The Complete Brake Job

[The Critic]

Interesting articles. Here are a few excerpts:

Quote:
A research study published in the July 1997 issue of Brake & Front End magazine found that pad life was, on average, 62% shorter on a brake job where only the pad was replaced than on a brake job that included a caliper replacement.


Quote:
Visual evidence of caliper failure is present in only 1 or 2 out of 10 brake inspections, and, as a result, shops frequently have to explain why the pads they installed less than a year ago only lasted 15,000 miles.


Quote:
Heat and time dry out caliper seals and reduce the amount of pull-back as the seal ages. A new seal will pull back the piston about 0.015in. In comparison, an old seal may only be 0.010in or less. If the piston does not retract, it can cause the pads to drag.*


References:

http://www.ucx.com/documents/sellcalipers.pdf
*http://www.ucx.com/documents/preventmain.pdf

Perhaps that explains why my Saturn keeps going through rear brake pads at an alarming rate. The calipers pass a visual inspection, the pads are wearing okay, yet my pads are only lasting about 25,000 miles. The originals lasted 100k!

What do you guys think of replacing calipers as preventive maintenance? Would you agree that is necessary at every brake job? The second link provides some fairly convincing evidence on seal stretch, but their example is a bit questionable and seems to represent the exception to the rule. However, it seems to make sense to replace the calipers during a routine brake job if the vehicle has over 100k miles, as components are far more prone to failure due to age.

Discuss.

 

[tomcat27]

makes alot of sense after X years. not sure what "X" is tho...
it also makes sense to flush brake fluid, which few people do.

 

[1993_VG30E_GXE]

Calipers can last more than 16 yrs. Case by case basis I would think. My calipers are original OEM from 1993, but the brake lines need to be replaced.

Maybe inspect them and lube them OK if the piston is OK and the rubber boot thing that prevents the piston from rusting, is OK.

 

[Turk]

Interesting. I'll be replacing the rear brake shoes on my '01 Saturn SL1 tonight. Using grease & brakekleen. We'll see...

 

[1993_VG30E_GXE]

By the way Critic, I only mean that in a joking type of way - my previous e-mails. They aren't intended to be rude to you.

I'm stoned right now so I have no control.

 

[1993_VG30E_GXE]

tpitcher, I would check the slide pins too to make sure they aren't stuck. If you have rear disc brakes, I think the rear calipers usually fail before the front. A stuck pin can be removed with heat - you don't need to throw out the caliper.

 

[Shannow]

I can't understand why brakes have grown into a field where you now need to completely redo the entire system, where before, pads, a runout check, and a bleed would leave you good to go for another long time.

Why have the manufacturers made such a simple system (in it's pure form) so hideously planned obsolescent ?

 

[1993_VG30E_GXE]

Woops - you said rear shoes. Ignore what I said.

Brake lines are going to be a NIGHTMARE, especially when you buy raw line and bend it yourself like I'm going to do, to save the most money. I need to remove the whole front suspension on the Maxima, all the way down to the Transverse Link Gusset, just to remove the old lines out and new lines in.

I'll take photos. This is all within the next 2-3 weeks, as well I need to install the completed engine and my 2nd transmission (first one I will overhaul in the winter), AND replace the steering rack, replace rear brake calipers, replace those brake lines, replace 3 fuel pipes from gas tank (maybe have to lower the gas tank? Not sure) to engine bay, Buy gas tank adapter for transmission jack, un-freeze front caliper stuck pin....the car jobs NEVER END for me.

Paint the engine, clean the transmission bell housing, grind rust out of engine bay, paint it, use the MIG welder before winter to fix some rust damage.

OK I'm getting a headache now.

 

[1993_VG30E_GXE]

Oh ya, I forgot original poster, you should probably bleed the brakes too, get rid of the old fluid, clean the brake reservoir out. My ABS Pump failed on me after 16 yrs so I had to replace it with a JY part. I wonder if contaminated fluid cause it, the fluid was NEVER changed really. Brakes failed while I was in a parking lot and ABS light stayed on. All the fluid leaked onto the street.

