Basit06TL

Everytime I press the brake I feel regular pressure as I should, but when I come to a stop and I hold the brake pedal for example at a stop light, about 2 seconds in after im holding constant pressure on the pedal I feel the pedal start to fall toward the floor. It falls about 2 inches or so. I spoke to one of my buddies and he told me to pump the pedal with the car off until it gets solid and then turn the car on and it should remain solid as you hold the pedal down. So I did this but when I turn the car on the pedal drops to the floor slowly. I bled the brakes a few weeks ago alonside my buddy and everything seemed fine up until now. I have no clue what could be wrong. Any ideas???

01tl4tl

What order did you bleed the brakes in?
the TL is diferent than any car I have ever worked on!!

LF Driver FRONT first!! then clockwise around the car
LF RF RR LR

If doing it again doesnt help- you may have a bad master or bad brake booster
When bleeding brakes its crucial not to push the pedal all the way to the floor
a piece of 2x4 will limit the pedal to 2/3 of its travel- too far hurts seals in master cylinder and more

harddrivin1le

It HAS to be air in the lines if the problem began right after you bled the brakes.

Have the dealer re-bleed them.

Why did you bleed the brakes on a 1 y.o. car?

Inaccurate

TSB: 07-041 Brake Pedal Is Low and Feels Soft (click here)

I hate cars

Usually when you have air the pedal is spongy all the time. A bad master would make it fall to the floor when holding steady pressure over time.

Basit06TL

I bled them in the same order thats stated in the Acura manual. I did it because I had alittle over 30k miles on the car and was just doing some preventative maintenance on the car and also decided to bleed the brakes while I was at it. Would bleeding the brakes this one time give me a bad master? Also, If I took it in to the dealer this should be covered under warranty correct?

I hate cars

I thought you bled them because they were soft. I would have to say it's due to air.

Basit06TL

No they became alittle soft a few weeks after I bled them. I was thinking of purchasing a brake bleeder and doing it all over again.

I hate cars

Is it possible you left one of the bleeders cracked open a bit? It might not be a bad idea to inspect each one for leaking brake fluid.

Basit06TL

I think im going to do that since I checked the reservoir and the fluid levels their are fine.

Tansley Services

I am going to have to agree with 01tl4tl on this. Usually a sinking pedal as you describe is due to a bad seal in the master cylinder causing a internal leak. It's not uncommon to ruin a seal when bleeding the brakes if you push the pedal all the way to the floor. See if you can't get it replaced under warranty, just forget to mention the details of you bleeding the brakes.

timmahh

This doesn't sound like your problem.. BUT..

I believe when you come to a stop and your engine hits normal idle you will feel a slight change in the brake pedal; since the engine is no longer running at a high RPM the vacuum used to assist the brakes is not as great, and you will feel a slight change in the pedal

right? I think thats correct.. I don't ever pay attention to it because it's normal =/

Basit06TL

That does sound like my problem. I didn't know our TL's brake system did that at idle.

I hate cars

The theory sounds good except you usually have some type of vacuum reservior and the brakes should have full vacuum all the time. Imagine if you went from very low vacuum (WOT) and had to hit the brakes suddenly. You would have no assist. Mine doesn't fall after holding it at a red light.

timmahh

I'm not entirely sure what it is.. I haven't paid attention to it in my TL but I know it exists on cars.. seems like a common thing..

supadupahyphy

iTrader: (1)

I had the same problem, took it in to the dealer. There they found out after some testing that it was a faulty master cylinder. The part had to be ordered but had it fixed within a week and they let me roll an RDX

Tansley Services

When you have the car turned off, press the brakes a couple of times until the brake gets hard. With the car still off, press it again for 15-30 seconds. Since you have no vacuum with the engine off, if the pedal sinks, you most likely have a bad master cylinder or a leak somewhere, but since you said the fluid levels were full, i doubt you have an external leak.

fjstein01

I am experiancing the issue exact issue with my '96 TL. Were you ever able to indentify cause and fix it?

Thanks!

csmeance

It was posted by supadupahyphy, the fix was to replace the master cylinder for the brakes.

kobi2002

Had the same problem with my 06 before I got my 07 tl-s. The master cylinder was gone. Dealer fixed it and it was stiff like it should be

Basit06TL

The problem seems to have gone away. I dont feel the soft pedal anymore and i've been keeping an eye on the brake fluid levels and they have been fine since this problem arose. Im going to keep an eye on it and pay attention to the brake to see if it comes around again. I don't think I had a faulty master cylinder, maybe just some air in the lines.

