: New brake pads fading after 15 m.i. city driving, return to normal when cool?



Benzilla
04-13-13, 08:21 PM
I'm having a perplexing problem with the new pads I installed about a month ago ('79 DeVille): Yesterday I was running some errands downtown, I was probably driving in stop & go for about 15 miles round trip without stopping for about 45-60 minutes (probably the longest stretch since installing the pads). When I was a couple blocks from home, I was rolling up to a stop light and noticed the brakes didn't have much stopping power. I heard groaning from the front brakes as I stopped. Kept getting less feeling from the fronts as I continued home, it felt like I stopped in the driveway with only the rear brakes. I didn't notice a directional pull, just no front stopping power. It felt like the time I overheated my brakes on a long winding mountain road in my Brougham.

About 30-60 minutes later, I took it for a spin around the neighborhood, and the brakes felt normal. :hmm:

The pads are brand new Ceramic Wearever Platinums. The car just got out of the shop from having the 3 flex hoses replaced & lines bled. I was wondering if I somehow contaminated the pads while installing them. I tried hard to keep them clean, but it's possible. I replaced the flex hoses & bled lines because I feel like the pedal has more travel than it should, even when compared to my other '79. Rear shoes have plenty of life. I have never replaced the calipers, but they don't show signs of leakage.

Thoughts? My service manual doesn't say anything about fade-away, but otherwise I match the symptoms of contaminated pads. They haven't felt grabby, though.

Thanks! :)
-Ben

csbuckn
04-13-13, 11:48 PM
With reading your post, it seems the parts that would cause this are new so maybe your have sprung a leak at a connection or still have air in the system. My pads fade as I drive but not much.

Benzilla
04-14-13, 01:41 AM
But if I had a leak, or air in the ststem, wouldn't the brakes just suck all the time?

csbuckn
04-14-13, 02:56 AM
Yep. So has this been going on for a month now or was the downtown run the first its happened. Brakes feel good the next morning?

cadillac_al
04-14-13, 10:01 AM
That sounds strangely similar to a proportioning valve malfunction that normally affects the rear brakes. Usually after you blow a brake line. That wouldn't be intermittent though. I would do more careful testing but if it really feels like you are stopping with only the rear brakes, you could do the normal tricks like tapping on that combo valve and if that doesn't work, possible bleeding the rear brakes will reset it. This is just my theory at this point, I'll think about it some more.

deVille33
04-14-13, 10:47 AM
I think al is on the right track. Sometimes, when working on brake systems, you get a little air trapped in the directional valve, and the imbalance can cause the valve to seat in one side or the other. I have had to bleed the line going to the back brakes at the directional valve outlet line to remove the air.

jayoldschool
04-14-13, 12:30 PM
I'm going to agree. Sounds like a bleeding issue. I recall that you just bled the fronts, correct? I would get back at it and rebleed, and consider doing all four.

Benzilla
04-14-13, 02:30 PM
Actually, I ended up taking it to a shop & having all new flex hoses put on, and all lines bled, as it says. So I'd be very upset I'd it was a problem with the $120 bleed job. I only use the shop for emergencies or because of a lack of time / tools. In this case all of the above. They were also supposed to check everything while it was on the lift (one can only see so much on concrete).

So, nobody thinks it sounds like pad contamination? Hmm.

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Ps, that trip was the first time they faded like that. If they had pulled that little trick sooner, I'm sure y'all would have heard about it. The brakes on this car have always seemed to have too much travel, so that's nothing to do with recent developments. But before I replaced the pads my self, and got the lines bled by the shop, I never worried about my car not stopping. Now I do.

jayoldschool
04-14-13, 03:11 PM
The brakes on this car have always seemed to have too much travel

My Caprice felt like this. All my other cars have a high, firm pedal. The Caprice took a lot more pedal to stop. I finally discovered a failed rear wheel cylinder. Worth a look.

The Ape Man
04-14-13, 04:15 PM
Yer not mentioning spongy pedal. If it isn't spongy and just takes more pedal effort for same stopping power as when cold it could be overheated linings.

The rear brakes give pedal feel on these cars. If they are not adjusted properly the pedal will have excessive travel. Sometimes mek-a-niks over-adjust them to give that high pedal feel.

You could be suffering from the rear brakes overheating and fading or the front. Either will show itself as hot hot hot after a drive. Add the real axle bearing slop problem inherent to this car and rear brakes can overheat even when adjusted properly.

