02 Rx300 Brakes Lack 'braking Power'

[Rx300_coach]

Hi, this is actually my fathers account but i just wanted to ask a quick question.

I drive the Rx300 occasionally as i own my own 2002 Honda Civic..two very different cars i know, However when i am driving the speedlimit in the Lexus i find braking distance is insanely large. i mean sometimes i find myself literally pushing the brake to the floor in order to get the vehicle to come to a complete stop in time. Are all Rx300s like this? I highly doubt our brakes are gone since our car has a mere 35 000km on it.

Also i am accustomed to driving an extremely light commuter car so this may be the difference i'm seeing. However, i feel that the Lexus should have possibly bigger brakes with more stopping power.

[TunedRX300]

You needs to replace your brake fluid every two years. Brake fluid attract water over time and lower its boiling point. When it boils you have air in RX's calipers and brake lines. Air is compressable and reduces braking effectiveness.

I agree that RX's stock pads and rotor sizes are small compare to its weight. Just because SUV is not a sporty car there is no reason to design a weak braking system. When one needs to stop avoid an accident, bigger brake rotors, multiple pistons, and bigger brake pads save lives - does not matter what kind of car it is.

[Rx300_coach]

Thank you for replying,

I will bring this to my father's attention next time he's in at lexus. he doesn't seem to care about the braking power but i definately don't like the idea of the brakes being so soft.

Perhaps will even look into an aftermarket brake kit as well.

Thanks again for letting me know i'm not the only one who thinks these brakes feel like they belong on my Huffy.

[wwest]

Hi, this is actually my fathers account but i just wanted to ask a quick question.

I drive the Rx300 occasionally as i own my own 2002 Honda Civic..two very different cars i know, However when i am driving the speedlimit in the Lexus i find braking distance is insanely large. i mean sometimes i find myself literally pushing the brake to the floor in order to get the vehicle to come to a complete stop in time.  Are all Rx300s like this? I highly doubt our brakes are gone since our car has a mere 35 000km on it.

Also i am accustomed to driving an extremely light commuter car so this may be the difference i'm seeing. However, i feel that the Lexus should have possibly bigger brakes with more stopping power.

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Here's the way to tell if your brakes are up to par...

At ~35MPH on a solid surface dry roadbed, after checking traffic behind, apply the brakes quickly and firmly, VERY firmly. With the advent of most modern vehicles being equipped with BA, Brake Assist, it is not unusual for the brake pedal to feel "soft" by design.

BA detects, monitors, the RATE at which you apply the brakes and actually BOOSTS the brake pressure beyond normal brake application independent, somewhat, of pedal pressure.

If the brakes are effective enough the ABS should activate to prevent lockup. Also the vehicle should stop in a straight ahead fashion, if any stearing input is required during severe braking then something is wrong.

And think about this. The brake system is designed to sustain brake fluid pressures beyond 3000PSI, if the brake fluid cannot get out with pressures at this level, how is it that humid air at atmospheric pressure, 14.7PSI, can get in.

IT CAN'T!!

I'm quite sure my 1992 LS400 still has the factory brake fluid after 14 years and 100k miles. My 78 Porsche, 98k miles, would also had I not upgraded to Boxster front calipers a few years ago.

And one more thing...

When I buy brake pads I ask for the most aggressive pad they have. I do not want long life brake pads, I want to live a long life. I don't care if the pads or so aggressive that they EAT rotors for lunch, pads and rotors are expendable/renewable, my life isn't.

[TunedRX300]

There are parts of the braking system that is not built to endure high pressure. For example, RX300's brake fluid reservior is made from plastic and its lid can be opened easily by design. Yet the brake fluid in the reservior is circulated in brake lines and calipers so water does get into the system.

Here is a quote from Stoptech's web site.

Brake FAQ

MYTH # 5 - BECAUSE THEY ARE NON-HYGROSCOPIC SILICONE BASED BRAKE FLUIDS ARE SUITABLE FOR USE IN HIGH PERFORMANCE CARS

DOT 3 AND DOT 4 brake fluids are ether based and are hygroscopic in nature - i.e. they absorb water vapor. As the braking system in not quite airtight, a significant amount of water can be absorbed from the atmosphere in the course of a year. A 3% water content in brake fluid drops the boiling point as much as 170 degrees F. Brake fluid should be completely replaced annually.

