OT-Car brakes

[Chuck Wintle]

Decided to change the front brake pads on my sons 1997 Honda Civic on the weekend. The pads were worn out so the new ones were installed. Noticed afterwards the brake pedal was still low and a bit spongy and definitely not what it should be. Would that indicate a bad master cylinder or should the brake system just need to be bled of air? We never touched the calpiers except to push the pistons in to clear the new pads. :D

[Mitchell Andrus]

Take the rotors out for cutting/replacement. If in doubt, go get the brakes rebuilt by a pro shop.

Having to explain to a jury that you thought the brakes would work following a driveway overhaul is as scary a thought as brake failure itself.

[Jim O'Dell]

I'd bleed the brakes personally. If they were really thin, then the master cylinder reservoir could have run dry, and gotten air in the lines, I always bleed the lines when I install pads. Many of the pro shops don't, but will sell you a brake flush!! If bleeding the brakes doesn't improve the pedal feel, then you could need a master cylinder. If it has ABS brakes, there could be a problem there. If so, definately find a Honda specialist for that (not all of them still work at a dealership) Jim.

[Chuck Wintle]

Jim,
Thanks. The car is going to the garage this afternoon. I don't really have the time or tools to blled the system and with a spongy pedal it could be the master cylinder that has gone bad. Its beyond my capacity now. :)

[Craig Che]

Bleeding the brakes only requires a little wrench to open the bleed valve and someone to push the pedal down when you open it.

[Matt Meiser]

Yep. Have the helper pump the pedal several times then hold it down while you crack the bleed screw open and bleed out the air. The bleeders just make it easier to do alone.

Matt, who was the helper many, many times growing up.

[Kyle Kraft]

I have an '03 Odyssey, and the manual says to change the brake fluid annually. First I thought this was a crock, but when I changed the pads on all 4 wheels and had a peek inside the master cylinder, I realized why they tell you this. My Odyssey has a master cylinder with a vent hole in the cap. The domestic vehicles I have owned have a vent hole in the cap but also have a rubber membrane that prevents ambient air from ever touching the fluid....the Odyssey doesn't. This small difference means on the Honda, condensation has the opportunity to form inside the master cylinder reservoir thus necessitating the fluid change. Kind of a messy pain in the rear, but I accomplished it without any problems.

Bottom line is if your manual says to change the brake fluid, it may not be a simple ploy to add to the dealers bottom line.

[Mike Henderson]

I have an '03 Odyssey, and the manual says to change the brake fluid annually. First I thought this was a crock, but when I changed the pads on all 4 wheels and had a peek inside the master cylinder, I realized why they tell you this. My Odyssey has a master cylinder with a vent hole in the cap. The domestic vehicles I have owned have a vent hole in the cap but also have a rubber membrane that prevents ambient air from ever touching the fluid....the Odyssey doesn't. This small difference means on the Honda, condensation has the opportunity to form inside the master cylinder reservoir thus necessitating the fluid change. Kind of a messy pain in the rear, but I accomplished it without any problems.

Bottom line is if your manual says to change the brake fluid, it may not be a simple ploy to add to the dealers bottom line.
Having to change the brake fluid annually sounds like poor design or excessive caution. Every car I've owned has had a breather hole in the master cylinder reservoir (it has to have a breather because the fluid level falls as the pads wear) and the fluid is in cotact with the air. All of those cars recommend changing the brake fluid at fairly long intervals, such as 50K miles. The only serious contamination I've ever heard about in brake fluid is moisture and that's because the moisture causes rust in the wheel cylinders. Under extreme conditions (racing) the moisture can boil, but under normal usage, as in a family car, that's unlikely.

But maybe I'm missing something.

Mike

[K. L. McReynolds]

Over time, the vent hole in the MC cap will let in moisture from humidity. Changing brake fluid has been recommended by vehicle manufacturers for years, it is just buried in the manuals.

The spongy pedal after pushing the caliper pistons back into the calipers is not unusual. A better way is to open the bleeder screw, push the pistons back, closing the bleeder just before the pistons stop. That eliminates the spongy pedal and requires new fluid---especially when each caliper is bled once after replacing the pads.