 

[Familyguy]

I don't think I'd change calipers for "preventative maintenance." What I would do is to bleed and replace the brake fluid, make sure the caliper guides are lubed properly, and call it a day. I doubt there's anything wrong with the OP's calipers.

 

[labman]

Nothing last forever, especially if it is made out of rubber. Caliper seals and boots eventually get old and no longer do their job even if they look OK. Cleaning up the slides and other mechanical parts is an absolutely essential to every pad change. Depending on several things, it shouldn't be necessary to replace or rebuild the calipers every time.

One more time for the benefit of any new comers willing to measure the posts here against the real world.

In the common single piston caliper, the piston rides in a slightly over size bore, but only touches the seal, a square cross section ring that fits in a groove. When you apply the brake, the piston pushes the inner pad against the rotor, and the caliper slides in and pulls the outer one against the rotor. When you let off, the piston and caliper are pushed back just enough to clear by the wobble of the rotor. There are no springs. If the hardware is in good shape, the piston and caliper both move, but very little. If you do not lube and clean up or replace the hardware when you change pads, the caliper will not slide in as it needs to to pull the outside pad against the rotor. This is a frequent problem causing the inside pad to wear more and uneven braking.

As the pads wear, more and more of the piston stays outside the seal, untouched by the brake fluid. It is protected by a rubber boot, sealing out moisture, grit, salt, etc. Anything that makes it in past the boot can attack the the chrome plated steel piston. The plating is thinned where the it was abraded by the seal. It is slow, but rubber does abrade hard metals. Of course, the seal wears away too. The boot is next to the back side of the pad and heat from it and age harden the rubber and reduce its elasticity. It becomes less and less effective in keeping out yuck, even if it isn't cracked or torn.

Fresh fluid never touches the boot, the vulnerable part of the piston outside the seal, or the sealing surface of the seal. I doubt if flushing the caliper even disturbs the old fluid in the narrow annular space between the inner part of the piston and the bore. The inlet usually is near the bottom, but the outlet is always at the very top to bleed out the air. I am not even sure flushing the brakes carries any water or grit up and out of the caliper.

In time, the boot lets in enough to corrode the piston, both the plated steel ones and aluminum ones. Pushing the piston back with a lump of rust on it, either makes it stick, or the seal leak. Many times people will install new pads in calipers that were working fine, and then they either leak or stick. The solution is timely, preventative replacement of the old worn rubber parts and fresh lube on the piston. I prefer Sil-Glyde. A caliper kit is cheap, and rebuilding a caliper isn't that bad of a job. If you let it go too long, the piston is shot, and the cost of a piston and a kit is more than a rebuilt caliper. I have always rebuilt mine in time. After a rebuild or 2, all the original fluid is long gone before it can cause problems. One advantage of rebuilding my own calipers is that I know it goes back together with a good coat of Sil-Glyde on everything, especially the bleed screw, not brake fluid or the special brake greases that are just as hygroscopic.

Cleaning up the caliper and hardware, replacing the old, worn rubber parts, and lubing everything good prevents common problems like sticking or leaking calipers, uneven pad wear, uneven application, and broken bleed screws.

After 5 -10 years, it is good to replace the rubber brake hoses. Master cylinders are up away from the heat, salt, moisture, and grit, and seem to last much longer. If you have salt, it is good to inspect the steel brake lines paying particular attention to places where crud collects, holding moisture and salt against them. Badly pitted ones should be replaced.

In the 3 years I worked in a brake shop, leaking, sticking calipers, uneven wear, broken bleed screws, bad hoses, and brake lines rusted from the outside happened every day. We specialized in trucks. I never remember problems with brake fluid boiling. I never heard of replacing the fluid either.

 

[Kruse]

I'm all for having a safe and working brake system, especially since I have a wife and three kids who depend on the safety of my work.

