[HWYSTR455]

One more thing, the brake pedal arm has 2 holes on it for the master rod, one for power, one for disc (if the year the car was made was available with discs).


.

[NeighborsComplaint]

I've tried both the upper and lower hole positions in the pedal arm before. Since day 1, the only way the car will stop is with the pedal stop backed almost all the way out to where your knee hits the steering wheel when trying to apply the brakes. The pedal travels forever doing nothing and doesn't begin stopping the car until it's an inch and a half off the floor. If I adjust the pedal, lower, I lose the brakes altogether. The lower pedal hole is slightly better than the upper hole as the geometry results in more MC piston travel for equivalent pedal travel.

I've checked the rear caliper preload multiple times, bled the system with a mighty vac multiple times and even used a master cylinder pushrod gauge to measure the pushrod length. The measurements show the pushrod length required is standard 2-5/8" like most GM's using a shallow cup master cylinder (for power brakes).

Last year just before putting the car in storage, I mounted a deep cup master cylinder intended for manual brakes and the corresponding longer master cylinder pushrod (3-15/16"). The pushrod was too long and compressed the master cylinder making the brakes drag but actually made the car stop like a normal car. I left it alone and put it away in storage last fall and when I got it out this spring, all 4 brakes were nearly completely locked. I could hardly move the car as it literally snow plowed straight ahead on loose surfaces with the brakes locked up.

I swapped on an OEM style 1-1/8"master and the shorter pushrod and was rewarded with the same ****ty brakes as before and a hood I can't close. There's some real progress there. As I said, I ran a string from fender to fender and saw it wasn't going to clear. I have a fiberglass hood and it's pretty obvious when it begins to bulge right over the master cylinder when slowly lowering it.

I am at a loss for an explanation as to why my pedal continues to travel nearly to the floor before the brakes begin to activate and provide so little braking pressure that the car cannot be driven except when "tricked" into working by depressing the plunger in the master cylinder with longer pushrod partially applying the brakes.

The pedal is rock hard before starting and then drops to the floor once the engine vacuum activates the booster. The booster is not the issue.

[Scarebird]

Refresh my memory - what type of calipers are in the rear?

[NeighborsComplaint]

Originally Posted by Scarebird

Refresh my memory - what type of calipers are in the rear?

Cadillac Eldorado with integral parking brake. I've adjusted preload to the specified 1/8" maximum travel before pad contact.

[HWYSTR455]

How did you measure pushrod length/engagement? With the proper measuring tool?

That sure sounds like a pushrod/cup mismatch to me. Or maybe a booster issue.

What kind of booster and where did you source it? And has it done that since the new booster?

Can't tell you how many 'new' boosters I had issues with, but to say it out loud, it's hit or miss with the aftermarket boosters.

And, maybe the booster brackets on it are the incorrect ones? Was the OE one the same angel?



.

[HWYSTR455]

https://www.amazon.com/Booster-Adjus...iABEgJAnvD_BwE

[NeighborsComplaint]

Originally Posted by HWYSTR455

https://www.amazon.com/Booster-Adjus...iABEgJAnvD_BwE

That's the gauge I used to check the pushrod length. There is no mismatch.

The fact that the brakes improve with the wrong (longer) pushrod takes up eliminates the excessive pedal travel to the point of the brakes dragging tell me there is still something wrong with the "gap" (distance between retracted eBrake lever and stop) in rear calipers.

I am going to reinstall the shallow cup master that clears the hood and the corresponding pushrod. After bleeding I am going to pinch off the rear brake hoses with vice grips and see how the brake pedal responds. If the pedal firms up and travel is returned to normal, then I know the rear calipers just don't work and will have to look at alternatives.

I read an interesting fact that many loaded Eldorado calipers are fitted with D52 pads (cheaper) instead of 5he correct D122 pads. The difference between a D122 and a D52 is slight, but significant: D122 pads have a locking feature that keeps the piston from twisting when the brake is applied. D52 pads do not. This lack of a locking feature can cause the parking brake to slowly release which causes a loss of the preload setting and results in excessive piston travel beyond the capacity of the master cylinder. This might explain why I can initially get a decent pedal which just drops away to the floor away after a few stops. I don't have any idea if my pads had this anti-rotation tab as the pads were loaded in the caliper and I never removed them to inspect.

[Scarebird]

Originally Posted by NeighborsComplaint

Cadillac Eldorado with integral parking brake. I've adjusted preload to the specified 1/8" maximum travel before pad contact.

When you engage the parking brake doe it actually hold the car on a slope?

[NeighborsComplaint]

Only immediately after adjusting preload. Drive it around the block and no.

I was reading about these calipers on Jeg’s website. According to them you must set the parking brake every time you park the car or you lose the preload (you just spent hours adjusting) and excessive pedal travel and loss of braking pressure results.

I just ordered a pair of ‘81 Eldorado front calipers and will install them in place of rear ones I have now. At least I can count on the f’ing car stopping even though I give up the eBrake.

I’ll update on the result.

[HWYSTR455]

True about the e-brake, maybe not every time you park the car, but should frequently operate the e-brake.

