'62 Parking Brake Mechanism Repair

[Gary Christensen CLC # 21112]

The pedal for the parking brake on my 1962 Eldorado has not been working correctly and I have removed the pedal/release mechanism to repair it.  The symptom was that the pedal would not stay depressed when I stepped on the parking brake.  I would have to push up on the manual release in order to set it.

Now that I have the unit out, I believe that there is a piece missing.  When depressing the pedal, I believe that some sort of linkage is supposed to pull on the arm that primes the vacuum diaphram, which is the same effect if I lift the manual release arm by hand.  Once the diaphram arm is "cocked", it locks the pedal in the down position.  Subsequently, when I suck on the nipple for the diaphram, the arm releases and the spring under the car (via the cable) pops the pedal back to the up position.  Pulling down on the manual release also pushes the diaphram arm in (which is how you release it if the vacuum release doesn't work).

There is nothing on my unit that pulls on the diaphram arm when I depress the pedal.  There's a second hole on the mechanism that looks worn at a particular spot, as if there were some sort of spring or something that has worn a little groove over the years.  It's just empty.

Do I correctly understand how this works, and if so can anyone describe for me what I'm missing (or alternatively what is supposed to engage the diaphram when the pedal is depressed)?

Thanks.

Gary

[quadfins]

Hi Gary,
   I'm just about to leave for the evening, but I have tomorrow off and will be doing some car projects. I'll check the parking brake system on my '61 and see what I can find.
   I also might have the cruise control gear from a '63. I'll dig through the shed in the morning, and we can measure and see if it might work for you.  Though I don't know what condition it is in...

Jim

[Gary Christensen CLC # 21112]

Thanks Jim.

I had to take the brake pedal mechanism off in order to figure out what is going on, which includes crawling under the car to disengage the cable.  Hassle!  But you might be able to see the mechanism from the side.  The service manual of course doesn't have any pictures of the actual mechanism -- just the steps to remove and install it.

Thanks for the offer to check about the gear.

Gary

[Dan LeBlanc]

I had the exact same problem on my 61 Fleetwood.  Once I got the car in a state of total disassembly, I was in the mood to tinker with something one day.  I lubricated all moving parts with a bit of engine oil, let it soak for a couple of days.  When I came back to it, everything tested fine on the bench.

The car is still disassembled, however, so it's still sitting in a box.

[Gary Christensen CLC # 21112]

Dan,

Thanks for the info.  My problem is that I don't see any physical means by which the pedal actually interacts with the diaphram on the downward stroke.  There's a bar that locks the pedal down if the manual lever is pushed forward and "releases" when the diaphram gets vacuum, but the geometry is such that it doesn't engage when the pedal is engaged.  That's why I think ther must be something missing.

Gary

[Dan LeBlanc]

If I remember correctly, there should be some small linkage that connects the vacuum part to the release part.  I'll see if I can find the box mine is in and post a pic.

[The Tassie Devil(le)]

Isn't there supposed to be a spring that locks the locking pawl into position when the pedal is pressed, and it is only released when the Vacuum Diaphragm is evacuated when shifting out of Park?

The ratcheting mechanism isn't supposed to lock into position until the gear lever is placed back into Park.

Is the Neutral Start Switch (NSS) correctly lined up, and the Vacuum switch part of it working?

Bruce.

[Dan LeBlanc]

Here you go . . . hope this helps.

[quadfins]

Hi Gary,
   I tried to send you an email with some pics and explanation, but it bounced back. Send me a PM direct, and I'll try again as a reply.

Jim

[62droptop]

i have a 1962 park brake assembly out of the car if you need any other pictures

[Gary Christensen CLC # 21112]

Thanks everyone.  I am missing the spring shown on Dan's photo.  But the photo doesn't show where the other end is connected.  Another photo please?

[Dan LeBlanc]

I'll snap one over the weekend for you.

PM me your email address and I'll send it direct from my iPhone.

[62droptop]

Dan, got you covered buddy

[62droptop]

second picture

shows location well
there is a tab up near the mounting holes

[Gary Christensen CLC # 21112]

Everyone,

Thank you a ton for all of the pictures.  I am definitely missing the spring, but after a ton of cleaning and thinking and fiddling with it, I'm pretty sure that the missing spring is not the problem.

