it do i just got to undo it from the engine area, undo the brake lines and put the new one in, or do i got to mess with the brakes inside?
Thanks Frog210

[Keith Seymore]

Here's the brake system chart showing the apply system for a '74 C10:



You can see the JB1, JB3, JB5 systems across the top, based on GVW of the truck.

The fact that yours is manual immediately makes it a JB1 system.

K

[motornut]

"it leaks from the gasket top area"
some people add fluid to a low level,then get new pads/shoes on,
and the level goes up,overflowing it
leaking from the lid? replaceable seal on it
your gona need to bleed all four wheels if you crack it

[frog210]

It leaks around the gasket area,
i took it to my brake class at school and the teacher told me it would be ideal to replace it, i guess where the seal contacts it has some rust and grooves(plus autozone, oreilys, napa, advance didnt have the gasket)
if im reading this picture right i got a JB1 system correct

Are these the correct ones i can use
http://www.autozone.com/autozone/par..._0_2867%2C3311
http://www.autozone.com/autozone/par..._0_2867%2C3311
TIA!!!

[tucsonjwt]

I just replaced the mc on my 83 C20. A local brake shop used a Raybestos MC as a replacement a couple years ago and after my truck sat for 2 months waiting for a dump hoist rebuild, I very little braking power. So, I discovered a leak around the top cover and replaced the gasket under it with one from NAPA (about $6). After a lot of fiddling with it I got the leak to stop, but there was a lot of rust on the cover and around the top edge of the mc (and this is in AZ.)

So, I bought a new AC Delco MC online (lots of places to get Delco for cheap online.) I had my mechanic replace the master cylinder and he said there was a lot of air in the lines. Braking is AOK now.

Bottom line, the gasket under the cover can be replaced, but you should probably check to make sure there is no rust in the cylinder and drain/refill the fluid.

Don't buy a Raybestos MC.

[frog210]

I typed my info into autozone and those are the two that look like the they might work, are master cylinder pretty easy to install?
Posted via Mobile Device

[77c10]

Yeah, they are a breeze to install. Might take 30 minutes if even that. I recommend bench bleeding it before putting it on the truck.

[frog210]

just so i think of it
just remove the brake lines, remove the 2 bolts from the firewall, take the old mc off, then replace and repeat the steps backwards
Correct

[77c10]

I would bench bleed the new one and get it ready to go before you do anything. Once that is done, remove the two nuts holding it on and then unhook the brake lines. Bolt the new one to the booster and hook your brake lines back up. You will need to bleed it at all 4 wheels after that. Make sure you have plenty of fresh brake fluid on hand. I just re-read your last post and realized that you may not have a brake booster so ignore my comment about bolting it to the booster.

[77c10]

I may be wrong but if you have manual brakes you may have to climb under thedash and unhook the rod from the brake pedal that pushed the master cylinder. IIRC when I converted from manual to power my old MC had the rod built into it.

[wraprail]

I'm sorry but I have to ask, you are currently in a brake class and you don't know how to do something so basic as replace a master cylinder? What school are you attending?

[frog210]

now i just got into brakes class, right now where doing all that fun stuff brakes, rotors, pads, cutting, etc...
i just had questions about the master cylinder, cus its something so important and often over looked
I just wanted to make sure i was gonna do it right by asking a few question here...

[grs]

I believe jb1, jb3, or jb5 has something to do with the power booster. Some boosters are single diaphragm, and some are two. And don't get a Cardon master cyl. I am on my third one. I have an 87. Mine has a plastic reservoir. I don't know if 87 had an all metal master or not.

[Keith Seymore]

Originally Posted by grs

I believe jb1, jb3, or jb5 has something to do with the power booster. Some boosters are single diaphragm, and some are two. And don't get a Cardon master cyl. I am on my third one. I have an 87. Mine has a plastic reservoir. I don't know if 87 had an all metal master or not.

The chart I posted above is what was used to release the brake parts to the factory. It shows the differences between JB1, JB3, JB5, etc.

For '87 the master cylinder was aluminum with a plastic reservoir (for vacuum boost trucks). Hydro boost was cast iron.


K

[motornut]

my 87 looked like that

[grs]

Originally Posted by Keith Seymore

The chart I posted above is what was used to release the brake parts to the factory. It shows the differences between JB1, JB3, JB5, etc.

For '87 the master cylinder was aluminum with a plastic reservoir (for vacuum boost trucks). Hydro boost was cast iron.


K

Keith what is the best Master cyl to buy? I tried 3 Cardon, and they are no good. And would a cast iron one from a different year work, and if so what year?

[Keith Seymore]

Originally Posted by grs

Keith what is the best Master cyl to buy? I tried 3 Cardon, and they are no good. And would a cast iron one from a different year work, and if so what year?

I'd go with AC Delco. I think you can get them through Rock Auto in addition to your local supply house.

You can revert back to a cast iron unit from a previous model year but it might take some trickery. I've had some cast iron m/c where the front chamber goes to the rear brakes and the rear chamber to the front system and aluminum units where it's the opposite (front==>front; rear==>rear) ...or vice versa...

In that case you would have to swap the brake lines. Not as straightforward as keeping your current style.

K

[tucsonjwt]

Search MC on Amazon, then try:

oewarehouse.com
oehq.com
autopartstomorrow.com
rockauto.com
gmpartsdirect.com

Rock Auto can be used to get the correct GM or AC Delco part number, then use that part number to search the sources cited above.

[stock75]

Had a bit of a fiasco getting the correct master cylinder for my truck locally a few weeks ago, went to O'Reiley, did the typical rundown and went home with what should have been a new master cylinder for my 75 with manual brakes, got home only to discover i had actually been given a mc for the 75 with power brakes, took it back and explained to the clerk what was wrong, turns out they didnt even have the option of power or manual brakes in their system so be careful they were very insistent that they had given me the right part! They ended up having to pull info up on a 70' pickup i believe, I for one will never go back to an O'Reiley after this experience.

[grs]

Originally Posted by stock75

Had a bit of a fiasco getting the correct master cylinder for my truck locally a few weeks ago, went to O'Reiley, did the typical rundown and went home with what should have been a new master cylinder for my 75 with manual brakes, got home only to discover i had actually been given a mc for the 75 with power brakes, took it back and explained to the clerk what was wrong, turns out they didnt even have the option of power or manual brakes in their system so be careful they were very insistent that they had given me the right part! They ended up having to pull info up on a 70' pickup i believe, I for one will never go back to an O'Reiley after this experience.

How did you find out it was for power brakes? Do they look different?

[stock75]

yes they are different, on the manual brakes the master cylinder has a sort of socket female type piece that the brake rod sinks into about 4 inches, on the power brake master cylinder there was only a small divet where the rod should have gone in a couple inches, not positive but if i remember right the front and rear lined from the proportioning valve may have been reversed as well.