1965 L320 brake cylinder

[Crusty320]

My family has this L320 since production and has been kept mostly stock throughout the years only replacing the carb, air filter, fuel pump, and replacing the generator for an alternator for convenience. it’s finally running but has no brakes due to a bad brake cylinder have tried local to find a replacement but no luck. Any ideas are welcome would love to get this truck road ready.

 

crusty

[mklotz70]

ebay is probably you're only option for stock parts.  

 

There are guys converting the fronts to disc brakes....you might be able to find some "take offs".

 

Worst case, you can convert to later model(520/521/620) drums. Easiest to just swap the entire backing plate with all of the parts on it.  If you have to use 620, you'll end up with metric parts to deal with.  If you need to go this route, it would be best to do both sides.  That's true for you wheel cylinder, too....best to do both.  

 

They're simple devices, so you might expand your search to include rebuild parts.

 

Edited August 20, 2023 by mklotz70

[Zippy67roadster]

The brake cylinders fro the 521 truck are identical for the front and rear.  I picked mine up on Rockauto.

[Crusty320]

On 8/19/2023 at 4:00 PM, Crusty320 said:

My family has this L320 since production and has been kept mostly stock throughout the years only replacing the carb, air filter, fuel pump, and replacing the generator for an alternator for convenience. it’s finally running but has no brakes due to a bad brake cylinder have tried local to find a replacement but no luck. Any ideas are welcome would love to get this truck road ready.

 

crusty

A quick update on this I was able to get the drum off and replace the cylinder but that didn’t stop the brake fluid form leaking I think it may be the part in the picture below I don’t know what it is called or how to replace it can anyone help me out?

thanks, 

crusty

[difrangia]

That's the adjuster. Doesn't have much to do with the fluid unless it's adjusted down so far that the pistons extend enough to leak. I'm not first-hand famailiar with adjusting the drum-brakes but it looks like it is adjusted in pretty much all the way. With the wheel-cylinder pistons pushed in all the way and the shoes on, this should be adjusted out till the drum just slides on to the shoes and then adjust the shoes out to proper clearance after bleeding the cylinder.

[Crusty320]

UPDATE

i have been messing with the brakes and replaced parts as needed but have hit a new roadblock when messing with the adjuster thing. It’s rusted to its self and won’t move I think the safest move would be to get a new one any suggestions on where to pick one up?

 

[Stoffregen Motorsports]

You can usually free them up by soaking and heating. Do you have a heated ultrasonic cleaner? That might free it up.

[Crusty320]

On 10/30/2023 at 8:37 AM, Stoffregen Motorsports said:

You can usually free them up by soaking and heating. Do you have a heated ultrasonic cleaner? That might free it up.

i've tried that it wont budge i'm thinking just for safety's sake I should look into getting a new one

[Stoffregen Motorsports]

New one? Good luck!

[wayno]

I would take the adjuster out, put it in a vise, and pull it apart, you might have to use a punch to get it apart, then clean it up, I use a bench grinder with a wire wheel, then I put it back together, I make sure everything turns smoothly, then I put it back into service.

 

As I recall they use the same adjuster all the way through 720.

[datzenmike]

2 hours ago, wayno said:

 As I recall they use the same adjuster all the way through 720.

 

From '65 at least, on the 520/521/620 and 720 till December '81.

 

If you do get it apart use lots of anti-seize.

[Crusty320]

UPDATE

I bought a new cylinder for the truck but now the drum won’t go in I think it because the cylinder is slight larger the one I got is from the 521 I was told it would work but I don’t think it’s the right size. Did I get the wrong cylinder? Or is it possible I did something else wrong?

[datzenmike]

Sometimes the shoe linings are thicker than stock or they intend that the owner have them turned down to true them up. I replaced by B-210 shoes in the '70s and this had to be the case. Grind down the contact patch on the shoes where they ride on the wheel cylinder till they fit..

[wayno]

Sometimes one has to loosen/disconnect the e-brake from the center pull under the truck, then install the drums, then adjust the brakes, then put the e-brake assembly back together and adjust it.

[Crusty320]

I ended up filing down the shoes so they would fit on the 521 cylinder I went to bleed the brakes and the proportioning value  is a mangled mess it looks like someone tried to solder it shut so I’m gonna have to get a new one I haven’t had luck finding any that would work, I hope to have this truck done before winter fully hits. any help is welcome.

[MikeRL411]

On 11/13/2023 at 11:10 AM, datzenmike said:

Sometimes the shoe linings are thicker than stock or they intend that the owner have them turned down to true them up. I replaced by B-210 shoes in the '70s and this had to be the case. Grind down the contact patch on the shoes where they ride on the wheel cylinder till they fit..

 Replacement brake shoes were historically oversized so that they could be sized to fit the actual curvature of the drum. Brake lathes were designed to do this final fitting.  in addition to machining the ID of the drums