1970s 1979 Fleetwood Brougham D'Elegance braking question

[guyrobert]

My 79 Fleetwood with 29K original miles is having a braking issue,
I have already had the master cylinder replaced and the pads done.
The pedal is very spongy, and the brake light is on all the time.
The problem started last week when I was on a small Island with lots of steep small hills
The rear brakes were getting hot and the fronts didn't seem to be doing their job.
There is lots of fluid in the reservoir and no obvious signs of leaks or seepage from the wheel cylinders
I am thinking it may be the proportioning valve?
Any other suggestions?
Thanks in advance
Robert

[jagbuxx #12944]

I was a service advisor at a Dallas area Cadillac dealer 1979-1981, the 4 wheel disc system-rear calipers were problematic and contributed to the spongy feeling brakes at the time. 40 years later now, not so sure

[TJ Hopland]

Was the master cylinder and pads replaced before or after this problem started?

Do you know when the hoses were last replaced?  Hoses can have internal failures that kinda act like check valves and can cause the brakes to drag.

The rear calipers have several moving parts and extra seals that live inside in the brake fluid that were not known to be the most reliable.

[V63]

Check the rear calipers that are probably having an issue with the emergency brake in cooperated into them, very common issue with the ratcheting feature and replacing the rear pads.

[Dave Shepherd]

Correct, failure to use the e brake frequently can cause a low pedal.

[TJ Hopland]

That was one reason I was asking about when the pads were replaced in this saga.  If things were fine till the pads got replaced perhaps the person doing the work didn't do it correctly.  The calipers could have been in bad shape to start with and should have just been replaced.  They could have damaged them returning the pistons for the new pads.  They could have just not adjusted them properly.  Out of adjustment doesn't explain why they are getting hot unless that was before the pads were changed then we are back to the calipers were bad and should have been replaced.

The MC I am curious about because maybe the new and old are not an exact match and the piston isn't fully returning and that is what is causing all the current issues.   

[Chopper1942]

To often, today's brake jobs are just a pad slap and they did not bleed the brakes after replacing the MC. Only bled the MC.

I have a 79 ElDorado and when I got it in the early 80's it had lousy brakes. These are the steps I used and use on other vehicles to make a solid pedal.

If you or a friend have the tools, do the following.

Get the car up on jack stands. Before you remove the wheels, see if you can turn the rear wheels by hand or do they drag. If they do not drag, get in and start the car and apply the brakes several times. get out and try to turn the wheels, If they now drag, there is a restriction in the hose or hoses or the calipher seals are not pulling the piston back.and the hoses or caliphers need replaced. Remove the wheels. Crack the bleeder screw on the calipher that is dragging. If fluid squirts out and now you can turn the axle easily, the hose for that wheel is bad.  As old as the hoses are they should be replace anyway. If it still drags, either the pads are misadjusted or the calipher seals are bad. and the caliphers need rebuilt or replaced.

Get out the OE FSM and properly adjust the rear brakes. The rear pistons should have notches sually 90° apart and the pads should have a tang that goes in the notch. If the pads don't have the tang, check and see if the outside pad has a tang. If neither pad has a tang, it will be difficult to keep the rear pads in adjustment.

Unlike self-adjusting drum brakes, which adjust when you back up and apply the brakes, The rear pads maintain the correct clearance with the rotor by applying the parking brake. Each time the park brake is applied an internal screw turns to maintain the proper adjustment (clearance). Because most people do not know this and normally do not use the park brake, the pad clearance increases and this causes a low pedal. Depending how much you drive the vehicle, every once and awhile you need to apply the park brake several times after a drive.

With the pads properly adjusted, remove the park brake cable and spring from the park brake lever. Move the lever from the stop to the applied position. The clearance should be 1/16"-1/8". If more, you need to remove the lever, reinstall the nut a few threads, and ratchet the park brake shaft back and forth a few time, reinstall the lever, and check the clearance. Do this until the lever has the proper clearance.

If the front brakes are not working properly, the rear brakes are doing all the stopping and are going to get very hot. Crack the bleeder screw on each calipher, one at a time, and let the fluid drip out for awhile. Maintain the fluid leavel in the MC. Close the valve and do the same on the other side. Gravity bleeding should remove any air trapped in the system.

MAKE SURE THAT THE BLEEDER SCREWS ARE AT THE TOP OF THE CALIPHERS.

Now do the same on the rear caliphers.

Get in and start the engine and apply the brakes. If the pedal is low or spongy, do a manual bleed with either a vacuum bleeder or have someone, with out the engine running, pump up the brakes and you crack the bleeder screw. Do this until there is a solid stream of fluid with no air bubbles.

Start at the lf front calipher, next the rt front, then the lf rear and finally the rt rear.

I forgot to mention to grab each calipher and see if you can move them in and out. They should slide easily since they have just been off.  Also, lube the abutment clips, edges of the pads where they contact the calipher brackets, the backs of the pads, and slide pins with silicon brake lube.

I think Icovered everything. If any questions, post back and I'll try to answer them. Good Luck!