However, has anybody considered that this magazine exists to sell parts and that perhaps there is alterior motive here? Once again, if a part needs replacing, I'm all for it.

 

[Familyguy]

Originally Posted By: labman

In the 3 years I worked in a brake shop, leaking, sticking calipers, uneven wear, broken bleed screws, bad hoses, and brake lines rusted from the outside happened every day. We specialized in trucks. I never remember problems with brake fluid boiling. I never heard of replacing the fluid either.


You worked in a brake shop for 3 years and have never heard of replacing the brake fluid? Ummm.....

Call me crazy, but I bleed and replace my brake system every 2-3 years.

 

[LotusLover]

Nice, complete post, Labman.



I too notice the seeming increase in failure of calipers on REAR disc brakes. IMO factors may include:


Increased use of road salt by authorities, especially liquid ice melters, which seems to get into EVERYTHING. Much more than granuated....

The open style of wheels nowadays. The full wheel covers on my '58 Impala never seemed to let that much water or salt in.

Or maybe it was the spinners?

Seriously,
My strategy is to peel back the piston to caliper boot (seal) just a little and inject a little bit of silicone spray. My hope is that this will coat the areas of the bore where brake fluid never reaches. The silicone will not deteriorate the rubber.

I also coat the outer surface of the caliper piston seals with SYNTHETIC brake grease to resist moisture, just a thin coat. Again, the synthetic will not affect the rubber. The pad will prevent the grease from wicking onto the rotor. (Not that the synthetic grease ever "wicks", anyway.)


And of course, any sliding surfaces and guide pins must be free of corrosion. The pads should always fall out of the guides. Sometimes the cast caliper rusts under the stainless steel, which tightens and binds the pads over time. (Going back to my initial points.)

PS So, why do folks complain about Brake Wobble when it performs a vital service????

 

[tomcat27]

ya ever notice how brake fluid that starts out almost clear eventually takes on a caramel hue? that's moisture in the fluid. Brake fluid is alcohol-based, and alcohol absorbs water. that moisture in the fluid corrodes metal brake parts, including pistons and ABS parts. that's why periodic fluid changes are recommended.... something that past generations never thought of. of course, past generations were ok with replacing plugs and points every year.

 

[buster]

Good info folks. Time to replace the calipers on the Honda. I went thru this last set of pads very quickly. Rotors too.

 

[Vikas]

Come on, just read the name of that document, it is called "sellcalipers.pdf". That should give you hint as to why that document was published.

Besides, if you caliper is hanging even a little bit, you should be able to figure it out quite easily. If you have a manual car, make sure that it rolls freely in neutral or with the clutch in. If you are good, you are already doing this subconsciously and will *know* if a caliper is hanging. A better way is to aware of one wheel being significantly warmer than others or worse, typical brake smell.

Guys who are on this forum should know if the cars they are driving day in and day out needs the calipers replaced. They certainly should not be fall in to "upsell" trap.

- Vikas

 

[johnd]

I'm not sure I have experienced 62% more wear but experience has taught me that pads do last longer if you do rebuild the calipers when you replace them. I change out fluid every two years regardless. I have had mechanics tell me that used to be, one never replaced brake hoses but that failures now are much more common (typically internal collapse causing brakes to not want to release). Nobody seems to know the reason for this-could it be that in a disk brake car, the pressures are a lot higher than they were for drum brakes?

 

[labman]

More brake hoses may be failing because more old cars are still on the road. As a kid in the 50's I hardly remember any pre WWII cars on the road and very few 40's. I remember how old my uncle's 53 Plymouth was before he finally replaced it with a 62. I can only remember one brake hose failing before it was 10 years old, and yes, a failure to release. I still have the originals on my 02 cavalier, but have replaced the ones on my 77 truck, disks, twice.

 

[benjamming]

OEM rear pads lasted 55k miles on our '02 Accord. Replacement pads lasted until 125k miles. Wear was less than 1 mm variation between OEM pads & replacement pads. What was that again about caliper replacement? Amazingly crazy!