My unit looks just like Dan's, but without the spring.

The issue I have is that there is nothing to engage the piston on the diaphram when the pedal is pushed.  Looking at all of the pictures and the geometry, and testing by sucking on and blowing on the diaphram nipple, I'm convinced that the only way it will work is that there must be pressure on the "vacuum" line when the car is not in Park.  The operation of the unit works perfectly if I blow on the nipple (i.e. apply pressure) as I engage the pedal.  When I suck on the diaphram (i.e. apply vacuum) the unit releases perfectly.

I see no place for a mechanical linkage (missing or otherwise) that would engage the diaphram when the pedal is pushed, spring or no spring.  The unit can only work if the diaphram arm is pulled out when the pedal is pushed.

Is it possible that there is something somewhere that switches between sucking and blowing on the line?  If so, where would it be?

My brake always released correctly when I pulled the lever out of park, so I know that that function works.  Does that happen in the NSS?  My NSS works, by the way Bruce.

Jim Eccleston sent me pictures of the unit from his '61, but it is different in that the "V" shaped bar that is attached to the pedal and the manual release arm is straight, not V shaped.  As I mentioned above, mine looks exactly like Dan's below.

I need an engineer!

Gary

[The Tassie Devil(le)]

G'day Gary,

The NSS has a vacuum switch that opens for vacuum in any gear but Park.

This way, when you apply the park brake, when you park, with the gear lever in Park, the brake will hold.

But, when you shift into Forward or Reverse, the vacuum switch moves, and allows engine vacuum to pull the diaphragm in, thereby releasing the park brake automatically.

It also means that when you are driving, you cannot lock the parking brake on as you are driving, but can apply the brake to assist, when necessary, without it locking on.   Handy for those 180 degree "spin-outs".

Bruce.

[Gary Christensen CLC # 21112]

Bruce,

I totally agree about the vacuum and using the brake when the car is moving (i.e. not in Park), so that it could be used in an emergency.

My issue is that there is no mechanical linkage to engage the piston.  When vacuum is applied the diaphram's piston goes "in", which releases the brake mechanism.  Conversely, when the pedal is pushed, the diaphram's piston needs to go "out", which locks the pedal into place.  It's this second action that isn't working.

As far as I can see, either pressure pushes the diaphram "out" or there should be some spring inside of the diaphram which would do it.  I don't hear anything rattling inside of the diaphram, so I'm thinking there isn't an internal spring.

On the door look mechanisms, vacuum is applied to one side or the other of the diaphram mechanism, thereby pushing or pulling the mechanical linkage for the locks.  On the brake unit, there is only one nipple that affects only one side of the diaphram.  Thus, I'm thinking that the hose itself must apply vacuum and pressure, based on somethign mechanical.

Or there's something else that I'm not seeing, but I swear I can't find a mechanical mechanism (that must be missing) that could be in play.

Gary

[Glen]

As stated the diaphragm only releases the brake.  The mechanism that “applies pressure” is the spring.  The diaphragm is never pressurized.   

[Gary Christensen CLC # 21112]

I'm still at this problem.  The spring is attached to the parking pedal and thus is involved with the pedal itself moving back and forth.  The spring is not to be connected at all to the arm of the piston and thus isn't involved in the movement of the piston.  In the "released" position of the piston (i.e. when there is vacuum applied), you can move the pedal back and forth at will without causing any movement on the piston arm.  Thus, without some other missing linkage, there is no way for the pedal action to do anything vis-a-vis the piston arm and thus pushing the pedal down can't "set" the piston such that the pedal is locked into place.

There has to be a mechanical means for moving the piston arm via the pedal, a means through the vacuum tube (i.e. pressure), or something inherent to the piston itself that enables it to automatically "reset" itself.  I don't see any mechanical linkage between the pedal arm and the piston arm on any of the photos that have been posted.  Mine looks exactly like everyone else's.  So I'm baffled.

Gary

[The Tassie Devil(le)]

....In the "released" position of the piston (i.e. when there is vacuum applied), you can move the pedal back and forth at will without causing any movement on the piston arm.... 

G'day Gary,

I am a bit baffled to.

With the vacuum applied, the Parking Brake can be applied as many times as you like and the pawl will not lock into position.   This is normal.

It is only supposed to lock on when you place the Gear Selector into Park.

Bruce.