DOT 5 fluids are silicon based and are non-hygroscopic, which is good. They are also subject to frothing from high frequency vibration, which gives a soft pedal. Soft brake pedals may be OK in non-high performance cars (in fact, most drivers accept mushy brake pedals as normal) but they are not acceptable in any situation where the driver intends to modulate braking at high force values.

MYTH # 4 - BOILED BRAKE FLUID WILL BE SERVICABLE AFTER IT COOLS.

Once the brake fluid inside the caliper has boiled, it has lost a significant percentage of its original boiling point and should be replaced. It is not necessary to remove all of the fluid in the system, just bleed until clear fluid appears.

MYTH # 3 - A SOFT BRAKE PEDAL IS THE RESULT OF PAD FADE

The all too familiar mushy brake pedal is caused by overheated brake fluid, not overheated pads. Repeated heavy use of the brakes may lead to "brake fade". There are two distinct varieties of brake fade

A, When the temperature at the interface between the pad and the rotor exceeds the thermal capacity of the pad, the pad loses friction capability due largely to out gassing of the binding agents in the pad compound. The brake pedal remains firm and solid but the car will not stop. The first indication is a distinctive and unpleasant smell which should serve as a warning to back off.

B, When the fluid boils in the calipers air bubbles are formed. Since air is compressible, the brake pedal becomes soft and "mushy" and pedal travel increases. You can probably still stop the car by pumping the pedal but efficient modulation is gone. This is a gradual process with lots of warning.

[wwest]

"There are parts of the braking system that is not built to endure high pressure. "

Very true, I have no doubt that the plastic cap will fail long before the atmospheric pressure reaches even 100 PSI.

"its lid can be opened easily by design."

Why would you open the plastic cap of a perfectly functioning brake system?

"so water does get into the system."

Oh, I see, that's a good reason to remove the cap.

Stoptech's web site.

And you want us to swallow some salesman's marketing speil?

"As the braking system is not quite airtight, (Where, and in what way?) a significant amount of water can be ( "may be" would be much more appropriate wording) absorbed from the atmosphere in the course of a year. A 3% water (notice how SIGNIFICANT suddenly JUMPED to 3%..??) content in brake fluid drops the boiling point as much as 170 degrees F. Brake fluid should be completely replaced annually.

DOT 5 fluids are silicon based and are non-hygroscopic, which is good. They are also subject to frothing (frothing is a form of cavatation, formation of air bubbles in a liquid via separation of the molecular structure) from high frequency vibration (HIGH FREQUENCY VIBRATION, did somebody turn the woofer up really LOUD??) (hmmm, maybe from the brake squeal if the pads weren't chamferred properly...), which gives a soft pedal. Soft brake pedals may be OK in non-high performance cars (in fact, most drivers accept mushy brake pedals as normal) but they are not acceptable in any situation where the driver intends to modulate (you only need to "modulate" if you don't have ABS, as a matter of fact getting drivers to NOT modulate in ABS equipped vehicle has become a real problem!) braking at high force values.

MYTH # 4 - BOILED BRAKE FLUID WILL BE SERVICABLE AFTER IT COOLS.

Once the brake fluid inside the caliper has boiled, it has lost a significant percentage of its original boiling point and should be replaced. It is not necessary to remove all of the fluid in the system, just bleed until clear fluid appears.

And this statemet, above, is nothing but PURE BS.

"just bleed until clear fluid appears...."

Would all those who do not believe "dark" fluid would quickly recombine with "clear" fluid please just go ahead and leave the room?

And those who do not believe the gaseous molecules would recombine with the fluid formulation molecules can also leave.

Look, put a quart of water in a large sealed container and then heat the conatiner until nothing is left within but extremely high humidity air. Now let it cool, COMPLETELY, and what have you got left.

That original quart of water!

When we "boil" a fluid we break down the molecular structure, separating the gaseous molecules fomr the solids. Where do the gaseous molecules GO? The system is SEALED!

