Chad05TL

Has Anyone noticed that in an emergency if u have to hit the brake hard and fast that the pedal wont go down immediately? Like it has to let wait a half sec before it will collapse down and apply the brakes. I truly hate that. In fact it sort of presses against you until the pressure releases and then it goes down. Like TOO LATE ACURA.. HELLO..

Like the faster and harder u hit the pedal the more it locks up. Thats dangerous because u cant stop if someone does something stupid in front of you. Like hit the brake or cut over into your lane. That happens a lot in dallas.

polobunny

What?

My brake pedal feels fine, like any other car I've had before, there's no delay between me pressing the brakes and the brakes applying. Are you sure you don't have air in the lines?

Chad05TL

Normal driving the brakes are great. Even aggressive driving everything is great. But just get an open parking lot and stomp on the brake.. I bet u have a lag and dont know it.

Chad05TL

Besides.. Air in the lines would cause a soft or spongy brakes. Not a hard brake pedal. Also note: this is only if I stomp on the pedal. I mean really stomp on it. It takes half an inclination to compress. No problems under normal quick braking. So literally i mean stomping on the brake pedal.
See below. Hard brake pedal
http://www.aa1car.com/library/bfixes.htm

Oh Sickest TL

iTrader: (3)

?? i think you may have something going on in there that YOUR not aware of lol...my brakes never feel that way??

Nova_brad

That's definitely not normal. Mine doesn't do that either. Sounds like a booster issue, in the link provided above, read the part about the booster test...

----
A quick way to check the vacuum booster is to pump the brake pedal several times with the engine off to bleed off any vacuum that may still be in the unit. Then hold your foot on the pedal and start the engine. If the booster is working, the amount of effort required to hold the pedal should drop and the pedal itself may depress slightly. If nothing happens and the vacuum connections to the booster unit are okay, a new booster is needed (the vacuum hose should be replaced, too).

t-rd

You might have a problem with the master cylinder?!

ZOMGVTEK

I'm not sure why everyone else claims to not notice this. I've noticed it on every car I drove with power brakes, some to more of an extent than others. It's kinda just how vacuum assist brake systems have always worked.

It's not that the brakes don't work, or have some delay, they don't. It's just that the available vacuum assist is reduced when you smash the pedal. The small delay you're noticing is the running engine creating more vacuum, assisting the pedal. Basically, you're not pressing hard enough. If you press the pedal much harder initially, it will work like you expect. It could be when people panic brake they slam on the pedal and thus would get sufficient travel, or they just don't notice. Personally, I find it to be very easy to anticipate how much power assist will be available based on the brake pedal acceleration. If you need to slam all the brakes right now, you can't lightly press on the pedal, slam on it. Although be aware, ideally you would only press the pedal enough to brake to just under the max ability of the tires, once they lock up and the ABS kicks in, its going to take a considerable amount more space to slow down.

With that said, it SHOULD be rather uncommon when you need to worry about panic braking. Increase your following distance to something a bit safer.

polobunny

That's like exactly the opposite of what OP is describing.

Chad05TL

oops I deleted what I typed. I think I was responding faster to email or something. Like I got ahead of you, or something. haha

but yes.. I was not too surprised to hear the comments from other people saying "it must be Only my car" because people simply don't know this has been a problem for a long time with power brakes. If you stomp on them, they really don't work. I was pressing very hard, then all of a sudden they worked hard! So, it took a sec for it to react. But I just about hit that car because she pulled over in my lane.

ZOMGVTEK

Pump the pedal a few times with the car off. You will feel the assist on the first press or two, then the pedal turns into a brick. You may notice a small area on the initial travel where the pedal moves, but no braking is actually occurring. It can help to have the car rolling slow in an open lot to get a feel for the effort required. Just be aware you need to pump the brakes a bit after the engine is off to remove the assist. Small movements at the top of the range can help this without doing much real braking. Practice common sense, and be aware you still have the hand brake available. Although it's not terribly powerful, and I hear some people are unable to pull it hard enough to do much.

Power assisted brakes without power assist are harder to press than systems designed to not be power assist. If power steering fails, people think they can't steer since its difficult to move the wheel, same with brakes. Just turn harder and brake harder, they work. I think everyone driving a car should have some idea of what effort is required to turn and stop should the power assist go away for whatever reason, which will happen if the engine stalls.

Chad05TL

I have drivin my grandfathers old truck a long time ago, and didn't have a problem with non-power brakes. I cant press any harder than stomping on the brakes. If the pedal freezes up then it freezes up. Not much else to say. This TL may be worse than other systems even though it is "normal" to have much resistance under emergency conditions. Serious, I challenge anyone to go out to a parking lot and hit the brake like you are trying to break it. And watch it lock up on you. haha In fact, the harder you hit it, the more it will resist.

