Auto release parking brake problem

[Russell Petry]

Hi, Everyone! My 77 NYB has new brakes: new master cylinder, rebuilt booster, new brake lines, new calipers, new wheel cylinders and new pads/shoes. The parking brake auto release was working well through all of this work, I could depress it past a few clicks and it would stay down until I shift the column into a forward gear - just like it was designed. It has quit working, I no longer hear the signature short his when I shift into park, nor can I depress the brake more than an inch or two. It certainly does not stay down even the very short distance I can depress it, nor can I hear any clicks. It just quit working all of a sudden. My immediate suspicion is that either a vacuum hose has come loose somewhere or has a leak. Does anyone have some experience with this issue? I will check all the hoses underneath the dash to the intake manifold port this weekend. Beyond that, I cannot find any manuals that describe in detail how it is designed so I can diagnose further. The drum brakes and the emergency cable were installed properly, I took pictures before and after to verify installation. I would prefer to fix it rather than just disconnect it.

Thanks in advance!

 

[cbarge]

Try backing off the park brake cable adjuster to give it enough slack so the parking brake can click and engage.
Hope this helps

 

[Davea Lux]

Sounds like you are not getting vacuum to the unit, check your connections.

Dave

 

[thethee]

I'm pretty sure your auto release is the same as in my 75 Imperial and if so I doubt your problem is a vacuum leak.

The parking brake is purely mechanical and it also has a manual release lever. That way, if vacuum is lost you'll still have a fully functioning brake. The vacuum is only to release the brake.

You mention you can't set the parking brake right now. IMO that can mean two things:

1) something is hanging up on the mechanical side. I'd suggest you jack up the rear of the car and pull both drums. Have an assistant apply the brake and check for obstructions at the wheel

2) not a lack of but too much vacuum to set the parking brake. Could be that the vacuum release is on all the time, preventing you from pushing the pedal. The vacuum control switch is at the base of the column. It could be stuck, giving the release a continuous vacuum signal. Trace the vacuum line back through the firewall and disconnect it from the manifold and see if that solves it.

 

[Russell Petry]

I'm pretty sure your auto release is the same as in my 75 Imperial and if so I doubt your problem is a vacuum leak.

The parking brake is purely mechanical and it also has a manual release lever. That way, if vacuum is lost you'll still have a fully functioning brake. The vacuum is only to release the brake.

You mention you can't set the parking brake right now. IMO that can mean two things:

1) something is hanging up on the mechanical side. I'd suggest you jack up the rear of the car and pull both drums. Have an assistant apply the brake and check for obstructions at the wheel

2) not a lack of but too much vacuum to set the parking brake. Could be that the vacuum release is on all the time, preventing you from pushing the pedal. The vacuum control switch is at the base of the column. It could be stuck, giving the release a continuous vacuum signal. Trace the vacuum line back through the firewall and disconnect it from the manifold and see if that solves it.

Thank you! #2 is exactly how it is behaving. This was all working after the brake work was completed, so it makes sense on what you said on this item. I will disconnect the vacuum and check the pedal. If that solves the issue, then I will see if I can get that switch unstuck or find another one.

 

[thethee]

By the way, access to that switch is terrible as it is mounted on the column pretty much at the firewall, with three bolts. I found it helped a lot to remove the lower dash cover, the bottom metal panel. Well that and some profanity, that helped too

 

[Russell Petry]

By the way, access to that switch is terrible as it is mounted on the column pretty much at the firewall, with three bolts. I found it helped a lot to remove the lower dash cover, the bottom metal panel. Well that and some profanity, that helped too

Yes, I was under there when I pulled and replaced the vacuum booster. A few choice words were developed that day! I may have bumped something under there when I put that back in place, but the parking brake was working after that, so IDK. The stuck switch you brought up is a good theory. I will report back on what I find tonight.

 

[1970FuryConv]

Yes, I was under there when I pulled and replaced the vacuum booster. A few choice words were developed that day! I may have bumped something under there when I put that back in place, but the parking brake was working after that, so IDK. The stuck switch you brought up is a good theory. I will report back on what I find tonight.

Agree with the lack of joy in removing a booster. Very little room to move and hard to get my left hand up there. I think I gave in and removed the left side front bucket seat.

 

[Russell Petry]

By the way, access to that switch is terrible as it is mounted on the column pretty much at the firewall, with three bolts. I found it helped a lot to remove the lower dash cover, the bottom metal panel. Well that and some profanity, that helped too

When I got home I started up the car and looked under the dash with a flashlight. The manual release lever was stuck all the way up and it would not come back down. I wiggled it really good and it popped back down. Now the parking brake sets and releases like it is designed. I will put some silicon on that mechanism up there so it won't get caught again.

Thanks for the excellent advice! I truly appreciate it and my NYB is happy again.

 

[1970FuryConv]

When I got home I started up the car and looked under the dash with a flashlight. The manual release lever was stuck all the way up and it would not come back down. I wiggled it really good and it popped back down. Now the parking brake sets and releases like it is designed. I will put some silicon on that mechanism up there so it won't get caught again.

Thanks for the excellent advice! I truly appreciate it and my NYB is happy again.

Awesome. Glad you got it fixed!

 

[thethee]

When I got home I started up the car and looked under the dash with a flashlight. The manual release lever was stuck all the way up and it would not come back down. I wiggled it really good and it popped back down. Now the parking brake sets and releases like it is designed. I will put some silicon on that mechanism up there so it won't get caught again.

Thanks for the excellent advice! I truly appreciate it and my NYB is happy again.

Excellent, that is the best case scenario here!