Speedmaster just started repopping the metric calipers, as an FYI:

https://www.speedmaster79.com/GM-Rea...ide-7-16-Inlet

The calipers were at one point hard to get, and only remanufactured ones were available. Quality was spotty.
.


.

[HWYSTR455]

They also do a rear disc kit for $235:

https://www.speedmaster79.com/BRAKE-CALIPERS

.

[Scarebird]

Originally Posted by NeighborsComplaint

Only immediately after adjusting preload. Drive it around the block and no.

I was reading about these calipers on Jeg’s website. According to them you must set the parking brake every time you park the car or you lose the preload (you just spent hours adjusting) and excessive pedal travel and loss of braking pressure results.

I just ordered a pair of ‘81 Eldorado front calipers and will install them in place of rear ones I have now. At least I can count on the f’ing car stopping even though I give up the eBrake.

I’ll update on the result.

The fronts may not fit; too big (2-1/8" vs. 2-1/2").

Do you have an extra caliper lever laying about?

[george kujanski]

Using the e brake regularly rachets the piston out to take up the clearance between the pads and rotor due to wear.

Had those on 2 eldos and currently on an Allante.

George

[NeighborsComplaint]

Originally Posted by Scarebird

The fronts may not fit; too big (2-1/8" vs. 2-1/2").

Do you have an extra caliper lever laying about?

I just ordered some Wagner rebuilt metric calipers for the rears. If all goes according to plan, I'll have 2 complete Eldo calipers shortly. I'm too old to be crawling under cars so I have to find s shop to do the swap and bleed them. You know how that goes. Most shop won't install your parts and won't order any parts not specific to the vehicle. One shop already declined saying "The opnly way we'll touch it is if we order the parts and restore the brakes back to the original OEM condition, no aftermarket parts.
Honestly, at this point, I'm about at the point that it doesn;t sound all that unreasonable. At least the car could be driven.

[NeighborsComplaint]

As a matter of clarification, the metric calipers I ordered are Eldorado fronts which I plan to install in place of the rears and give up on the ebrake.

[Scarebird]

An easy tell if the rear caliper gap is too much is to clamp off the hose from the frame to the axle and go for a short drive. If your brakes are back the calipers are the issue.

I will look some more, but I made a tool to adjust these calipers, essentially just a lever bent up so you can spin the shaft 360° with a non-locking nut and tighten up the clearance: 0.125" is WAY too much.

[NeighborsComplaint]

Originally Posted by Scarebird

An easy tell if the rear caliper gap is too much is to clamp off the hose from the frame to the axle and go for a short drive. If your brakes are back the calipers are the issue.

I will look some more, but I made a tool to adjust these calipers, essentially just a lever bent up so you can spin the shaft 360° with a non-locking nut and tighten up the clearance: 0.125" is WAY too much.

That's what I said I was going to do to test the rear calipers in my post #27 so that's old news. I went a step further and disconnected the rear brake line at the proportioning valve, installed a prop valve centering tool and then capped off the rear brake port since I will be driving it to a shop (when I can find a competent one). The front brakes worked fine so it's all in the preload of the rear calipers. Again, I can't do this kind of work any more due to my physical limitations from a form of paralysis.

I visited several shops today and not a single one had a clue what I was talking about. I told them all I had an '81 Eldorado with 4 wheel disc brakes and needed the parking brake preload adjusted. I've learned to not say I have a '71 GTO with a rear disc conversion because the shops just roll their eyes and point you towards the door.

Not a single shop knew that Eldorado's had a disc brake option much less any idea how to adjust the ebrake. Two of the shops I visited insisted I have drum brakes and must be mistaken.

I bought the Eldorado front calipers with the understanding (from the Cadillac Forums) that both front and rear are metric spaced and are interchangeable of course without the parling the parking brake mechanism. I hope my research is correct.

[Scarebird]

Originally Posted by NeighborsComplaint

...I bought the Eldorado front calipers with the understanding (from the Cadillac Forums) that both front and rear are metric spaced and are interchangeable of course without the parling the parking brake mechanism. I hope my research is correct.

Depends on the kit - ours would not accept the Metric fronts.

[NeighborsComplaint]

Yeah, this will be a crapshoot. I have no confidence that the shops in my area are capable of setting the preload on my rear calipers so I am planning on just replacing the rear calipers and giving up the parking brake.

I replaced a rear caliper a few years back and used an OEM replacement so I know I have metric pin spacing (5-1.2") as do the front calipers I ordered which typical GM Mid-sized Metric calipers.

At least that's the plan anyway.

[HWYSTR455]

Why not just cycle the e-brake a bunch of times? You can actually feel the e-brake travel being taken up as you do it.

If it's not operating properly, and the calipers' e-brake function is boogered, you have to at least remove them and diag the cause, correct or replace. I know crap can build up in the adjusting puck/piston, and/or sometimes hang when they have been sitting a long time.

Like I said before, I've had a lot of repop eldo calipers that were junk right out of the box, and am happy to see that new ones are being reproduced. They are not much more than the repops at $99 each.

That's pretty scary the shops around you don't know what you're talking about, I would never go back to any of them, and would travel further to find one that is good. Or have a forum member come and help you.



.