But more to the point, how does one KNOW when the brake fluid has boiled?

Was that brake fade coming down off the mountain pass due to frictional overheating of the pads or boiling brake fluid?

MYTH # 3 - A SOFT BRAKE PEDAL IS THE RESULT OF PAD FADE

The all too familiar mushy brake pedal is caused by overheated brake fluid, not overheated pads. Repeated heavy use of the brakes may lead to "brake fade". There are two distinct varieties of brake fade

A, When the temperature at the interface between the pad and the rotor exceeds the thermal capacity of the pad, the pad loses friction capability due largely to out gassing of the binding agents in the pad compound. The brake pedal remains firm and solid but the car will not stop. The first indication is a distinctive and unpleasant smell which should serve as a warning to back off.

B, When the fluid boils in the calipers air bubbles are formed. Since air is compressible, the brake pedal becomes soft and "mushy" and pedal travel increases. You can probably still stop the car by pumping the pedal but efficient modulation is gone. This is a gradual process with lots of warning.

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It is extremely, and I mean EXTREMELY, hard to bring your brake fluid in any modern day car to the boiling point, it simply doesn't happen.

After just three laps on the track at Pacific raceways I have seen the rotors on my 2001 C4 glowing cherry red and yet I am fully confident that the fluid do not reach its boiling point.

Now to be fair if I though the brake fluid needed to be changed out in any of my vehicles on a regular basis, or as the result of some severe or heavy duty, I would go out and buy the equipement and do the job myself.

I quite firmly believe that you will, in unduly flushing brake fluids, put yourself and yours in much greater danger via trusting some car dealers lowly paid gofer, McD graduate, to work on your brakes.

But, now, a little reality.

How many of us can remember transiting from non-boosted brakes to boosted brakes. MAN, did that pedal ever feel MUSHY! Anyone tried driving a non-boosted vehicle lately?

So now here we are again transiting to BA....

[Rx300_coach]

Very Informative posts wwest, i agree with you! it's probably the brake assist my son is feeling in the Lexus. As he's used to his base model civic which doesn't even sport ABS. And is a hellava lot lighter.

[TunedRX300]

I am not sure how a closed system with 100% liquid boiling into a mixture of gas and liquid can return to 100% liquid again. It is gas that can't escape and be turned back to liquid the problem.

DOT has requirement on brake fluid to spec both dry boiling point (fresh fluid) and wet boiling point (fluid with water). Why does DOT require to let consumers know about wet boiling point, if brake fluid never get a chance to attract water?

Here is another link that is provided by Yahoo.

Brake Fluid by YahooAuto

I respect that you have a strong opinion, but if you are so convicted that brake fluid never needed to be changed, please provide an URL from a reputable source. I am all ears to hear (actually read) about data and scientic reasoning.

[wwest]

"Question: What is "bleeding the brakes" and why is that sometimes necessary?

Answer: Bleeding the brakes is flushing the old brake fluid out of the master cylinder, brake lines, calipers and wheel cylinders and replacing it with fresh fluid.

Bleeding is necessary for two reasons:

1. To remove air bubbles that may have entered the system while repairs were being made, because of a leak or because the fluid level got too low. The air must be removed because it is compressible and can prevent a full, firm pedal."

There's your answer in a nutshell...

Repairs, leaks, or the fluid level getting so low air is SUCKED into the system by the mater cylinder.

2. To remove moisture contamination.

Now I ask you, if the only way air can get into the system is via repairs, leaks or extremely low fluid levels, how does water get in. Certainly not via the humidity of our atmosphere, AIR that is!

"Though the owner's manuals for most domestic vehicles have no specific time or mileage recommendations for replacing brake fluid,...."

Says a LOT if the new car dealers haven't been successful in getting the manufacturers to even "suggest" flushing and draining brake fluid on a scheduled basis.

".....recommending a change every two years for preventative maintenance is a good way to minimize the danger of fluid boil and internal corrosion in the brake system. At the very least, the fluid should always be replaced when the brakes are relined. "

NOT!

Again, the danger you expose you and yours to by relying on the dealer's routine maintainance GOFER, McD graduate, to mess around with your brakes on a regular basis far outweights any possibility of your brakes failing due to contaminated brake fluid.

[TunedRX300]

wwest,

I agree with your assessment on mechanics. Definitely DIY or find an experienced and trusted one to do all safety related works. But servicing brake flush is a different issue than claiming that it is not needed for the life of a car.

I saw you skipped the following portion on Yahoo Auto. Again, if you have a web link to explain that water can not be absorbed when brake is not serviced, please post.

2. To remove moisture contamination. Brake fluid needs to be replaced periodically because DOT 3 and 4 brake fluids are glycol-based and absorb moisture over time. This occurs whether a vehicle is driven 30,000 miles a year or just sits in a garage because fluid contamination is a function of time and humidity rather than mileage. Moisture enters the system past seals and through microscopic pores in hoses. It also enters every time the fluid reservoir is opened (a good reason not to do so unnecessarily).

After only a year of service, DOT 3 fluid may contain as much as 2% water. After 18 months, the level of contamination can be as high as 3%. And after several years of service, it's not unusual to find brake fluid that has soaked up as much as 7 to 8% water. Many vehicles that are six, seven or eight years old have never had the brake fluid changed!

As the fluid soaks up moisture, it thickens and becomes less able to withstand heat and corrosion. The result is a significant drop in the fluid's boiling temperature, which may under the right conditions allow the fluid to boil in the calipers. Once brake fluid turns to vapor, the bubbles cause an increase in the distance the pedal must travel to apply the brakes. This condition should not be confused with "brake fade" that occurs when the brake linings get too hot as a result of prolonged braking. Brake fade requires greater and greater pedal effort to stop the vehicle while fluid boil increases pedal travel and makes the pedal feel soft or mushy.

The danger of fluid boil is greatest in front-wheel drive cars because of the higher operating temperatures that are generated in today's downsized front brakes, and because the hydraulic system is split diagonally. Semi-metallic linings compound the heat problem by conducting heat from the rotors to the calipers. If the fluid contains a lot of moisture and can't take the heat, it'll probably boil.

DOT 3 brake fluid, which has long been used in most domestic cars and light trucks, has a minimum dry boiling point of 401 degrees F. A 3% level of water contamination will lower this by 25% or 100 degrees! DOT 4 "extra heavy-duty" brake fluid, which is used in many European cars, has a higher dry boiling point of 446 degrees F. DOT 4 soaks up moisture at a slower rate than DOT 3 but suffers a greater drop in heat resistance as moisture builds up. Only 2% moisture in DOT 4 fluid will lower its boiling point by almost 50% or 200 degrees

[wwest]

Since I thought I addressed "2" quite adequately I saw no sense in publishing it.............

[Dave_02RX300]

How often is it recommended to replace the brake fluid in an RX300? My Odyssey must have it done every 30k miles.

[TunedRX300]

Some Lexus dealer recommend a flush of brake fluid as part of 30K miles service. In Europe, I believe every car needs to pass brake fluid inspection every two years. To say that brake fluid last forever is wrong. There is no reputable source (DOT, SAE or automakers) makes that claim. Considering it only cost $10 to $20 per quartt, even with $60 of service cost, it is a safety measure that I would not skip.

[monarch]

How often is it recommended to replace the brake fluid in an RX300?  My Odyssey must have it done every 30k miles.

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The minimum recommended brake fluid replacement frequency interval is given in your Lexus Scheduled Maintenance Guide. Generally it's around 2-4 years or 30-60,000 miles. The factory fill brake fluid is genuine Toyota Brake Fluid http://i5.photobucket.com/albums/y189/mastertech/fluidss.jpg

available in 1 pint bottles from Toyota dealers for $3-4 a pint. A minimum of approx 4 pints are needed to replace the fluid in the system.

The label on the bottle of genuine Toyota Brake Fluid says: it's "a super heavy duty hi-temp brake fluid specifically designed by Toyota engineers to give superior performance in all Toyota Brake Systems where DOT 3 brake fluid is recommended." (all Lexus brake systems use DOT 3 fluid)