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76' K5 Rear Disc Conversion

chalet2506

chalet2506

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I didn't want to hijack another guys thread - so here's where I'm at.

dremu said:
Also in the Con category is that you *will* end up replacing your master cylinder, either because you realize your old one is worn out, or because you think you need something different for disc/disc (IMHO, you prolly don't.)

-- A
Click to expand...
Speaking of the costs and the domino effect of altering your original brake system -

I've got most of the stuff gathered(even the 14mm hex wrenches and clutch springs:D) to finally do the disk brake swap onto my 14bsf. My master cylinder is leaking and I was going to replace it while I'm at it. I'm a brake noob and this is the first thing I've done that's more complicated than changing pads.

So, I figure I've got 2 options.


Option 1

I've been reading the 1st generation 3/4 ton brake booster swap thread.

http://coloradok5.com/forums/showthread.php?t=228344&highlight=brake+booster

So I'm thinking to myself, why not just upgrade brake booster/ mc while I'm converting to rear disks. Is it possible to do this on a 2nd generation? Everything I've read is related to 1st generation blazers. I'd like to do all the brake work at once because bleeding them is going to be a pain in the butt.

Relevant details are that I'm using 76 El Dorado Calipers, I plan on fabbing my own e-brake assembly and running the calipers upside down to keep it from hanging on crap. I've got a complete stainless brake line kit coming from ORD as well. Also, I do most of my shopping at NAPA, so any relevant part #'s would be helpful.


Option 2
Or, should I just get the disks on and setup, replace the original m/c with another half ton one and be done with it. I'd like to keep it simple, but on the flip side I've got the extra weight of the camper, so I want a setup with a little stopping power.

:dunno:
 
If the calipers are on upside down how will you bleed them?
 
you've got remove them and hold them onto the frontside of the rotor - pita.
 
i heard it just has to be a 3/4 ton, not only 1st gen, any year til '87....i think my master cylinder did the same thing you were talking about, i need to replace that.....
 
chalet2506 said:
I've got most of the stuff gathered(even the 14mm hex wrenches and clutch springs:D) to finally do the disk brake swap onto my 14bsf. My master cylinder is leaking and I was going to replace it while I'm at it. I'm a brake noob and this is the first thing I've done that's more complicated than changing pads.
Click to expand...

Woohoo! Glad the wrench/spring tips are useful! :deal:

If I remember from looking the parts up, in many years the 1/2 ton and 3/4 ton use the same booster, so if you're staying with vacuum boost and your existing booster holds vacuum, you can keep it. As for replacing the master, I recommend the stock style. Here's why...

On my '74 K5 (10b/14FF disc/disc), I'm using a stock replacement master cylinder with the original prop/combo valve, and that thing will stop on a dime. That's with 35" tires, though with the 52"/56" springs it's a bit bouncy (okay, REALLY bouncy, especially if you whang on the brake pedal... but that's not the brakes' fault!) Others have reported similarly positive results with stock style masters -- if your existing one is old or at all suspect, replace it with a new, stock style one.

On my sixpack I had issues and started throwing money at it, so I tried the aftermarket prop valve and a different style master (P30 disc/disc) etc etc ... and in the end, it didn't do much other than drain my wallet and frustrate me, especially w.r.t. bleeding the brakes.

Point being that I *highly* recommend changing one thing at a time. If your master is leaking, I'd replace it with a stock style rather than dinking with it, 'cuz if you change that AND the calipers (or worse, AND the prop valve) when you have problems you'll have no idea what to fiddle with.

BTW, if you've not done hydraulics yet, read up on bleeding, especially if you're gonna put the calipers upside down (which I do NOT recommend -- check how you're gonna run the parking brake cables first!) At the very least look into building a one-man bleeder, but I really like the garden sprayer pressure bleeder. Cheap, simple, and positive results.

