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| | | Joined: Jul 2014 Posts: 48 Wrench Fetcher | | Wrench Fetcher Joined: Jul 2014 Posts: 48 | Yes, this is my first post - I've been a lurker for a while. I own a '55 6400 and fought the dreaded need to pump the brake pedal, despite new hoses, lines, MC, and wheel cylinders. Everything adjusted properly. Then it came to me!
I installed a Willwood 10 psi residual pressure valve in the brake line right as it comes out of the master cylinder. Part #260-3279. It holds the fluid in the wheel cylinders and doesn't allow it to bleed back into the master cylinder so you don't have to pump the pedal. One round of bleeding after the install and I get a firm pedal - first pump!
I have no affiliation with Wilwood. Here's the part:
http://www.wilwood.com/Search/PartNoSearch.aspx?q=260-3279
Best $30 I ever spent on the truck!!! | | | | | Joined: Feb 2004 Posts: 29,771 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,771 | The original-equipment master cylinder on your truck has a residual pressure valve built in. If you had to add another one, somebody has dropped the ball while rebuilding the master cylinder at sometime in the past.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Jul 2014 Posts: 48 Wrench Fetcher | | Wrench Fetcher Joined: Jul 2014 Posts: 48 | Yes, BUT the one in the old (rebuilt) master was bad so I bought a kit and the new kit also failed to work properly. Then I bought a new master cylinder and it failed to work properly. My thought is that anyone who attempts to rebuild/replace their master cylinder is going to run into the same issue, as there is only one manufacturer left for this component. The WIlwood residual pressure valve actually WORKS. It holds a higher pressure, indefinitely.
ANyone who has bled brakes on a 6400 knows its a bear. I bled the brakes ONCE, in no special order, and I have a high, firm pedal even after not touching the truck for a week. I'm posting this solution for those who end up with the same difficult to find and faulty parts as I did. | | | | | Joined: Apr 2005 Posts: 926 Shop Shark | | Shop Shark Joined: Apr 2005 Posts: 926 | Do they actually release while you're driving it? My '54 2 ton did that-I'd have good pedal to begin with,and it'd get better as I went until the brakes started locking up. I'd crack a bleeder a little and all's well again,for a while.I checked the pushrod adjustment,it was fine. I backed it off a little and that made no difference. I replaced the Master cylinder and the new one did the same thing. My solution was to build a bracket and install a mid 70's GM one ton truck master cylinder on it (Same diameter cylinder,but dual reservoir.) ,with an adjustable proportioning valve to reduce the pressure to the front wheels. (I didn't bother with the residual pressure valve,but it sounds like a good move. I'll probably do that too.) My brakes are so much better now,I don't even need a brake booster.
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