The other reason for a different feel to the brake pedal when the rotors are not surfaced/replaced is the fact the old rotors are smooth from use, and new pads often glaze easily in that situation. Rotors can also be warped slightly. Those two conditions together will result in a low spongy pedal.

[Mike Henderson]

Over time, the vent hole in the MC cap will let in moisture from humidity. Changing brake fluid has been recommended by vehicle manufacturers for years, it is just buried in the manuals.

The spongy pedal after pushing the caliper pistons back into the calipers is not unusual. A better way is to open the bleeder screw, push the pistons back, closing the bleeder just before the pistons stop. That eliminates the spongy pedal and requires new fluid---especially when each caliper is bled once after replacing the pads.

The other reason for a different feel to the brake pedal when the rotors are not surfaced/replaced is the fact the old rotors are smooth from use, and new pads often glaze easily in that situation. Rotors can also be warped slightly. Those two conditions together will result in a low spongy pedal.
I agree with McReynolds. If air in the lines is not the problem it's due to the pads not bedding well to the rotors. What I do when the pads don't bed well after changing them is to take the car to a safe place and make a few panic stops. That usually beds the pads and gets rid of the spongy feeling. The pedal should feel better after about two stops, and it usually doesn't take more than four to bed them firmly.

Mike

[Ken Fitzgerald]

First, if you aren't fairly handy with mechanicing, I'd recommend taking brake problems to an experienced mechanic. As stated earlier....it's too late after your vehicle doesn't stop.

I bought an '83 full sized Blazer that I eventually got rid of because of transmission failures. It also had a number of brake problems, until it went off warrantee and I took over the job of maintaining the brakes.

I live in a mountaineous area. My wife wears out brakes more often than I. She's actually driven home with a package on the rear bumper and it was still there 2 miles later when she arrived home.....Get the picture?

Dot 3 and Dot 4 brake fluids are ethelene glycol based brake fluids. As such they will absorb moisture over time. As your brake pads or shoes wear the level of the brake fluid in the master cylinder will drop as more fluid is in the caliper to make up for the decreased pad thickness. When these fluids absorb moisture, it significantly lowers their boiling temperature which can be a real problem when you are using the brakes alot. Your brake systems gets hot....the fluid boils and the brakes fail.

Dot 5 brake fluid is silicone based. It will not absorb moisture BUT...moisture will get into the system. Clumps of pure water can occur and end up being collected in the calipers....Water boils at ....212?...Same result ...brake failures due to water in system.

Remember, I drive a lot in the mountains. I change the brake fluid in my vehicles every 3-4 years and earlier if I notice the color/purity of the fluid changing. Changing it myself (I'm not a mechanic but I'm mechanically inclined) isn't that difficult and I don't worry about brake failures when I'm descending a mountain in my 1990 F-350 4WD towing my 9000+ lb. 5th wheel trailer.

Might be over kill, but I also turn the rotors every time I replace the pads. Flat surface against a flat surface. Overkill...maybe...but I leave my driveway and within 1 mile descend an 11% 800 foot elevation drop grade to get to the rest of town.....

As a result I change rotors on my truck....once...in 127,000 miles....maybe more often than someone else would.

Maybe change rotors (due to the extra turning) 1 or 2 times in the life of our old Toyota 4-Runner and our new Honda Accord.....Cheap insurance in my book.

That '83 Blazer......The Lewiston Grade ...US95......6 mile...3,000 ft drop....3 miles of 6% grade.....3 miles of 7% grade.....9 truckers killed at the bottom of the hill in the 25 years we've lived here......The brakes on that Blazer gave out twice on that hill with my wife and kids in the car....once I was driving...once Sharon was driving....It didn't happen again once I took over the brake maintenance on that vehicle.....

YMMV...........

[Greg Peterson]

Early 90's Ford F series a problem with brakes overheating. The solution was to replace the steel caliper piston with a phenolic piston. The phenolic piston did not transfer heat as efficiently.

The braking system on a vehicle is little more than an energy transfer system. Energy can not be destroy, merely transferred.

Mechanical energy created by the engine is converted into forward inertia. When you apply the brakes, forward inertia is converted into heat.

Drive your rig around the block, using your brakes moderately. Park the vehicle and lightly touch the rotor. You will see that the rotor is warm or very warm.

Heat is the number one enemy of brakes. And they get a lot hotter than you imagine.