Benzilla
04-14-13, 06:44 PM
I'm not sure I've ever felt what's described as "spongy" pedal. I just ended up having to push the pedal pretty much to the floor to coast to a slow stop once it was heated up a bit. When limping home the last block, I smelled something like hot brake fluid (sweet & almost smokey), but I didn't see any leaks under the car or around any lines I could see without popping a wheel off.

Right before I test drove the car an hour after the incident, with the car running I repeatedly smashed the living hell out of the brake pedal trying to make something break if it was going to! It can't be a leak, because once cool, pedal feel was normal for the car like nothing had happened. Before the new pads and bleeding, I could drive this thing 200 miles nonstop without ANY brake fade. That's why I was wondering about contaminated pads.

What could be making the new pads overheat? No grabbing, good pedal return.. My driver's side rotor is slightly warped, rotors were next on my list, but I have to prioritize expenses right now.

Rear brakes stopped the car just fine with the worn out old front pads. :-/ This (the bad fade away) isn't something that came on slowly, it only started just now after the brake work.

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I should add: though the new pads seem to slow the car quicker, it consistently seems to take more brake force to keep the car stopped at a light. I've found myself coasting & had to push the brakes harder than I did before the new pads to keep it from creeping forward. That's really why I had all the brakes bled. No difference after bleeding. This is why I asked about possible contamination during installation. Kept my hands wiped off and tried not to touch the surface, but I had a bitch of a time getting the pistons to compress enough for the new pads, so lots of test fitting & handling was done.

The Ape Man
04-14-13, 06:58 PM
The pedal should not get near the floor unless there are big problems.

Almost soulds like the master cylinder might be weak. That will give you a sinking feeling. Stop at a light and it takes more pedal depth to keep the car from moving. This does not account for any smells though.

Master cylinders can be weak with only slight or even no indicatin of leaking.

cadillac_al
04-14-13, 08:08 PM
I have never seen a mechanic yet that was anywhere near as clean as me when butting brake pads on. I see so many greasy hand prints on rotors and pads and they seem to live ok or nobody notices. It sounds like you were clean enough putting them on Ben.

You would think if you paid to have them bled that they would be bled right. I would say just wait and see what happens the next couple days. If they still act up and you mention it to your shop, they will probably check it out for you or bleed them again for free. I would think the reason they charge the big bucks is because they are somewhat liable if the brakes fail. If they don't stand behind their work just casually mention "gee I hope I don't get in an accident because of this" and a light bulb should go off upstairs. Hopefully it will never come to that. This is all hypotheical so far because we aren't sure it's a bleeding problem yet. They may try to blame you for screwing up the brake job somehow

I just noticed you did mention that it did have a longer pedal travel than your other 79 so it may be the master cylinder after all. I guess you will have to do some more driving and diagnostics for a while. Good luck.

deVille33
04-15-13, 10:23 AM
Common for this to happen, after upgrades or replacing linings or other parts, the master will show it's weakness. The basic system becomes more effective, any of the seals that have wear will cause fluid to transfer from one stage to the other. At times the seal may hold, but as the seal wears, it will leak down more often. Rebuilt units are cheap, but I prefer reman. units from Cardone, and top of the line new units from EIS.

The Ape Man
04-15-13, 11:01 AM
That is a good explanation.

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Common for this to happen, after upgrades or replacing linings or other parts, the master will show it's weakness. The basic system becomes more effective, any of the seals that have wear will cause fluid to transfer from one stage to the other. At times the seal may hold, but as the seal wears, it will leak down more often. Rebuilt units are cheap, but I prefer reman. units from Cardone, and top of the line new units from EIS.

jayoldschool
04-15-13, 12:14 PM
Get the rear wheels off, check for leaking wheel cylinders first! The light won't come on with one leaking UNTIL the master runs dry. This would certainly explain the pedal to the floor, and the smell with no visible leak. You might even be able to see the leak simply by looking at the backing plate at the bottom of the drum. That's how I knew I had a failed cylinder. I had actually crawled underneath to bleed, having similar symptoms to you...

drewsdeville
04-15-13, 09:47 PM
If it smells like hot brakes and they fade quickly, I'd consider seized calipers. They always show their true colors at pad replacement, when you compress the piston back into a rusty bore - thus a sudden malfunction. Did the pistons seem unusually difficult to compress? Is the brake fluid dark or muddy? This only began happening after pad replacement, not before, correct?

jayoldschool
04-16-13, 12:01 AM
It would pull to one side with a seized caliper.

