Brake Light behavior: I need your help!

[TripleTransAm]

My visit to the dealer to get the brake booster changed was unfruitful.

My brake lights still go out prematurely as I decrease pressure on the pedal.

The technician asked me to ask y'all how your Marauders behave, since the Grand Marquis brake booster is a different part number and behaves differently.

With the back of the car facing a reflective surface (even some monochromatic wall will do), we'd like to know at what point in the pedal travel you see the brake lights go off.

In my case, the brake lights come on instantaneously the *moment* I touch the pedal, and stay on until max travel. Then, when I begin to release pressure off the brake pedal, the lights will be off as the pedal travels upwards, and *may* come back on if I cease to let off on the pressure. They definitely come back on if I re-apply pressure anywhere during the travel.

The technicians both agree that the brake light switch ends up opening because the pedal manages to ease up pressure on the brake switch since the brake booster shaft has a lag in fully extending itself past midway.

I'm assuming that since no mention was made of the master cylinder during all this investigation, that it is functioning properly.


So, any feedback you guys and gals can give me on how your brake pedal + taillights behave in the above scenario will help me in solving this problem. I'm fairly jittery about this because of the amount of time I spend in stop-and-go traffic each day, and how many times I've had a truck lurch forward almost into my back bumper because they thought I was about to move because my taillights went out even though I still had my foot nicely on the brake!!

[MMM2003]

What is: "break"??? (I had to do it, sorry don't mean to get off subject/topic)

Seriously, I'll check tonight, when I get home. From memory I'd say, mine doesn't do that. Brake light comes on at lightest touch and stays on, until foot is off. I notice this, due to leaving at dawn, with the rear facing the closed garage door.

But as I said early, that's from memory. I'll double check tonight and let you know !

[jgc61sr2002]

Sounds normal to me. If there is a problem I would think it is the brake light switch. John

[TripleTransAm]

Originally posted by jgc61sr2002
Sounds normal to me. If there is a problem I would think it is the brake light switch. John


That's where we're having a hard time figuring things out... the brake switch is plenty sensitive. I just have to lightly touch the pedal and the lights will come on. Very nice, no problem with that. But yeah, the switch sounds like a plausible culprit (and was my initial complaint to the dealer).

Sensitivity is not an issue:
It's that when I'm REMOVING pressure off the pedal, and the pedal is moving upwards... the brake lights are probably off. No big deal if I'm actually removing my foot from the brake, but if I stop releasing pressure and keep a steady brake pedal application, I can actually get into a situation where the lights are off but I may still have the pedal depressed a good solid 1/3 to 1/2-way!

In other words, I brake, lights on. Okay. Now I begin to let up on the pedal slowly, without ever removing my foot off the pedal. Lights will probably go out at some point during this travel! If I stop letting up on the pedal, the lights might actually remain off! If at any point during the 'letting off' movement I reapply any sort of pressure on the pedal, the lights come back on.

The way it was described to me was as follow: it appears the brake switch is somehow compressed between the booster shaft and the pedal linkage. During application of the brakes, the switch is compressed between the linkage and shaft, and the lights come on. If I allow the pedal linkage to rise off the switch, the booster shaft will lag in keeping the switch compressed by mid-travel... that means the gap between the pedal linkage and the shaft will be sufficient that the switch breaks contact and the lights go out.

So if it is a faulty switch, it needs to be sensitive enough to trigger right away on compression during brake application and needs to remain sensitive enough such that even if some gap occurs between the shaft and the pedal linkage, the contact won't be broken.

Actually, after writing the previous paragraph, it all sounds so much like the switch is at fault. But the technician told me it wasn't a simple matter of push-pull, so I don't know if I'm oversimplifying the function of this brake switch. *sigh*

Again, thanks for the helpful hints... keep the brain juices flowing.

[Mark McQuaide]

Steve, I just went out to the garage and checked mine. The lights stay on throughout the pedal travel, as you would expect.