[Ken Fitzgerald]

Greg....My F-350......460 cu. in...5-speed manual.....4:10 ratio.....I use the gears too for braking when towing.....but.....my wife won't drive it....She's afraid she'll get stopped at a stop light on a hill and never get the truck moving again because it's manual transmission.:rolleyes:

[Chuck Wintle]

Thanks to everyone for the advice. The car is at the mechanics and all that is needed is for me to pay the bill.:eek:

[Tim Wagner]

Well it's good your getting it fixed, however, in the future if anyone runs into this problem another item to check would be the caliper slide pins themselves. there are two on each one, and often 1 of them will freeze and stop moving. this will cause the caliper to not apply even pressure on the pads when applying the brake, causing a soft and spongy pedal.

Brake fluid does need to be changed yearly or at the very least bi-yearly. brake fluid is designed to absorb moisture and clean the system of dirt. changing the fluid periodically helps reduce corrosion and helps keep calipers and wheel cylinders, master, moving and working freely.

if your car is equipped with ABS, then please open the bleeder when compressing the caliper pistons. it's not a good idea to push old fluid back thru the ABS unit.

[Randy Denby]

One other good reason ,I've yet to see mentioned, for changing brake fluid periodically is this.....the moisture and resulting rust/trash will destroy an ABS system . And they can be very costly. My mothers Chevy truck was 1800.00 for the ABS alone.

[James Rambo]

The reason the book calls for the brake fluid to be replace every years, falls into the same rule as for the oil in the engine. The fluid brakes down due to heat and pressurizing with every stop you make. How often do you change the oil in your cars engine. With average use today, we drive about 15,000 miles a year that means 5 oil changes a year. Your car is 10 years old that is a lot of stops on the same brake fluid.

[Mike Henderson]

The reason the book calls for the brake fluid to be replace every years, falls into the same rule as for the oil in the engine. The fluid brakes down due to heat and pressurizing with every stop you make. How often do you change the oil in your cars engine. With average use today, we drive about 15,000 miles a year that means 5 oil changes a year. Your car is 10 years old that is a lot of stops on the same brake fluid.
Perhaps a better comparison for the brake fluid would be how often manufacturers recommend changing the transmission fluid, rather than the engine oil. The reason is that the engine oil is contaminated by the blow-by from the engine cylinders while the transmission oil only breaks down from heat and is contaminated by swarf from wear of the transmission components. The environment of the brake fluid has more in common with the environment of the transmission fluid than the engine oil.

Additionally, brake fluid "wears out" from the accumulation of moisture and not from being heated. So the recommended period for changing it would be how rapidly it accumulates moisture and swarf. While everyone should do the amount of maintenance they feel comfortable with, my opinion is that annual changing of brake fluid is excessive, unless the conditions are extreme - or unless the manufacturer recommends annual changes.

Mike

PS - while this is off topic, I don't know any automobile manufacturer who recommends changing the engine oil every 3K miles. One car I own recommends oil changes every 12K miles (with synthetic oil), and the other recommends oil changes every 7.5K miles. Engine oils are so good today that even people who neglect maintenance get way beyond 100K miles of service without wear issues related to engine oil (crankshaft main journals wearing, cylinder walls/rings wearing, even valve guides leaking oil). I've taken apart engines with over 100K miles (and without excellent maintenance) and there's almost no ridge at the top of the cylinder and you can't measure the wear on the crank journals. More engines fail because of oil leaks (and running the engine without oil) than fail because the engine oil breaks down and quits lubricating.

[Russ Filtz]

DO NOT let them change the rotors out unless they were totally scored or you had bad pulsations when braking in addition to the spongy feel. It's not needed, just a waste of money. Hardly anyone turns rotors anymore, just replace them if needed.

My bet is on air in the line. A simple bleed, or fluid replacement should be all that's needed. I use Russell Speed Bleeders (no affiliation!) and ATe brake fluid. The brake fluid comes in metal cans (plastic CAN let moisture through given time) and in two colors, blue/amber. When you do flush the fluid, you change colors each time and it's obvious when you get the old stuff out. ATe is German made and OEM for the likes of BMW, etc.

