Brake frustration

[dgangle]

I replaced cheap ccot wheel cylinders with sor cylinders a little better but still not firm. Wondering if anyone has any other ideas before I toss this thing in the San Antonio river.

yea, disk brakes.... and never, never have to deal with this crap again.

 

[miker]

Are the new wheel cylinders the same bore as the old ones?

 

[MtnTrucker]

Anyone think the master cylinder is the culprit?

Doubtful. You said you had good brakes before you changed out the wheel cylinders and such. That tells me the previous MC was OK and your pedal height and travel adjustment close enough that you're getting good enough plunger travel to operate everything properly.

However you said you then replaced that MC with a new, like unit, correct? It's possible you have multiple issues. Your original MC was probably OK but your WC's were improperly adjusted. Then you replaced the MC with another unit that could be bad. Now you've gotten your MC's correctly adjusted.

As long as were grasping at straws here, put your original MC back on a bleed the brakes again. And you need to ditch the 10 lb residual valve, those are for use on disk brakes only. They keep slight pressure on the pads so a gap doesn't develop because disk brakes don't use return springs. Your stock drum setup does have return springs and a residual valve may cause them to drag.

 

[FJROSS]

I ran into this trouble a few years ago with CCOT cylinders. The only solution I found was to remove the top dustcover and piston from each wheel cylinder and let gravity push the fluid up and out, then I quickly pushed each piston back in, making sure not to trap any air. Lots of friends and "experts" said I was crazy and I shouldn't have to do that but it fixed the problem immediately and I had a hard pedal. I wasted weeks of time with other methods. Good luck.

After making sure that your brakes are properly adjusted, this was the only way that I got a hard pedal using the CCOT cylinders. I actually gave up and ordered my rear disc kit and while I was waiting for the kit to ship, we tried this similar method that cured the problem once and for all.

Dave

 

[salt1019]

Allright finally got em working. Again, I did replace the CCOT cylinders with SOR which helped a little. But, what I really learned is that you have to adjust the brakes very tight with the wheels on. When I was adjusting before I only had the drum on, then when I mounted the wheel it would totally lock up. I finally adjusted with the wheel mounted and tightened them until I could literally just turn the wheels not spin em but just barely turn em. Now the pedal is high and firm when I stomp on the brake it wants to send me through the windshield. Thanks for everyones input it really helped. As you help others please pass on that elementary piece of information... adjust tight with wheels on. I have worked brake drums before but have never seen any that had to be adjusted this tight. Again much thanks!

 

[miker]

And you need to ditch the 10 lb residual valve, those are for use on disk brakes only. They keep slight pressure on the pads so a gap doesn't develop because disk brakes don't use return springs. Your stock drum setup does have return springs and a residual valve may cause them to drag.

I thought this was the opposite and that drum brakes require the residual valve. And that if you use a residual valve on disk brakes, they tend to get very tight, even lock up, with no pedal pressure applied.

 

[salt1019]

They make 2lb and 10lb residual valves the 2lb are for disk only if you have your master cylinder mounted below your calipers. Drum brake master cylinders have 10lb residual built in. However, in my case where I have a master cylinder thats designed for disk in front and drum in the rear only the rear port has a bulit in residual valve. I used the following site for research.
Master Power Brakes - Reference/FAQs: Master Cylinders