: Parking Brake Auto Release



DopeStar 156
05-10-06, 08:34 PM
I may have made a thread about this already so forgive me if I'm repeating myself.......

The unit that releases the parking brake automatically has a vacuum leak and no longer works. I can't wedge my head under there to get a decent look at it and my shop manual is MIA right now in the lost abyss of my bedroom.....

Can anyone possibly tell me how this thing works and possibly how it's leaking? Is it a hose or a diaphram or what? How easy/hard is it to remove and replace? All I see is a cylinder shaped thing with the pedal coming out of it. Anyone got a picture or a diagram? I'd appreciate it, thanks. I'm pretty sure this thing leaking is screwing with my engine's vacuum.....

CoupeDevilleRob
05-10-06, 10:55 PM
This from the 1983 manual, but the parking brake should be the same for both cars.

Parking Brake Vacuum Diaphragm

Removal

1. Remove parking brake assembly as described.

2. Disconnect vacuum hose and remove one screw that retains diapraghm and bracket to parking brake assembly.

3. Detach link that connects cylinder to manual release lever and remove diaphragm.

Installation

1. Secure link to manual release lever.

2. Position diaphragm and bracket on parking brake assembly and secure with screw and connect vacuum hose.

3. Install parking brake assembly as described.

4. Test lock and automatic release operations with engine running in Neutral and Drive ranges. Parking brake should release in any drive range with engine running and should remain engaged in Neutral and Park with engine running and "brake" light should light with park brake applied and ignition in run position.

And the diagram

http://i60.photobucket.com/albums/h17/coupedevillerob/05-10-2006104246PM.jpg

Hope this points you in the right direction.

DopeStar 156
05-11-06, 02:31 AM
I'll bet you any ammount of money the leak is coming from that stupid noodle of a vac hose... Thanks Rob.

brougham
05-11-06, 07:15 PM
I bought a new pull off thing for mine because it doesn't work. But I never changed it yet. I think the only way it can bea problem with the hose is if someone was messing around with it before and it either broke or got disconnected. But do a search for the other times you asked this question because I remember someone talked about how it works and I think they said where the problems usually is.

CoupeDevilleRob
05-11-06, 08:53 PM
"Stupid noodle of a vac hose", that made me laugh. Who would have ever though a parking brake problem could make the car run poorly? It amazes me how these things work sometimes.

77CDV
05-11-06, 11:09 PM
I'll bet you any ammount of money the leak is coming from that stupid noodle of a vac hose... Thanks Rob.

There's a quick way to test. Disconnect the vacuum hose and connect it to a vacuum gauge. Is it reading the correct engine vacuum? If yes, suspect the diaphragm in the parking brake release mechanism. If no, it may be the vacuum line to the parking brake (or another vacuum hose). Good luck, Dope.

Craig

Junkman
05-12-06, 11:52 PM
Rubber vacuum hoses deteriorate after 20 or so years, so don't be surprised to find that it is a hose. If you can see the release vacuum chamber, then gently squeeze the hose with a pair of pliers that you have put some electrical tape over each of the jaws first. You tape the jaws so the grooves on the pliers doesn't tear the hose. If the engine smooths out when you clamp the pliers on the hose, then the leak is beyond where you have squeezed. It can be the vacuum canister or it can be the hose where it enters the vacuum canister. To check this, take the hose off the canister and plug it with a golf tee. If the engine idle smooths out, then it is the vacuum chamber. If not, then there is a leak in the hose. Usually you can see the age cracks in the hoses when you look at them with a flashlight. Just try not to disturb too much under the dash, because you might be opening up a bigger can of worms than you already have....... Junk..

N0DIH
05-13-06, 02:10 PM
Mine doesn't work, the vacuum diaphram is ok, but between the diaphram and the engine is a leak that I can't seem to find.

I can't find the vacuum switch under the dash. Mine is a 94. I haven't found it in the FSM yet...

DopeStar 156
05-13-06, 03:02 PM
I went under there and I could only reach up so far but I felt the vac line and I can't tell at all. What's the best way to get access to this pain in the ass?

CoupeDevilleRob
05-13-06, 03:12 PM
The underdash/firewall area on these cars is horrible. I had to change a fuse once and went out of my mind. Patients and determination is the only way you can work under there.

77CDV
05-13-06, 05:44 PM
Ok, this is going to sound condescending, but you did ask.:) First, d/c the fuse controlling the underdash courtesy lights, or they will blind you while trying to see wtf is going on. Also, they get damn hot. Next, run the driver's seat as far back as possible, and tilt it back as far as it can go. Make sure the door is wide open, and that's as good as it's ever going to get. Just remember that it's a rat's nest of electrical and vacuum wires under there. Getting underneath has never been my problem, but then I'm kinda small. Good luck.

