Jump to content

Front Disc brakes LOCKED 1979 620

Recommended Posts

Searched, couldn't find the exact answer i was looking for.


Recently purchased this truck, and everything while "original" was pretty tired. I bled the brakes on all four, and even went ahead and installed a rebuilt master cylinder (3/4") on the truck (everything was spongy after the bleed). Everything seemed fine and I even had the truck on the highway without issue. Drove it fine the day before the issue started up, but now the front calipers seem locked on the front discs.


Drove it about 8 minutes without too much issue (albeit dragging slightly), but on the drive back the fronts began to smoke and rolling is pretty much out of the question.


Any insight on this? I found a different post earlier,


but this doesn't seem to exactly answer my particular question.


thanks in advance.


Share this post

Link to post

drums on my 521 did something like that..got tighter and tigher after several stops. Problem was I didn't have any extra slack in the brake pedal, so when I took my foot off the brake pedal,  the pushrod in the  MC was just barely unable to fully come back out. not sure if same for you, but the brake pedal has to allow the MC piston to fully back out when you're not on the brakes. Otherwise there will be this continual build up of a tiny amount of pressure in the brakes. Should be just a bit of play when you're not on the brake pedal.

Share this post

Link to post

Yep, sounds like a case of the master being out of adjustment. You need about 1/16" of free play at the rod going from the pedal to the master. Any free play is ok, but 1/16" is safe.

Share this post

Link to post

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...

Important Information

By using this site, you agree to our Terms of Use.