01tl4tl

air does not go away on its own- it is trapped in the system if its there

Find the real problem or expect an expensive surprise soon

eluzion

I'm having this same exact problem on my 2004 TL. The brake pedal has always felt pretty soft but recently it's become a lot softer and when I'm sitting at a light with the brake pressed, the pedal moves slightly further in like it's losing pressure.

I'm debating if I should bother replacing/bleeding the brake fluid or if I should just have the dealer check it out. I'm guessing it's either the master cylinder or this service bulletin. I hate going to the dealer...

eluzion

The VSA modulator costs nearly $900... you've got to be shitting me.

I think it's time to sell the car and buy a new one under warranty...

eluzion

Is this a fairly accurate way of determining whether or not the master cylinder is faulty? I'm guessing mine is going bad because when I sit at a stop light, holding the brakes, I lose pressure and the pedal moves a fairly significant amount towards the floor. I've never bled the brakes since I've owned the car so I don't understand how air would entered the system. However, it could be that VSA modulator issue which would suck since I'm out of warranty. It seems like Acura should replace it for free if it's a faulty component that affects the safety of the vehicle.

Has anyone ever replaced their brake master cylinder? I usually do all my own work but I've never messed with the master cylinder before, so I'm not quite sure what's involved. I know the master cylinders run about $130.

Dwest33

I would seriously doubt that this is a true way to test if the master cylinder has gone bad or not. If the pedal goes soft, or bleeds off to the floor, then it has to be either a bad master cylinder or air in the lines. Now, the only way for air to be in the lines is because either you are really low on fluid (and sucking air into the master cylinder) or you have a leak somewhere in the lines. I am seriously doubtful that it has anything to do with the VSA; The VSA senses things such as pedal force, wheel slippage, steering wheel angle to determine if the car is sliding. The car then compensates the sliding by applying brakes to different wheels to compensate (it also controls engine torque for the sake of the discussion). From past experience it definitely sounds like a bad master cylinder. I had a similar experience with an old Lexus; I would be sitting at a light with my foot on the pedal then it would gradually go to the floor. I would then pump it up and then it would repeat.

I also have had the privilege of replacing a master cylinder. The procedure is fairly simple, but could be messy if you aren’t careful (And brake fluid will eat paint off a car like a fat kid eats bacon off a breakfast plate). Some musts are:

You need to bench bleed the new cylinder before you actually put it in the car. This gets the new master cylinder primed so you can actually bleed out the entire system.

Installing it depends on the car but it is fairly simple. Just remove the old but make sure you are careful with spilling the brake fluid in the old MC. I would recommend removing as much brake fluid from the old reservoir as possible. Use a cheap turkey baster, just throw it away when done. If you spill any fluid wipe it up immediately. I would also recommend having a bucket of water/soap and a towel near by just in case.

Installing the new one is just the opposite as removing the old. Like I said, just make sure the MC bench bled before installing. When done bleed the system so no air is left in the lines.

When bleeding the system, bleed each wheel starting from the wheel farthest away from the master cylinder (back right), and then moving to the next closest wheel until you have all the air out of each line. I would get several bottles of brake fluid. I would also recommend getting a check valve if you are going to bleed the system your self (this isn’t absolutely necessary but sometimes if you have a lot of air in your lines it could be pretty frustrating). All this does is ensure the air and fluid is moving in only one direction and isn’t oscillating back and forth.
I would also recommend getting a full repair manual for your car. They are really helpful. Good luck.

nfnsquared

No!!!!! Proper bleed sequence for TL is LF,RF, RR, LR. Or in other words, start at the driver's side front wheel and move clockwise.

eluzion

There is a service bulletin (posted earlier in this thread) that suggests the VSA modulator can be faulty and allow air to enter the brake system.

With the car off, I pump up the brake pedals and hold it. If I press the pedal with a decent amount of pressure, the pedal will press in further. However, with a "normal" amount of pressure, it pretty much stays put. I'm guessing the pedal shouldn't move at all, regardless of how hard I press the pedal?

I'm guessing/hoping it's either a bad master cylinder or air in the system. I'm doubting it's air in the system because I haven't touched anything in the brake system and I don't see how air could have magically entered.