[Murader03]

Just checked mine. The brake lights come on and stay on as long as pressure is being applied to the pedal..The minute I start to relax the pressure, the lights will go out, and stay out uintil I again start applying pressure. The slightest action on the pedal will cause the lights to either cycle on or off. Likewise, if I depress the pedal and then stop the application of breaking pressure, the lights go out.

Gee, if this is in fact a defect in something, then besure to let us all know. I'll chek my wife's FMC product when she gets home tonight. I can't remember if my old Mustang or CV did this.:confused:

[SergntMac]

Could lead to a rear end collision in bumper to bumper traffic, I hope they diagnose this ASAP. BTW, checked mine, A-OK.

Thanks for posting /Steve, it's the little "nonsense" things that can lead to dangerous situations.

[MI2QWK4U]

I just checked mine in the garage, nice and dark so it was very easy to see the lights. After applying the brake, the second I began to slowly let off the pedal, the lights would go off. Tried it several times, even if I stopped letting off the pedal, and maintained the pressure, the light stayed off, got a range of postions, anywhere from 1/3 to 1/2 and the lights were still off. ONLY when i added the least amount of pressure would the lights come back on. In some cases, depending how slowly I let off the brake, the lights would flicker on and off.... Definetely needs more looking into. None of my other cars in my sig behave this way, cause I just checked them all, and for the most part all of them, the brake lights went off when I was about 90% off the pedal. Any thoughts?

[TripleTransAm]

BINGO!!!

THANK YOU guys for sharing your experiences... you all managed to describe EXACTLY what I've been attempting to do. It's really tough to describe in words how to reproduce it, but from what I've read, you have managed to experience what I'm up against.

My worry is indeed as Sarge mentioned... getting rear-ended in bumper-to-bumper traffic. Since the primary reason for buying this car was its safety features, this problem totally goes against this car's purpose in my household: protect my family at all costs.

The Grand Marquis we tried exhibited a slightly similar behavior, but it was only finicky at the top 1/3 or 1/4 of pedal travel... at that point, on a Grand Marquis, you're probably not braking all that much anyway. But with the MM-specific brake booster, you now have this 'dead spot' occurring at 1/2 travel, and the brake switch can't keep up!!!!

I don't know where to go from here... the dealer said no reports exist relating to this fault, and I'm pretty much the first. As long as this remains the case, Ford will most likely just tell me to go get stuffed instead of addressing this...

Once again, thanks to all!!!!!

[MI2QWK4U]

Well Steve, It seems to me that we need to report this problem to the dealer and get it on record. Maybe something will show up on OASIS as a result?

[gonzo50]

Originally posted by Murader03
Just checked mine. The brake lights come on and stay on as long as pressure is being applied to the pedal..The minute I start to relax the pressure, the lights will go out, and stay out uintil I again start applying pressure. The slightest action on the pedal will cause the lights to either cycle on or off. Likewise, if I depress the pedal and then stop the application of breaking pressure, the lights go out.
Mine does the same here as yours, Murader03.

[Blue Marauder]

Checked mine tonight. They appear to work normally. Right after they went off my wife said that her foot was off the pedal. Could this be a 300A vs 300B problem. Mines a B, obviously.

[TripleTransAm]

Originally posted by Blue Marauder
Checked mine tonight. They appear to work normally. Right after they went off my wife said that her foot was off the pedal. Could this be a 300A vs 300B problem. Mines a B, obviously.

Mine is a Canadian A, otherwise known as a B. ;)

Build date Feb 13 2003.

The best way to test this scenario we're analysing is to sit in the driver's seat and have someone else check the lights... that way you can be the one to determine how much pressure and in what direction when the lights do go out. Have the witness call out when the lights go on or off, and then you can be the judge of whether it correlates properly with what you're doing with your foot.

Remember, best results (!) are obtained when removing pressure from the pedal in a gradual fashion, while never really lifting off completely.

I've already made a note of this problem with my dealer, so anyone else who wants to raise heck with their dealer over this, be my guest, there's strength in numbers, we have to be heard. Otherwise, as far as Ford is concerned, there IS no problem.