[guyrobert]

Lots of great suggestions here, thanks very much for that.
The car did have the issue before I took it in for the brake work at my local garage (one of the few here that will still work on these cars)-Fred's automotive. They instructed me to engage the emergency brake every time I stop and park the car.
At present this does not seem to be making a difference. They did install pads that are supposed to stop the car quicker and those do create a lot of dust, but the problem is for sure not "fixed"
BTW the car is in very good condition with no rust and the hoses and belts are pliable, I did have Fred's check the brake hoses and I thought they might be an issue after all this time but they checked out fine.
My 79 Phaeton coupe stops on a dime compared to the Fleetwood, although when I first bought it with 22K original miles the brakes were good.
Unfortunately there is a city bylaw preventing working on your car on the street here and Fred's has a 3 week waiting list so it maybe some time before I can get this issue solved.
The reason I was asking about the proportioning valve is in my research that was mentioned as a possible culprit and if it needs to be replaced it would be best to have it on hand for the mechanics
Thanks again for the advice
Robert

[TJ Hopland]

It does seem like a good sign that they told you to use the parking brake.  That implies at least someone there has some level of knowledge about how this style of caliper/parking brake system works.  Now was that just the desk person and he didn't tell the person in the back anything and he was back there with the 100 ton press trying to get the pistons to retract?  Ya never know these days.

Was the pedal and performance reasonable when you first picked it up from the shop?   And it got worse?  Or hasn't it changed really at all before or after the pad repair?

Was the MC repair at the same time as the pads?

Was the hot issue both before and after?


Prop valve is possible but isn't that common of a failure.  Brake light being on does indicate that currently the prop valve is shifted one direction or the other due to an imbalance in the system.   That can happen during bleeding or a failure in a line but usually corrects itself as the system is bled and starts to return close to normal. 

Hoses can look fine on the outside but have internal issues and whats wacky is the broken down internals can act like check valves so the 1000 psi of braking pressure can get past it but the single to 3 digit pressures that should be returning to the MC to let the pads retract slightly can't get past it sometimes at all or more often than not fast enough.  Let it sit for a day and maybe it will bleed down and work till you hit the brakes again sort of thing.

[guyrobert]

Thanks again for all of the detailed help, my garage is pretty good, they are all mechanics and there is no "person" at the front desk.
The MC and the pads were done at the same time, along with the general service of the brakes.
They were ok when I picked the car up but still not as good as when I first bought it.
The heated rear brakes were hot and you could smell them when I was driving around Saltspring Island on the weekend, it has some very steep small hills and gullies (16% grades) and that is when the brakes really started to act up.
It has been several days now and the brakes are still spongy and not good. The light stays on all the time.
I have activated the parking brake several times in a row and tried braking hard in reverse (which a friend suggested) and no improvement at this point.
I have had the MC, the front rotors and all the pads replaced.
Robert

[Seville Life]

Good morning Robert, Paul here from England, currently touring France, now in Burgundy where the great wines are made. Internet connection is rubbish so I'll keep it brief.

These 4-wheel disc brakes can be made to work right but it takes effort. Yes it's the rear ones that are the problem. Yes in the day customers complained of low pedal pressure and flickering brake warning lights. YES the chap below is 100% about it being directly related to the parking brake being used all the time.

We get used to forgetting the parking brake often, with these it is critical.

Every time you apply the parking brake it adjusts the pads incrementally. this keeps your service brake pedal feeling right and applies the rear brakes effectively.

If you don't use the parking brake (sorry I'm repeating the other guy's explanation) the pads become further away from the rotor because they are not adjusting, the rear brakes are less effective and the pedal is dropping lower all the time, eventually causing the brake warning light to flicker.

I run a '78 Seville Elegante and know these rear brakes well.

I would suggest that first of all you read through this document. It is a tome but a typically superb piece of Cadillac Service Department work. They were being asked by dealers why the brakes on customer's cars were proving difficult to get right. This analysis explains what to do.

https://www.modifiedcadillac.org/documents/1970s/1978/1978%20Brougham%20Seville%204%20wheel%20disc%20diagnostics/

Sadly we can't get the complex piston as a part any longer and it is the mysterious goings on in these that is causing the problem. You can open these but it requires care, failing brakes is no fun.

I've seen folk simply tighten the parking brake cables, DON'T, if the lever arms are off the stops you could cause part brake application permanently and all the grief that brings.

The other chap is also correct that regularly flushed brake fluid helps, our fluid is hygroscopic, ie, it easily absorbs water and water causes havoc inside the rear piston mechanism. Let's face it, none of us do this, but Cadillac tell you to flush your brakes every 24,000 miles or 2 years (1978).

I'll drop you my details on a direct message. Paul

[Chopper1942]

TJ is correct about the prop valve not being the issue. In all my years in the business, I have never replaced a prop or combination valve for a braking issue. I have only installed them when changing from drum brakes to disc/drum or disc/disc brake systems on older street rods or hot rods.