Craig

DopeStar 156
05-14-06, 03:45 AM
Exactly how long is that vac line? Where's the other end of that thing?

Addition: I took it upon myself to contort myself to fit under there and successfully did so. The vac line which is a skin colored line I traced to a dead end on the steering column all the way by the firewall. It just seems to end there. How does this thing build vacuum?

Also poking around under the hood I found a huge ass mouse nest right by the ILC on the passenger side. I took a shopvac and sucked that shit out. I wonder if that'll make a difference....

77CDV
05-14-06, 01:41 PM
Exactly how long is that vac line? Where's the other end of that thing?

Addition: I took it upon myself to contort myself to fit under there and successfully did so. The vac line which is a skin colored line I traced to a dead end on the steering column all the way by the firewall. It just seems to end there. How does this thing build vacuum?

Also poking around under the hood I found a huge ass mouse nest right by the ILC on the passenger side. I took a shopvac and sucked that shit out. I wonder if that'll make a difference....

Dope,

I hate those meeces! Please tell me you have a nice bat that needs feeding.:)

I tried checking the FSM to figure out your question of where the line ends. It was unillumination, to say the least. I suspect it must tie into the intake manifold somehow, as that would explain it's operating only when the car is running and only when shifted into a motive gear. I would go and trace the thing (because now I really want to know), but recent minor surgery prevents me from doing so.:mad: Did the line appear to go through the firewall, perhaps via the steering column? Enquiring minds want to know!

Craig

Junkman
05-14-06, 01:55 PM
Generally speaking, the line goes from the neutral safety switch to the vacuum release canister. That is how it was done in the past, but I don't know if this has changed. I do have a 1977 Shop Manual, and I will check when I have time.... Junk...

DopeStar 156
05-14-06, 02:50 PM
It just plugs into a piece of sheet metal..... That's the best way I can describe it.... It goes, plugs into a flat piece of metal, and behind that piece of metal, nothing..... It's so confusing....

I did manage to play with the release system with the car off in park, and I can't really tell if the diaphram is shot or not. I'm exactly 6 foot tall but I'm really skinny so I managed to lie horizontal and parallel with front seats and roll off onto the floor. I was able to squeeze my body under the dash with my feet firmly pressed up against the passenger side door right by the little trash bin and contort my neck enough to wedge my head between the brake pedal and the parking brake enough that my eyes were facing straight up at it. I also had a really good flash light laying next to my face pointed right up at the diaphram and I was able to follow the line with both my eyes and fingers to the dead end I mentioned before. The line seems solid and not like it's leaking. The leak is coming from the diaphram section since that's where I hear it from. The diaphram itself is easy enough to get out after studying it so I'm thinking about just replacing that and seeing if anything happenes. The leak is so bad it just no longer works at all. It took me a whopping 10 minutes to sort of slither my way out the driver's side door since my arms and legs were completely immobile. If anyone's curious, clostrophobia is not something that plagues me.....

DopeStar 156
05-22-06, 12:16 PM
The car's at the upholstry shop right now getting the headliner replaced. I just ordered a new diaphram from a dealer and tomorrow I'll throw it in. Anyone ever done this before? Is it rediculously hard?

2kflhr
07-07-06, 08:55 AM
How about an update.

Did the diaphragm fix the problem?

Mine wouldn't work on occassion and the wife said a spring broke and fell in the floorboard.

Man I need to get a Service Manual.....

brougham
07-07-06, 04:57 PM
How about an update.

Did the diaphragm fix the problem?

Mine wouldn't work on occassion and the wife said a spring broke and fell in the floorboard.

Man I need to get a Service Manual.....

Yeah it did fix his problem. He made another post about it. But if a spring fell out of it there's probably something else wrong with it.

Rob Benham
07-09-06, 01:55 AM
I pulled the pipe off the acctuator and put on a length of wiper hose. [ clear plastic will do.] Sucking on the line should release the brake. Spray the release with oil and do it several times.

Mine seems to work sometimes, but then needs the pedal pressing like the old release system. I don't know why this is, but it always seems to work and is a lot easier...and safer! than pulling the release by hand.

Assosiated rough running, might test out how far up the pipe it is, by a change when you select drive. However, the load on the engine will of course make a change anyway, so you need to be able to tell the difference.