[jgc61sr2002]

TripleTA - Can you get hold of another Marauder and compare the brake lights. ( at the dealer or a local one) I think that would clear up the problem. John

[DLoreanMARAUDER]

went out and checked mine and found some interesting results!

1-. ok with the car OFF, lights go on when pedel is pressed and go off when pedel is fully released.

2-. with car ON but IN PARK/N. lights come on when brake is applied but go OUT when i begin to depress (like what you describe). seams dangerous BUT......

3-. whith car on and in DRIVE/REVERSE. the lights go on when Brake is applied, but upon depressing the lights will flicker once and stay ON untill pedal is FULLY depressed. I tried this 2 ways. 1-hold parking brake in D/R and slowly release pedal, and 2-idle in D/R and slowly relaes pedal. both reacthed the same as stated above.

Question is did people try it with the car running or off? and second Question is TransAm, does it still happen with the car in DRIVE/REVERSE?

My car is a 300A (8/22/03 build date)! hope this helps and we can get to the bottom of this. in my car i see only a problem if im in P/N, but while in all driving gears car seams perfectly safe.

[DLoreanMARAUDER]

oh yea one quick note, My dads 2000 chevy suburban did the same thing described! while driving if i would depress the brake the slightest bit the lights would go out! I rember sitting stopped in traffic and seeing the lights go on and off in the reflectionof the car behind me. BAD CHEVY........DANGEROUS!

but like i said in my previous post My MM will react like this in PARK but in drive/R the lights stay on throught full pedel travel

[TripleTransAm]

Originally posted by DLoreanMARAUDER
does it still happen with the car in DRIVE/REVERSE?


I'll double-check tomorrow but I'm fairly certain it acts the same way, if not slightly better. I was checking out the new booster by watching the reflections off the dealership window, and I'm pretty certain I was always in gear.

There's a good explanation for the Park/Drive change in behavior. The 'lag' in the booster shaft is what causes the switch to go open. The brake booster uses vacuum assist to boost braking pressure on the brake master cylinder piston. So with the engine on, there's vacuum assist, with the engine off the vacuum assist eventually goes away with a few pumps of the brake pedal.

So it seems that the 'lag' is more apparent when the booster is 'working' (ie. receiving a vacuum signal).

[Blue Marauder]

[QUOTE]Originally posted by DLoreanMARAUDER
[B]My car is a 300A (8/22/03 build date)!

Your car is from the future?!?!?! So Einstein was right. Time travel is possible.

[Murader03]

I checked this again this morning at work. Backed up to a large plate glass window. Thr brake light will "stay" on continously, as long as there is pressure on the pedal when the engine is off, no vacuum. Now another concern! With the engine on, it operates as previously stated at the beginning of the thread, and my earlier check on this. Now the new....

With the engine on, I can very gently press the brake pedal all the way down, max travel, and never get the brake lights to come on. Something isn't correct in this setup. Guess it'll have to go to the dealer and see what's up. I was suprised that I was able to apply the brakes, although very gently, without the lights coming on!:nono: Not good!

:confused:

[Mark McQuaide]

If the brake lights are on when the car is decelerating, it should be OK - maybe it's designed that way.

[Macon Marauder]

Mine behaves similarly to 3TA's:

Depress pedal, lights come on.

Slowly let off, lights go off/on until pedal all the way up - then off.

But, it seems to me, in order to get the "flicker" I have to depress the pedal a pretty good bit. That is, in normal driving I don't press the pedal that far. Maybe in a panic stop?

So, on the way home last night I'm watching my brake lights glow in the rear view and I see NO FLICKER. I touch the pedal: they come on and I keep pressing until the car stops. I release the pedal slowly and they stay on until all the way up.

My point? Sitting in the parking garage I can duplicate this problem. On the road, I can't. At least not yet.

- Rob

[TripleTransAm]

Originally posted by Macon Marauder

My point? Sitting in the parking garage I can duplicate this problem. On the road, I can't. At least not yet.