ZOMGVTEK

Like I said, the older systems that were designed around not having power assist are easier to brake than a modern power assist system without the assist. When you death stab the brake pedal, you're essentially asking for assist faster than its available. It's very hard to get the brakes to bite as quickly as you want some times. The harder you press, the more it does 'fight back', and the more effort you need to put in to overcome this. It can be done, but the pedal and mount flexes a lot.

The brakes do work in the mean time, I assure you. You need to provide a lot of effort. My current daily driver has a power brake system without power assist, and a power steering system without power assist, and at this point I mostly forgot about how easy most cars are. However, I'm quite familiar with what you are describing, and providing consistent feel in the brake and steering is why I removed power assist. This isn't on my TL, however. That things too damn heavy to drive around without power steering given its somewhat quick rack and smaller wheel.

Exchanging the brake fluid through all the lines and VSA modulator is a reasonable idea, especially if its never been done.

Chad05TL

ok thanks.. I pretty much knew that, but I wanted to hear it from the pro's and maybe a more technical review of it, and also mainly to say that this TL seems to be worse about it than other cars I have driven. Either that or my reflexes are faster at middle age than they used to be when I was younger. haha Either way, it doesn't pay to have to need to smash on the brakes fast and expect the car to respond equally as quickly.

Chad05TL

I installed the oem shims. There are 4 big shims per side on the front compared to the 2 small ones I had installed that came with my brake pads. Now my pedal feels softer. Softer is the direction I needed to go. Maybe this will help the symptoms I mentioned above. I know they already feel better but I have not had to test them in an emergency. So now I am like totally oem.

I hate cars

This is exactly right. There can be a slight delay in the power assist when you slam on the brakes violently. The brake system still responds instantly but it takes a little longer for the assist to arrive. There's really nothing you can do about it, it's the way the system is designed and it's functioning properly.


As to the last post, softer is never better in a brake system. By installing a bunch of shims you've made a slightly compressible spot similar to having a little air in the system except the brakes will apply as soon as you hit the pedal but the pedal will move more than normal. Still not good and completely unrelated to the original problem.

csmeance

Your brakes sound messed up.

Flush the brake fluid COMPLETELY from the canister and as well all 4 calipers and lines. You may need new brake lines if yours have a bubble/damage to them. The fluid should have NO MOLD on the top when you open the cap before replacing the fluid. If there is heavy mold or the fluid is dark, you may have a larger issue on hand.

Check the master cylinder for leaks

Remove all pads and compress the pistons and verify all gaskets are good, slider pins are lubed, etc.

Buy new brake pads while you have everything apart. Autozone CMax gold has free lifetime replacements. Bring your worn ones in and you get new ones for free. They stop almost as well as OEM and have zero dust.

Measure the rotor thickness and verify that they are above the service limit. People like to put on Hawk pads that chew through the factory rotors, then replace only the pads again and again until the rotor is past the limit spec. The thinner the rotor, the farther you need to press the pedal. Same with worn pads.

Remove those extra shims, they should not be there.

Chad05TL

thanks..


it all works fine now..


peace out..

I hate cars

No it doesn't.

justnspace

iTrader: (1)

in two weeks, we'll have chad come up with another thread about brakes and springs titled;

"my aspec springs are not braking!!"

rockstar143

iTrader: (6)

The shims could not have made the car react to a violent braking better. That's impossible.

thoiboi

Chad

justnspace

iTrader: (1)

rockstar143

iTrader: (6)

Logically, this can't make sense to you Chad. It just can't. If anything you might have eliminated a little clearance and you'll end up causing friction and early warping. Honda rotors don't need a lot of help in that department already, if you know what I mean.

Majofo

Chad is looking for professional insight, not amateur night. He obviously knows more than all of you, because he's an engineer.

justnspace

iTrader: (1)

his questions are thought provoking and insightful. very helpful to an inujnear like myself.

rockstar143

iTrader: (6)

I'm a professional carpetmuncher

TacoBello

Wtf did I just read?

1. Why are you driving in such a manner where you have to absolutely slam the brake pedal? In 14 years of driving, I think I did that once. When I was 16 and a complete tool. Learn to drive. Learn to look ahead. Learn to be a proactive driver, not a reactive one.

2. Adding shims has not fixed your problem properly. This is an inherent problem with ALL modern cars these days. The fact you went out and continue testing your brakes to the limit baffles me. Do your tires also make a "tuga-tuga-tuga-tuga" sound now? That would be the flat spot you now created on your tires by hammering the brakes for no apparent reason.

3. I'm glad you created a thread asking for help and then COMPLETELY and utterly neglected all replies provided to you, and went out and did your own back yard fix by putting additional, flimsy metal shims in place to fix something that isn't even a problem.