I can almost guarantee that either the rear pads are not adjusted correctly or there is an issue with the piston/adjusting screw.

When you take the car back to Fred's, act like you are un-informed about how the brake pads are replaced and specifically about how the pistons are retracted.  If they say they used a C clamp or a retractor tool on the front pistons, that is OK. If they say they did that on the rear pistons, they probably damaged the park brake mechanisim inside the calipher.

Tell them that you talked to an aquaintance about your braking problems and that he is a GM World Class Technician and has been working on these since they wer first introduced and these are his suggestions of sone things to check.

1.  Ask them to check pad adjustment and the park brake lever clearance (reference the previous post).
2.  Then remove the inside rear pad, remove the park brake cable and spring, and then ratchet the park brake lever
    like your are applying the park brake.  The piston should move out slightly everytime he moves the lever. If it
    does not, you will need to install a rebuilt calipher.
3.  The park brake lever adjustment is critical for maintaining proper rear pad adjustment. Even if new caliphers
    are installed, you can not just install the lever and call it good. There are 6 flats on the screw and lever. If
    it just put on without setting the clearance, you will continue to have a low pedal and lousy brakes.

My suggestion as is TJ's is to replace all the brake hoses even though they look "good".

If everything is done properly, you should have great brakes.

I am somewhat concerned that they would let the car go with brake issues just after they worked on it. Also, that they are putting you off for 3 weeks to look at their comeback.

[Eric DeVirgilis CLC# 8621]

The brake warning light should never illuminate if the brake system is functioning normally. Otherwise the pedal in these is never as firm as it is on models with rear drum brakes. Agreed with all the points raised above regarding the importance of periodically using the emergency brake to keep the rear calipers in adjustment.   

[guyrobert]

OK all this is very helpful, I have scheduled another visit to Fred's it takes 3 weeks to get in as they are always really busy.
Just to clarify the brakes were working ok when they did the last adjustment and they were ok (not great) when I took it out of storage last week to go for the Island drive, it was going up and down the steep short hills that things started acting up and the rears got heated, the light came on and you could smell the rear pads.
For Paul in the UK thanks for the link and enjoy you time in Burgundy, I am in the wine business and will be in Bordeaux in a few weeks
Thanks again for all of the informed replies
Cheers Robert

[guyrobert]

I have an update,  Got a call from Fred's today and they have found that both parking brake cables were kaput in addition both rear calipers need replacement
Parts will arrive next week so with any luck I will be motoring (weather permitting) in a couple of weeks.
I also had them add another NOS horn as it only had 2 originally
Cheers Robert

[Seville Life]

You will your mechanics to go through that document I sent over regarding setting up the new calipers?

If they are not set up correctly at the start the service brake will always be less effective as will the parking brake.

The action of 30 pedal presses for both, in the right order sets up pad-to-rotor tolerance then sets up the mechanism inside the rear piston that establishes the parking brake.

The caliper lever arm must always rest on the stop, it's easy to over-adjust them. Have fun. Paul

[shadetree39]

Ive replaced the entire service brake system on '76 Eldorado, except The rotors which are well within specs. The issue is inability to bleed them . I've run at least 20 oz. thru the RR alone still getting bubbles with fresh fluid each time. I'm using a vacuum pump now as my assistant (wife) is getting tired of "pump", "hold", "let up". Ive bench bled the the MC twice and I also replaced with a 2nd new one thinking maybe it was a bad . No leaks anywhere and I have a plug in the sensor that keeps the prop. valve centered.
The parking brake seems ok but the LS return spring on the caliper is a little weak.
I've set and released the E brake many times and am wondering I'm getting the adjustment as described in this thread. the brake arms don't return to its stops consistantly.
The arms locate on a hex on the screw so if I back it off to the next hex it seems to loose. The only solid line that I didn't replace was the one from the rear sump with all the loops. The hand and the vacuum release both seem to work OK but pedal doesn't return all the way.
I've never tackled anything as complicated as this car and really am grateful for all help provided. 

[Seville Life]

The rear disc brakes on a '76 Eldorado are slightly different from those on the '77/'79 Seville and Brougham. The superb Cadillac Service Department service booklet written in '78 does not cover the Eldorado.

Surely it is covered in the red '76 Cadillac workshop manual? It is explained in the white and blue '77 Cadillac service manual, you need one of these.

If the lever arm does not return to the stop on the caliper consistently the workings in the pistons are at fault. It could of course be the Archimedes screw that passes through the caliper body in binding, old age and rust. Are your calipers original, new or rebuilds? You do need a Cadillac book.

[shadetree39]

I do have that shop manual and its great..couldn't get anywhere w/o it. Also have both FI manuals and a Fisher body manual. Not much coverage of that parking brake issue and pretty much std bleeding stuff.  I'm awaking this car from a 30 some odd sleep. 
It was suggested to air bleed over a few days so I'm giving that a try .

[TJ Hopland]

If you really think its a bleeding issue start trying to bleed in other places.  If you got air trapped somewhere in the middle maybe bleeding somewhere other than the ends will help.