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1985 Eldorado Biarritz Convertible, Sable Black, HT4100
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Discussion Starter #1
Hi guys, another issue: Right after I start up the car, when I step on the parking brake, it doesn't catch. I'll press it down, and it comes right back up. Eventually it catches. Shifting from Park to Drive, then trying again seems to help, and the parking brake works basically all the time after it's been running for a while. Right now it's cold in DC, so that might be a factor.

Questions:
1) I know it's a vacuum system. Does that indicate a leak or some other problem? FSM isn't much help.

2) Does a Caddy "parking brake" work as an emergency brake, say while doing 65 mph on the highway? I really don't know. Nor do I want to find out… but would like to know.

Thanks again,
Scott
 

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1985 Seville
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330 Posts
There's a vacum transfer switch on top of the steering column. If your shift linkage has slop in it it probably isn't shutting off the vacum supply to the brake. When you park try moving the lever a little until it will engage.
 

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White Diamond '03 DHS (with DTS floor shift)
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It's a parking brake, not an emergency brake. It will stop the car at 65 about as fast as throwing out an anchor.

You don't have the car in gear when you step on the parking brake do you? That would prevent it from holding. If the car is in park, then it's not a vacuum leak, but the exact opposite. It is applying vacuum when it shouldn't.
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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6,737 Posts
I agree about the gear linkage slop as a probable cause. Verify that the rod that attaches to the shift arm on the transmission has a bushing. Most do not. On my last 84 Eldo, I used an assorted bushing kit made for GM truck door hinge wear. Its part of the "HELP" brand parts at a Pep Boys store. The brass bushing slipped over the rod and I then used a wave washer and cotter pin to keep it tight.
 

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1985 Eldorado Biarritz Convertible, Sable Black, HT4100
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Discussion Starter #5
Ranger, no, not in gear. Just shifting from Park to Drive or Reverse then back to Park, then stepping on it. That seems to help sometimes, as does jiggling it a little as Omston recommends.

I've been looking through the FSM and I can't seem to find a good diagram for this. The steering column diagrams don't seem to show the shift arm/rod. Regardless, if this involves disassembling the column, I think I'd prefer to live with it. Seems like it could be a big can of worms. Would it require disassembling the column to get at that rod/bushing?
 

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White Diamond '03 DHS (with DTS floor shift)
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I don't think your problem is in the column. Either there is some mechanical part worn on the parking brake mechanism, or it is not coming out of release mode when it should. It is vacuum operated so vacuum is applied to the diaphragm when you put it in gear. When it is in park and the brake will not hold when applied, pull the vacuum hose and see if vacuum is applied. If so, it's getting vacuum when it shouldn't. Follow the line to it's source. That would most likely be where the trouble lies.
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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Re read my post. This rod is UNDER the car at the lever on the transmission! Open the hood, look at the bottom of the steering column and you'll see the shift lever linkage. It passes to a cross shaft bolted to the exhaust manifold studs then a rod goes down to the trans. That rod can be adjusted at the cross shaft assuming the bushing is in place at the trans shift lever. My bet is that bushing is missing and you have wasted motion in the linkage.
 

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1985 Eldorado Biarritz Convertible, Sable Black, HT4100
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Discussion Starter #8
Thanks guys.

Carnut, oh… I see. I actually wondered if you were talking about closer to the trans. I'll check the FSM and the car and report back. Thanks again.
 

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1985 Eldorado Biarritz Convertible, Sable Black, HT4100
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Discussion Starter #9
Was going through my old Caddy Forums threads, and saw this from a previous thread from 2013. Carnut wrote:

"Also this car is famous for the rear brakes not working! The use of the parking brake adjusts the pad in relation to the rotor surface. Lack of use causes the rear caliper pistons to seize rendering the rear brakes inop. To confirm rear brakes work, step on the parking brake firmly with your left foot and hold it down, then apply the regular brake with your right foot. Now put it in gear. Slowly remove your right foot. The car should squat and remain stopped. If it creeps forward, rear brakes are not working 100% and either need adjusted or the calipers replaced. I presume you know what you're looking for? shims on the metal back of the pad and clips that hold the back pad in the front caliper piston bore. The rear parking brake is adjusted by ratcheting the lever on the rear calipers with both cables disconnected. Explained in the factory service manual I presume you have?"