Mind you, I *still* loathe bleeding brakes; I've been putting off replacing the master on the sixpack (for the fifth time -- went back to stock, and it's a bit leaky, so I got a new, stock style master) solely because it's messy and requires patience ;)

Anyway, to sum up: Do option 2 first. If you have issues, post up, and we'll tell you to keep bleeding the system until the problems go away. If after two gallons of brake fluid you're still not happy, you can consider option #1 :haha:

-- A
 
thats the kind of answer I'm looking for. Its amazing how fast these things can snowball when you start putting some thought into them. I'm not 100% set on the upside down caliper placement. Like you said, I've got to get it semi-assembled and see how exactly I'm going to run the e-brake. I do like to drive through the brush, so I'm going to have to figure out someway to keep it from getting boogered up.
 
If you remember any of the hell that Matt and I had on his swap, I would also suggest one piece at a time.

A couple of notes I will give you:

If you make your own hardlines, get a QUALITY double flare tool. Make sure the flares are perfectly square. I slightly off flare can suck air but not leak fluid. Took a week to figure that out.

Do the work on flat ground and always do a gravity bleed at some point before power or pump bleeding.

Get twice the brake fluid you think you are gonna use. You're gonna use it.

Don't forget to pump the pedal after doing any brake work!!!!


Bleed the system in order, starting with a bench bleed of the MC. If you are bleding brakes on a truck with an old MC, do not push the pedal all the way to the floor. Put a block of wood or something underneath it. An old MC will have a buildup of crud on the shaft. If you start pumping it all the way to the floor, the crud on the shaft will act like a file on your MC seal. You can make a good MC go bad, just from bleeding it because of this.

In your particular situation, I would do your repairs in this order: Replace MC and bleed system. Pump pedal and test drive truck. Install Caddy calipers correctly( you may be able to rotate them up some. I would strongly advise against upside down) Rebleed system, pump pedal and test drive truck. NOw see if your brakes work like you want them to.

Special note....... On the Caddy calipers, you must use the Ebrake whenever the truck is stopped. That is what keeps it adjusted properly. If you hear of people who quit using the Caddys, they didn't do that step, probably. A misadjusted parking brake setup will reduce the function of the calipers. Similar to poorly adjusted shoes in a drum brake setup.

Some will disagree with that last paragraph, I don't care. Repeated use of the Ebrake has been the only difference I have noted between Caddys that worked, and those that sucked. Some have had good luck with them and not used the Ebrake much, but most, if not all, of the problem ones, didn't use it(or have it hooked up)

These are some of the mental notes I have after doing numerous brake swaps and modifications. If you need help, ASK. I would much rather donate a weekend of my time to you, then to have you take a chance of killing yourself because something slipped your mind, while during the work.

Leper
 
thanks for the advice. I didn't know that bit about using the e-brake to keep everything adjusted. I've already pulled the rear axle and disconnected the brakes, so I'll go ahead and get a new mc and bench bleed it - I've read you can get a kit to help with that. Probably will leave the calipers right side up then for now, to keep it simple.

Since I got the axle with no hardlines - I went ahead and got the long stainless lines from ORD that eliminate the need for them, thereby eliminating something else I could possibly screw up.

Hopefully my parts will all be in and I can get this thing squared away by the end of the week and get back to the tranny.
 
chalet2506 said:
thanks for the advice. I didn't know that bit about using the e-brake to keep everything adjusted. I've already pulled the rear axle and disconnected the brakes, so I'll go ahead and get a new mc and bench bleed it - I've read you can get a kit to help with that. Probably will leave the calipers right side up then for now, to keep it simple.

Since I got the axle with no hardlines - I went ahead and got the long stainless lines from ORD that eliminate the need for them, thereby eliminating something else I could possibly screw up.

Hopefully my parts will all be in and I can get this thing squared away by the end of the week and get back to the tranny.
Click to expand...
i have my caddy calipers turned upside down so they sit up front on the upper side of the axle.it keeps the calipers above the axle so it cant get ripped off.it also puts the ebrake cable in a better position for straiter operation.i like this setup better.to bleed them you just have to put it on the other side facing up and it was no problem.after bled just put em on upside down again.they work fine.i didnt have the ebrake cables hooked up for a while,and i didnt see any difference.
 
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