The speed bleeders replace the stock bolt for bleeding and incorporate a spring loaded BB that acts as a check valve. Lets fluid out when you press the brake and automatically springs closed when you let off. Foolproof as long as you remember to keep filling the reservoir as you bleed! Easy one-man bleeding.

[Russ Filtz]

Additionally, brake fluid "wears out" from the accumulation of moisture and not from being heated.

Mike, I don't think this is entirely the case. Oil does "wear" out faster by getting dirty from blow-by, but I don't think the moisture should do much, unless you only drive the car short distances and never get it warmed properly (which should then boil off any moisture). With always cool oil you might start getting condensation and rusting in any ferrous in the engine (which then could cause more contamination).

Also, not sure on the synthetics, but petroleum based oils can degenerate. Oil is a conglomeration of molecules, not all the same. Some have stronger bonds, stay in longer chains, etc. In the old days (and maybe even now) they used to market "racing" oil and what no-one realized was that it was old recycled oil.

Basically any long-chain oil molecules that made it through a stint in the engine and didn't break down had superior internal bonds. By filtering all the crud and short-chain molecules out, you're left with oil that can take a beating. Of course you can charge more for "racing" oil than you can for "recycled". Not an industry insider, so that whole story could be a marketing gimmick too!

[Cliff Rohrabacher]

Noticed afterwards the brake pedal was still low and a bit spongy and definitely not what it should be.

You may have got some air in the system bleed it and see.

I recommend that you completely replace all the fluid at least once every couple of years. It gets dirty entrains water vapor and needs to be removed and replaced. The easiest way to do this is with a vacuum pump. However with a foot or less of poly tubing dumping the fluid into cans at each wheel ( VIA the bleeder valve left open, a slave stepping on the brake pedal continuously and another slave feeding fluid into the reservoir you can do it yourself and spill not one drop. Pump fluid through till it runs clear and clean. Then just bleed each cylinder and you are golden.

Rebuilding the calipers is also very easy. Unless you let old polluted fluid remain in the system and got corrosion in the cylinders you would only need to replace the O-rings and seals and maybe - but not bloody likely - the pistons.






Would that indicate a bad master cylinder or should the brake system just need to be bled of air?

I think not. The master shouldn't just fail right after you re assembled the system but it's a Honda so I can't say. No that wasn't sarcasm I really can't say.


I always crack the bleeder valve when I push a piston in a caliper back - always as in every single time~!! This means I usually have to bleed air. Not always though.
I don't like the notion of reversing the forces in the master and maybe pushing loose corrosion particles back through the system.

[Greg Peterson]

Ken- Have you upgraded the brakes on your F350? Cross drilled rotors do an excellent job of dissipating heat and ceramic pads hang in there a lot longer. The combination of the two should give you superior braking performance.

I saw comedian lament that he didn't need a car that went from 0-60 in 4.5 seconds. He needed a car that could go from 85-60 in .5 seconds. :D

[Ken Fitzgerald]

Greg....The last time I reworked the brakes, I considered everything you mentioned. At the time my daughter worked for a large after-market autotive parts company and I could get parts at an extremely reasonable price. If I have to redo the brakes again on this one I will probably do that. However, at my age, I'm not sure how much longer I'll be towing this 5th wheel. Regardless, I'll be buying a new pickup in the next couple of years when I retire.

[Joe Pelonio]

Mike

PS - while this is off topic, I don't know any automobile manufacturer who recommends changing the engine oil every 3K miles. One car I own recommends oil changes every 12K miles (with synthetic oil), and the other recommends oil changes every 7.5K miles.

My '07 Ford Ranger manual shows every 3,000 miles. It also shows every 7,500 but only for cars that are driven on the freeway every day in light traffic with no dust in the air. Basically they have declared that almost all of us need to be on the hard duty 3,000 mile schedule because we drive in heavy stop and go traffic and make a lot of short trips. Every dealer, Ford, Jeep, and also independent shops that I have gone to have always put 3 months/3k miles on the "next service due sticker" including the one I got last week from Ford.

Mind you, I compromise, since I think my trucks's "duty" is in between and go 4,000-4,500 between changes.

[Randal Stevenson]

You did remember to pump the brakes once the pads and calipers were mounted to reset them, to the rotor (spelled router, can you tell where my mind is?)?

You would find out if you hadn't, the first time you stopped otherwise. Simple I know, but I've seen it done before.