Well, finally did that test. Holding the Parking Brake down, putting it in Drive, then slowly releasing regular brake doesn't stop forward creep. That is, parking brake seems to do zero. Creeps forward at the same pace as without parking brake depressed. So my rear brakes aren't working right? Are they working at all?
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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Probably not! When working correctly, the car should squat as braked hard. It shouldn't nose drive. The only way to know for sure is to remove the rear wheels, remove the parking brake cable from the lever on the caliper and push the lever forward by hand. Halfway thru the movement, the pads should lock the rotor as you spin it with your other hand. I use a pair of needle nose vise grips to pull the cable rearward to pull it over and out of the lever slot. If the pistons aren't seized in the caliper, simply moving the lever forward/ back should within a few strokes take up the slack and the pads should grip. If not you need 2 rear loaded calipers. "loaded" meaning pads installed. Report back with your results prior to replacement.
 

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1985 Eldorado Biarritz Convertible, Sable Black, HT4100
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Discussion Starter #11
Thanks Carnut. That sucks. I'll walk through the process in the FSM and decide whether I want to take a stab at this. I'm reluctant to do brake work myself. But I'll give it a shot if I think I can do it. I've been meaning to have a pro take a look at the mystery grind in my front brake anyway, so I might have him take a look at both.

The front brakes provide the majority of braking power, right?
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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Yep! The rear calipers have hard metal lines not flex hoses so its a bugger to get the lines off and back on, then you must bleed the brakes. The parking brake cables MUST be adjusted according to the FSM. IMO not the easy pad replacement like most cars. The grinding might be because the front brakes are doing too much gripping, you've glazed the rotors or.....you have semi metallic front pads which tend to grind normally.
 

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1985 Eldorado Biarritz Convertible, Sable Black, HT4100
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Discussion Starter #13

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1985 Eldorado Biarritz Convertible, Sable Black, HT4100
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Discussion Starter #14
This may be a dumb question, but can I test to see if the rear brakes are working by putting the rear end up on jack stands, with blocks in front of the front tires, and spinning the rear wheels, then pushing the brake pedal, and see if they stop spinning?
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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Sure you can! But its easier to simply hold the car in gear with your left foot on the park brake and right foot on the brake pedal, then slowly release the brake pedal. If the car creeps forward the rear brakes don't work.
 

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1985 Eldorado Biarritz Convertible, Sable Black, HT4100
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Discussion Starter #16
Thanks again, Carnut. I figured there might be a problem with the parking brake mechanism, but the rears might work independent of the parking brake, i.e. using the regular brake pedal. So if the parking brake doesn't work, then depressing the regular brake pedal won't do anything with regard to the rear brakes?
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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The parking brake "mechanism" is a lever that rotates the piston within the regular rear brake caliper. If its not used the caliper pistons never rotate and seize within the caliper eventually so no grip from the rear brakes! Unlike my Mercedes. Within the rear rotor my car has a little set of drum brake shoes.
 

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1985 Eldorado Biarritz Convertible, Sable Black, HT4100
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Discussion Starter #18
Hey Carnut, I have an appointment with a garage to work on the rears next week. If the rear brakes are seized, and I assume they are, is the fix simply freeing up the pistons? Or do I have to replace the calipers, pistons, etc? Thanks!
 

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White Diamond '03 DHS (with DTS floor shift)
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It depends on what the problem is. It could be a seized parking brake cable. That is more common than anything else.
 

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I explained this earlier! If.... after moving the lever back and forth on the caliper (parking brake cables removed) and the piston does not rotate out, you need 2 rear calipers. Parking brake cables? sure they can seize, but that's easy to diagnose. Remove the cables from the caliper lever and verify they slide back and forth.
 
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