I'm noticing a similar behavior pattern... unfortunately, stop-and-go bumper-to-bumper traffic is functionally the same thing as sitting at a complete stop in a parking garage, so I'm still up a creek. :(


I did notice one thing this morning. With the changed booster, it appears to be *slightly* improved while in gear. I tried the 'emergency brake on' brake light test that initially alerted me to this problem, and the 'dead spot' appears to be closer to 1/3 of the travel instead of the previous 1/2. That means the 'flicker' only occurs when relieving pressure above the upper 1/3 of the pedal travel. The Grand Marquis we tested yesterday exhibited the same behavior, with its different brake booster.

However, I will try to reproduce the 'complete brake application without brake lights' that was just now reported. That sounds much more dangerous overall.

Why didn't Ford just go with a simple distance-related switch? Depress the brake pedal, the switch closes, you get lights! Why all this funky pressure-related stuff?? I can imagine how crazy this brake light situation will get once we start wearing out brake pads and ending up with low brake pedals, that should REALLY mess up our taillight situations. Or in a high age vehicle with a "tight" booster shaft (due to rust or lack of lube). I just can't understand why they did this...

[Blue Marauder]

Double checked mine tonight when my wife and I went out to dinner. They operate normally under all conditions. I don't see how it could make a difference whether you are in park or drive/reverse. Perhaps there was a batch of faulty brake light switches?

[TripleTransAm]

Originally posted by Blue Marauder
I don't see how it could make a difference whether you are in park or drive/reverse. Perhaps there was a batch of faulty brake light switches?


I was thinking about that yesterday. I suggested the engine on/off difference was due to vacuum assist in the brake booster (ie. no vacuum / no assist with engine off), and as for the park or drive/reverse difference, I think it has to be vacuum as well. In gear the car idles at just over 500 RPM but in park it idles a little higher. This changes the vacuum available at the booster, and probably changes the booster's behavior (ie. amount of assist).

After all this debating and experimenting, I'm starting to think it's a combination of brake switch and booster problems. After the booster change, it seems almost like the problem has decreased in intensity. I used to be able to detect the brake lights going out in traffic by checking the reflection off the truck behind me, but it's almost like it's improved over the two days since I've had the new brake booster in the car. Perhaps the new booster has 'broken in' and is now behaving closer to spec. If anyone's going to get this looked at, have them observe the brake booster behavior very closely... it takes careful attention to spot the 'floating' shaft problem.

I'll keep an eye on this every so often and report whether it improves or not.


I said it before and I will say it again... I cannot thank you all enough for all the feedback you've given me on this issue. I hope those of you with the same problem will get proper resolution from your dealer as well.

[TripleTransAm]

I've had a few weeks to evaluate the behavior of my brake lights since the brake booster swap-out, and I definitely see an improvement.

Right now, the only iffy situation is when I ease off the brakes slightly after a forceful or panic type of braking action... the brake lights will go off momentarily as I ease up, but it's no worse than a long flicker rather than going completely out.

In almost every other situation, I only manage to get the brake lights to go off when I'm somewhere near the upper 1/4 of the pedal travel, and by then the car seems to be starting to move already. So I'm definitely okay with this behavior.

So it was either the new brake booster having had time to 'break in' or they jiggled the brake switch into behaving better, somehow. I don't care, I'm just glad to have 'normal' brake lights once again. If we hadn't had a resolution to this problem, I'd have certainly resorted to http://66.227.101.70/contrib/paladin/jesse4.gif

I'll be passing on the results to my dealer tomorrow. You folks with the same problem might want to get it checked out.

I just remembered something curious... when I took some cousins around the neighborhood for a ride, my cousin remarked something about the car feeling like the brakes weren't releasing on time. I ignored the comment, thinking how on earth could someone in the passenger's seat detect something like this? Maybe the guy was on to something after all!! http://www.handykult.de/plaudersmilies.de/rough/stab.gif

[RCSignals]

I'm glad it seems to be working right now.
All this mystery was starting t make my head hurt :help: