Break pads & disks replacement - 2002 Avalon XLS

Over the years, I've replaced lots-o-brakes on various cars with disks. However, the Avalon is the fist car I've ever had with ABS breaks. Is there more involved with these ABS brakes than regular disk breaks when it comes time to replace the pads and disks, or should I just dive right in? I'm just used to taking the top pin out of the calipers and swinging them down to reaplace the pads, etc.

Thanks, Steve

Reply to
Steve Henderson
Loading thread data ...

It's BRAKES, not breaks.

No, the ABS should not change the method of replacing pads or rotors. ABS can play a role in bleeding the brakes, but yous hsould be able to replace pads and rotors without getting into the brake bleeding procedure.

Reply to
Jeff Strickland

Jeff Strickland wrote: It's BRAKES, not breaks.

No, the ABS should not change the method of replacing pads or rotors. ABS can play a role in bleeding the brakes, but yous hsould be able to replace pads and rotors without getting into the brake bleeding procedure.

Thanks, Steve

Reply to
Steve Henderson

ABS does not have any role in bleeding the brake lines in an Avalon or any other Toyota sold in the U.S. I have never seen a vehicle where the procedure for bleeding brake lines was different in a vehicle with ABS.

Reply to
Ray O

I suspect you are right, but if there was any issue with brakes that involved the ABS, it would be in bleeding the system, not in replacing pads or rotors. I didn't want to say that ABS presented no new considerations because I just can't be sure that a statement to that effect would be accurate. It is better to suggest that the ABS might come into play in bleeding than to suggest that ABS could be completely ignored.

Reply to
Jeff Strickland

I know I am right. (don't tell my wife, she automatically assumes that what I say in incorrect)

but if there was any issue with brakes that

If there is an issue with brakes that involved ABS, it would NOT be in bleeding the system, and it would not be in replacing pads or rotors.

I didn't want to say that ABS presented no new considerations

Before you make wild speculation or recommendations to someone, I would strongly suggest that you study the subject first.

ABS stands for anti-lock brakes. An ABS system is designed to prevent wheel lockup and try to equalize the rotational speed of the wheels. If one or more wheels is turning more slowly than the other wheels, an ABS system will reduce the brake force on the wheels that are turning more slowly. Every ABS system I have ever seen uses a computer to keep track of vehicle and wheel speed and an actuator which modulates the braking force. ABS systems are a supplement to the vehicle's basic braking system, not a replacement. Contrary to urban legend and uninformed beliefs, a faulty ABS system will not make the car spin around like the girl's head in the exorcist, it will not lock the wheels up, it will not apply the brakes in the path of an onrushing train at a railroad crossing, or toss your mother-in-law through the windshield when braking. If a component of the ABS system fails, then you are left with a vehicle with a conventional braking system that is absolutely no different in braking characteristics from an identical vehicle without ABS.

There are 3 basic components to an ABS system. The electronic control unit, known as an ECU; an actuator, which controls the brake fluid going to each wheel (or axle in more basic ABS systems), and the sensors which measure wheel hub speed. On a vehicle with ABS, the hub has notches that look like gear teeth machined, and as the hub rotates, the notches pass by the ABS sensor. The faster the notches go by the sensor, the faster the sensor sends the on-off signal to the computer. The ECU counts how many times the sensor gives an on-off signal in a given amount of time and calculates hub speed, by which it knows wheel speed. The wheel speed for each corner is compared, and if a wheel is turning more slowly than the others, wheel lockup is implied so the actuator releases the pressure on the offending wheel to let it catch up with the others.

One bleeds brakes to get air out of the brake lines. Because air will compress and fluid will not compress, air in brake lines causes a spongy pedal and reduced force on the caliper or wheel cylinder pistons, resulting in reduced braking effectiveness. Bleeding the brakes has absolutely no connection with ABS.

One changes brake rotors or drums if they are excessively worn or so out of true that they cannot be machined to a true condition. One changes brake pads or shoes if they are worn. Again, pads, rotors, shoes, and drums have no connection with ABS.

bleeding than to suggest that ABS could be completely ignored.

It is even better yet to have some knowledge of a subject before giving advice or speculation or wild guesses that is not even remotely close to being correct.

Reply to
Ray O

I said that backwards. If there is an issue with bleeding the brakes, it would involve the ABS. But, replacing pads and rotors will not cause a need to bleed brakes. And, if air was introduced at the calipers, then the bleeding would not involve the ABS.

I made no wild speculation.

The question was if replacing brake components was different because ABS was involved. The answer to that question is, No.

As a matter of providing more information than was really needed, I suggested that ABS _might_ play a role in bleeding the brakes. I know that in at least one of my cars, the Factory Service Manual says that ABS will present issues in bleeding the brake system. This manual is not for a Toyota product, but it is worth mentioning that the only impact of ABS on brake service will come in bleeding the system.

All of this is all well and good, but when bleeding an ABS valve body, one wants to make absolutely certain that they do not introduce air into the system that can become trapped in the valve body and cause the braking system to not function properly.

This is true to a point, the ABS valve body (you referred to it as "actuator", I have seen several different names and I like valve body because that is essentially what it is) can be a place where air can be trapped. If one can manage to keep air out of the system, then the valve body is of no concern, and then you are absolutely right. But, if one manages to slip and allow air to get into the system, then the valve body - the ABS system - becomes a huge issue; and that is my only point.

I know exactly how ABS works. And when bleeding a car with ABS, many service manuals tell you that the ABS will affect the bleeding of the system because ABS has critical needs relative to fluid bleeding.

It is completely true that one can replace pads and rotors without any consideration of ABS.

Reply to
Jeff Strickland

Here is my original post, by the way.

It's BRAKES, not breaks.

No, the ABS should not change the method of replacing pads or rotors. ABS can play a role in bleeding the brakes, but yous hsould be able to replace pads and rotors without getting into the brake bleeding procedure.

As you can see, all I said was that ABS *can* play a role in bleeding the brakes, but it is painfully clear that I told the OP that he can replace the pads and rotors, and I have to wonder why you are jumping in my shit and kicking so fierciously.

Reply to
Jeff Strickland

Jeff,

Don't take this personally. I was not jumping on your shit, I was just trying to clarify your advice, which, IMO, was a little confusing to the OP.

As you know, there is no need to bleed brake lines when changing pads and rotors. When you mentioned bleeding brakes in your response, to me, it looked like you were saying that ABS might but shouldn't have to play a role in changing pads and rotors.

I thought your explanation was a little confusing so I wanted to clarify that for just changing pads and rotors, whether a car does or does not have ABS is not a consideration. Since you don't need to bleed brakes when changing pads or rotors, ABS is still not a consideration.

Reply to
Ray O

Learn how to quote.

Reply to
dizzy

But he specifically asked about the role of ABS in performing brake service. I told him that ABS played no role in service, EXCEPT that it might play a role in bleeding.

To this I agree. And I thought that this is what I said.

Clearly there are ABS systems where the presence of ABS is an important factor IF brake bleeding is part of the service. I don't know if Toyotas, specifically Avalons, need one to be aware of this considedration or not. But I clearly told the OP that to replace the brake pads and rotors, the ABS is not a factor.

If one has to ask if ABS is a consideration, then it seemed important to me to describe the possible situations where it would be a consideration instead of completely dismissing ABS as a consideration from any sort of brake service that one might attempt. If you are not willing or able to discuss where the ABS system might enter into the considerations for brake service, ESPECIALLY when specifically asked, then perhaps it is you that should think twice about offering up advice.

I gave a two-part answer, the first part specifically addressed the conserns, the second part addressed when his concerns would come into play. Then I told him that he should encounter the second part of the answer if doing the work in the first part.

Reply to
Jeff Strickland

The presence or absence of ABS is not relevant when bleeding brake lines in Toyotas.

I am surprised that the presence of ABS is a factor in bleeding brake lines in any car or light truck. If you think about an ABS actuator, it is like a circuit breaker for each wheel. If conditions warrant, it will momentarily close the valve to a wheel or wheels, then re-open the valve, and if the conditions are still warranted, then will keep repeating as needed. The valves are normally open so fluid just passes through, and the actuator does not modulate pressure to each wheel, just on-off.

If the valves in the actuator are normally open, then fluid (whether the fluid has bubbles or not) just passes through.

If you replace the actuator, perhaps the actuator may have a bleed valve, but otherwise, it makes no sense to me. What vehicle described a different brake line bleed procedure if equipped with ABS?

I guess we'll have to agree to disagree. Since the OP mentioned a 2002 Avalon, my response was relevant and specific to a 2002 Avalon and every other Toyota with hydraulic brakes.

I would not have even brought up the subject of bleeding brakes because not only is it not necessary to bleed the brakes when changing pads and rotors, the presence of ABS has no bearing in doing any kind of brake service on any Toyota unless you are changing the stainless brake lines (different part number).

The second part of your response might have come in to play on the car you mentioned where the presence of ABS changes the procedure for bleeding brakes, but it is irrelevant to every Toyota with hydraulic brakes.

Again, we'll have to differ in advice dispensing philosophies here. When a poster asks a specific question regarding a specific model, I prefer to respond with information that applies to the poster's model. If the another bit of information cannot possibly apply or be relevant to the OP's model, I don't mention it because IMHO, you're giving the poster info he doesn't need or want.

On the other hand, if the poster asks a general question, then the poster deserves a general answer.

Reply to
Ray O

That is the only part of this discussion that I do not know. I will not debate that point because I simply have no knowledge that it is true or false.

momentarily

The presence of ABS is a factor in my BMW, and frankly I would expect it to be a factor in any car. We already know by your experience that it isn't a factor in Toyotas, so clearly my assumption is flawed.

But the actuator is essentially a valve body, and it is crucial that the valve body not trap any air inside. Assuming that air can be introduced easily, then it stands to reason that the ABS has special considerations when it comes to bleeding. Perhaps the same issues relative to air induced into the system apply equally to ABS and non-ABS, and this is your point. But my service manual for my BMW makes a point of telling me that the procedure is different. I haven't actually bled my brakes in my BMW, so I am not sure what the manual is warning me about, but it does warn me and that is all I need to know. When I get around to following the procedure, then I'll pay close attention to the cautions.

You might be right. I don't know what the difference might be, but it really isn't important in the context here. The question was if replacing the pads and rotors was affected by the ABS. I answered, no. Then I went on to say that IF there was any influence of the ABS on brake service, it wouldn't come into play until bleeding of the system. This is a true statement. Now, if upon closer inspection it is found that the ABS doesn't come into play there either, then fine, the statement is still accurate because the qualifier is "IF".

Reply to
Jeff Strickland

If you do not know, then why are you offering advice?

Reply to
Ray O

I didn't.

I said that the ABS does not affect the replacement of pads and rotors. After that, I said that IF there was any influence of ABS on brake service, it would come from bleeding the brakes. Then, I said that there was no need to bleed the brakes if all he was doing was replacing pads and rotors.

And, the presence of ABS is a significant point in the brake bleeding procedure on most cars and trucks. It might not be a significant point on Toyotas, but it is important on others.

Reply to
Jeff Strickland

This looks like advice to me.

How do you know that the presence of ABS is a significant point in the brake bleeding procedure on MOST cars and trucks? One would have to study the procedure for MOST of the hundreds of different models with ABS to know the answer.

This article claims the opposite is true - that ABS is not significant for most, but not all vehicles

formatting link
From looking at the article, it looks like the presence of an ABS pump/actuator in certain Bosch and Delphi units is more relevant if you have changed the pump/actuator or are trying to flush the fluid than if you are bleeding the lines after a caliper replacement. Even if the OP's Avalon was equipped with the "hidden passages" described in the article, the information is irrelevant to changing pads and rotors.

Reply to
Ray O

the information is

This is what I said in the very first post.

The irony here is that the irrelevance is pointed out as the very last thing you said. It was the very first thing I said.

Reply to
Jeff Strickland

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.