Benzilla
04-16-13, 01:21 AM
So I took the car out for a couple of short trips today. Drove down to an ATM & back (probably 4-6 miles round trip), and later drove to the store (3-4 miles one way, cooled between trips). Brakes felt fine again. Drove aggressively & had plenty of pedal response. Checked the wheels for heat. Rears were cool, driver front warm, pass side front slightly warmer. Haven't had a chance to pop the wheels off again yet. Will do tomorrow.


Get the rear wheels off, check for leaking wheel cylinders first! The light won't come on with one leaking UNTIL the master runs dry. This would certainly explain the pedal to the floor, and the smell with no visible leak. You might even be able to see the leak simply by looking at the backing plate at the bottom of the drum. That's how I knew I had a failed cylinder. I had actually crawled underneath to bleed, having similar symptoms to you...

Jay, will check that too. Checked the right rear wheel already, just looking for general pad condition. It looked great, will check the other side. Question though, if it was leaking, how could the brakes return to normal like they did? Would the combination valve just pull fluid from the front or what?


If it smells like hot brakes and they fade quickly, I'd consider seized calipers. They always show their true colors at pad replacement, when you compress the piston back into a rusty bore - thus a sudden malfunction. Did the pistons seem unusually difficult to compress? Is the brake fluid dark or muddy? This only began happening after pad replacement, not before, correct?

Old brake fluid was dark & nasty before the flush. Calipers were a pain to compress, actually had a sore hand for a day or two.. Driver's side was hardest to compress IIRC. Haven't noticed much if a directional pull. it seems to wander *slightly* to the right at times, but really assumed it was just the original (kinda worn) front end responding to the slope of the road, lol!

Thanks so much for all the tips!

-Ben

drewsdeville
04-16-13, 08:13 AM
It would pull to one side with a seized caliper. I'm suggesting that both fronts aren't releasing when off the brake pedal, not one.

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Old brake fluid was dark & nasty before the flush. Calipers were a pain to compress, actually had a sore hand for a day or two.. Driver's side was hardest to compress IIRC.

Thanks so much for all the tips!

-Ben I'd say that's enough evidence to check them out. A properly working caliper will compress with little effort, and the fluid condition suggests that the calipers and wheel cylinders may not be in good condition.

The Ape Man
04-16-13, 11:24 AM
Exactly how did you compress the caliper pistons?

A weak master cylinder can work OK for a while then allow the pedal to sink. Sounds more and more like your problem.

Benzilla
04-16-13, 04:39 PM
I used this tool to compress the pistons. I didn't have a C clamp big enough on hand, thought I might as well get the right tool for the job. When I had trouble, I just assumed I wasn't getting enough torque with the little 'X' handle on the tool...

http://i24.photobucket.com/albums/c40/Cadillac_guy/2491_zps1e38c13e.jpg (http://s24.photobucket.com/user/Cadillac_guy/media/2491_zps1e38c13e.jpg.html)

Finally got to lift the car today & discovered that my right front caliper has the pads pinned against the rotor hard enough that the wheel won't spin under it's own inertia. Going out now to check the other side. looks like new caliper time. While I'm at it, might as well replace the master, too. Should the booster be replaced at the same time? Also getting new rotors due to warping, so will replace wheel bearings while I'm at it..

Side question: Does anybody sell brake line kits for these cars, or would I have to get / make custom bent lines if I wanted to replace them?

Longest "simple brake pad job" ever, lol!

Ben

drewsdeville
04-16-13, 08:17 PM
If the booster holds vacuum, it's fine. You'll want to bend/flare your own lines. Even if pre-bent are available, which is unlikely for this car, they'll be a hefty chunk of change. Brake line stock is under $1 per Ft, flare nuts and unions are cheap, and the parts counter will loan you the bender and flare tool if you need. If the calipers are seized, replace the wheel cylinders as well while the system is open.

The Ape Man
04-16-13, 08:21 PM
Unless the piston was slightly cocked that tool should have done the job. this assumes the top was popped off the master cylinder : )

Sounds like the caliper is sticking. There should be LOTS of heat after a drive.

jayoldschool
04-16-13, 08:49 PM
As Ape has mentioned, top must be off the master when compressing piston. I think your master is fine. Those tools are tough to use, I really suggest a big C clamp. It is possible that you didn't compress the caliper enough. Or, the piston is seized. Easy enough to figure out once the caliper is off. No need to replace rotors and bearings. Just get the rotors turned, and repack bearings. Yours are probably nice US made, where your replacements will be Chinese. Pads are likely glazed.