4. Wow. Just wow.

5. It's Acura's fault for you surpassing the limits of a mechanical system but you know, non-power brakes are MUCH better this day and age.

Majofo

My guess would be a master cylinder locking up from an overpressurized brake booster. Essentially the brake booster isn't keeping a linear vacuum and is resisting the action of the brake pedal versus assisting in the braking. Adding shims will help to make braking more linear, but to resolve the issue, OP should remove the brake booster, check the spec on the relief valve and the vacuum line. If that all checks out, reseal the booster and check the vacuum inlet from the tb intake manifold side. Checking CFMs, a consistent vacuum should be observed. When panic braking, be aware that the relative vacuum is proportional to the throttle applied. If you are accelerating hard, you will have an inversely proportional vacuum, thus stabbing the brakes will have less assist than idle. But OP is having the opposite issue, which is what would essentially happen if it were overpressurized (resist in the brake pedal but delay in braking). If the booster all checks out, check the master cylinder. Years of use, with consistent exposure to moisture and the development of algae growth, could have made the valves sticky. The hydraulic action thus is being resisted. You're essentially feeling the delay and harsh feedback from the action of the MC. Drain the MC, remove it, clean it out and manually check the movement of the valves. If it feels gritty, change the seals on the main valves (moreso on the front valve) or replace it all together. Also replace the vacuum line since a collapsed line could also lead to pressure issues. /txt

rockstar143

iTrader: (6)

You finally post something useful and you waste it on THIS!

Majofo

bruh

rockstar143

iTrader: (6)

No. I don't even.

thoiboi

ffa

rockstar143

iTrader: (6)

I actually agree. I did a little research of my own and my guess would be a master cylinder locking up from an overpressurized brake booster. Essentially the brake booster isn't keeping a linear vacuum and is resisting the action of the brake pedal versus assisting in the braking. Adding shims will help to make braking more linear, but to resolve the issue, OP should remove the brake booster, check the spec on the relief valve and the vacuum line. If that all checks out, reseal the booster and check the vacuum inlet from the tb intake manifold side. Checking CFMs, a consistent vacuum should be observed. When panic braking, be aware that the relative vacuum is proportional to the throttle applied. If you are accelerating hard, you will have an inversely proportional vacuum, thus stabbing the brakes will have less assist than idle. But OP is having the opposite issue, which is what would essentially happen if it were overpressurized (resist in the brake pedal but delay in braking). If the booster all checks out, check the master cylinder. Years of use, with consistent exposure to moisture and the development of algae growth, could have made the valves sticky. The hydraulic action thus is being resisted. You're essentially feeling the delay and harsh feedback from the action of the MC. Drain the MC, remove it, clean it out and manually check the movement of the valves. If it feels gritty, change the seals on the main valves (moreso on the front valve) or replace it all together. Also replace the vacuum line since a collapsed line could also lead to pressure issues. /txt

I hate cars

The problem here is every power assist brake system will do this. It's not when you hit the brakes hard. It's when you hit the brakes fast. It's pedal speed that makes this show up. The booster can't always offer assist or the brakes would be stuck on. I've had this happen and the only way to get them to release is to go full throttle until all of the vacuum finally bleeds off. This is not what Chad is talking about.

What's going on is the booster's reaction time. It reacts very quickly and its usually not noticeable that there's a lag in boost because you're not hitting the pedal quick enough to notice. Again, I'm not talking about hitting the brakes hard. To try this, kick the pedal. Have your foot already moving fast by the time it hits the pedal. Resting your foot on the pedal and then hitting it hard probably won't produce the lag.

The brake system is working fine. You're just without boost for a few milliseconds. The pedal is hard because there's no assist. Even though it does not feel like it the brakes work from the first millisecond you hit the pedal but the pedal is hard and since there's no boost they're not stopping as hard, people think the brakes don't work for that split second.

Also, if there's any sort of leak or the check valve is not working or is leaking, hitting the brakes immediately after heavy throttle will have a hard or semi hard pedal. Vacuum assist brakes work fine even on turbocharged cars which not only have not vacuum but have pressure. As long as the check valve is holding, you will have full assist even after hard throttle.

The only way to have zero delay under all conditions is to use non power assisted brakes. So instead of a delay before assist comes in, you trade that for more pedal stroke which is a delay in and of itself but not as bad.

Chad is using shims which cause a slightly compressible area which results in a softer pedal which is not what you want but he's too arrogant to listen to people who know more than him. He thinks by causing a softer pedal the problem is fixed which is an assumption and completely unrelated to the original problem.

I'm posting now so that others don't stick a bunch of shims in their brakes if they have a hard pedal and instead they get to the bottom of it.

Majofo

rockstar143

iTrader: (6)

I hate cars

Abs modulator.

TacoBello

Empty your damn inbox!!

rockstar143

iTrader: (6)

His box is perpetually full.