Benzilla
04-16-13, 09:14 PM
The top was off the master cylinder while compressing the pistons. ;) Pistons were compressed all the way in. Rotors spun freely after initial pad installation. It was sometime after completing the installation that the piston(s) compressed & got stuck that way.

I was really planning on doing the master cylinder, only because I've never touched it, and I'd hate to do all this work & have it go out a couple months down the road, requiring a third brake bleeding. I'm getting into the "fix it before it breaks so I don't have to tear into it again" mode. Plus I thought it would rule out the possibility of bad pedal feel caused by a tired unit.

Is there a place you'd recommend for turning rotors? I know the left one is slightly warped & I wondered about passing the minimum thickness for my rotor. The manual says they start at 1.037" thick, and I don't know if they've been turned already by a previous owner. I was under the impression that it was better to replace wheel bearings entirely than just repacking them when working on a very old car. Was I wrong?

Thanks again,
-Ben

jayoldschool
04-16-13, 09:59 PM
I never replace bearings. I repack. I'm 40. I still have a car I got when I was 15. I'm oldschool for a reason... lol

Any parts store can turn rotors.

It may not be the piston on the caliper that is sticking, it may be the guide pins. Go with new o rings and guide pins, lubed appropriately, when you put everything back together.

Personally, I see no reason to replace a master if it is not bad.

Benzilla
04-16-13, 10:06 PM
Thanks, all good to know! I carefully coated the guide pins with brake grease before installing & torquing, so I'd be honestly surprised if they were causing the problem.

How many times can one turn a rotor before it's garbage?

Sounds like the order of the day is just new calipers & a rotor turning then. ( ahh yes, and rear wheel cylinders while I'm already introducing air into the system again, I guess.)

Ranger
04-16-13, 10:25 PM
I know I'm gonna get beat up, but I'll go out on a limb here and say it's the ceramics. I recall a buddy of mine put a set on his car a few years ago and had the same complaint. Took them off and put on semi metalics and all was well. :hide:

Benzilla
04-16-13, 10:42 PM
I know I'm gonna get beat up, but I'll go out on a limb here and say it's the ceramics. I recall a buddy of mine put a set on his car a few years ago and had the same complaint. Took them off and put on semi metalics and all was well. :hide:

I initially wondered about the ceramics causing problems, but we were able to deduce that the cause of (at least part of) my problem was seized calipers overheating the crap out of the front brakes. :)

MrHolland
04-16-13, 11:22 PM
I too wouldn't replace the master cylinder or the steel lines unless something was wrong with them. I would however replace the rubber hoses. Brake hoses can/will deteriorate from the inside. The outside can look operational while the inside can be deteriorated to the point of not letting brake fluid flow freely. Many times this can be the initial cause of failing calipers. Once the caliper is exposed to higher than normal levels of heat it will be ruined. JMHO though, and nothing more. Good luck!!!

The Ape Man
04-17-13, 08:57 AM
Personally, I see no reason to replace a master if it is not bad.

I just replaced my 33 year old one. Tried not to....

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If you know how to bench bleed the master the system does not need another bleeding.

I know it sounds impossible but it's twue.

deVille33
04-17-13, 04:25 PM
I have successfully freed sticky caliper pistons by forcing the pistons in and out a few times. The boots keep the pistons from rusting. Sometimes the fluid in the bottom of the piston recess will have residue in it. It residue is from the brake fluid working on the various metals and the rubber in the system. Use denatured alcohol as a medium for cleaning. It will not cause the rubber to deteriorate.

drewsdeville
04-17-13, 06:22 PM
I have successfully freed sticky caliper pistons by forcing the pistons in and out a few times. The boots keep the pistons from rusting.
The boots keep them from rusting from the elements, but most of the time rusted piston and caliper bores are caused by the absorbtion of water into the brake fluid. Brake fluid is hydroscopic, and absorbs ANY type of moisture it comes in contact with - and that includes humidty in the air. This is also what causes the dark/milky/opaque brake fluid the OP noticed.

That said, I wouldn't recommend "fixing" the calipers by running the pistons in and out a few times. Calipers are cheap to replace. If you really feel the need to repair them, push the piston out, remove the seal, be sure the bore is re-useable, install new seal and piston, and reassemble...

If there is a lesson to be learned here, it's to change your brake fluid on a semi-regular schedule - else risk interior corrosion of the brake system.

deVille33
04-18-13, 11:45 AM
[QUOTE=drewsdeville;3288359]The boots keep them from rusting from the elements, but most of the time rusted piston and caliper bores are caused by the absorbtion of water into the brake fluid. Brake fluid is hydroscopic, and absorbs ANY type of moisture it comes in contact with - and that includes humidty in the air. This is also what causes the dark/milky/opaque brake fluid the OP noticed.

I realize this, but as he has replaced the flex hoses already, I assume that the caliper has been flushed of moisture contaminated fluid. Your statement that calipers are cheap to replace is suspect to me, as you are most likely referring to the inexpensive rebuild units available from AutoZone and others. When it comes to braking systems, I prefer to replace with new units from EIS or remans from Cardone.

drewsdeville
04-18-13, 02:16 PM
I realize this, but as he has replaced the flex hoses already, I assume that the caliper has been flushed of moisture contaminated fluid. Your statement that calipers are cheap to replace is suspect to me, as you are most likely referring to the inexpensive rebuild units available from AutoZone and others. When it comes to braking systems, I prefer to replace with new units from EIS or remans from Cardone. Well, he did mention that the fluid is currently dark and muddy...so I wouldn't assume it's been flushed. But even if the fluid was replaced recently, that doesn't negate the effects of the likely waterlogged fluid that was in there for years before... If the caliper was rusted before the new hoses and fluid, it was still rusted afterwards as well. The damage was already done. Generally, it's not until the pistons are compressed that the calipers seize, which is why we didn't see the results until a pad change - And yes, I was referring to remain Cardone units. They are relatively cheap, in my opinion...but perhaps everyone views the word differently.

Benzilla
04-20-13, 12:38 AM
Paragraph 3 of my original post states that the fluid was bled right after changing the pads. Also see paragraph 3 of post #19 :)

It's going to the local AC Delco shop on Monday. I'm trying out a new place. I need a shop I can trust if I need one. I do most of my own work, but both cars end up at a shop once a year or so... Figured this would be a good test for them.

I'd assume AC Delco would make a fine replacement for calipers. You can get them on Rock auto reasonably. Turning rotors & replacing wheel cylinders as well.

Ben

77CDV
04-20-13, 11:59 PM
Good luck, Ben. Hope this shop comes through for you. :)

Benzilla
04-23-13, 04:36 PM
Got it back today, seems they did a good job. On the way home someone tried to pull out in front of me & I had to make an emergency stop. Brakes felt great, actually locked them up & swung the back out a bit. I've gotta remember I don't have ABS in this one, got too used to driving the '90 Brougham!

Is it normal for there to be a bit of pad to rotor contact at all times? Or is there supposed to be enough space that there's no contact until you hit the pedal?

http://i24.photobucket.com/albums/c40/Cadillac_guy/null_zpsdb2d460e.jpg (http://s24.photobucket.com/user/Cadillac_guy/media/null_zpsdb2d460e.jpg.html)
http://i24.photobucket.com/albums/c40/Cadillac_guy/null_zps4ea0cd0d.jpg (http://s24.photobucket.com/user/Cadillac_guy/media/null_zps4ea0cd0d.jpg.html)
http://i24.photobucket.com/albums/c40/Cadillac_guy/da289515-4e65-4480-b0dd-fe02c1e2c115_zpsb0ad78ff.jpg (http://s24.photobucket.com/user/Cadillac_guy/media/da289515-4e65-4480-b0dd-fe02c1e2c115_zpsb0ad78ff.jpg.html)

turbojimmy
04-23-13, 04:49 PM
There's contact at all times.

What was the issue? It sounded to me like your back brakes weren't working properly and over-taxing the front.

Benzilla
04-23-13, 05:50 PM
When I replaced the front pads, bled the lines & replaced the flex hoses; it overtaxed the calipers & after a bit of driving, they both froze up & pinned the pads against the rotors, effectively overheating them to the point of almost complete inoperation. So, new front calipers. While I was at it, I had the rotors turned & bearings repacked, and new rear wheel cylinders installed. Just for preventative maintenance. rear pads still have plenty of life on them.

EDIT: Does anybody know if the calipers & drums were painted from the factory, or if they were always just raw metal? After seeing how the old ones looked, I was thinking about trying to protect them somehow. I just hate rusty metal... There was a guy on CarDomain who painted his drums GM corporate blue, it looked a bit odd, but GM did paint a lot of seemingly random parts in that color.

jayoldschool
04-23-13, 06:48 PM
They were raw metal. On my cars, I use high temp paint on them. Flat black for rear drums, and "Cast Blast" natural finish on the rotor hats and vanes.