Turned car off whie coasting in neutral and brakes locked. Why? - Fuelly Forums

Android Users - Coming Soon! - Migrating from aCar 4.8 to 5.0

Go Back   Fuelly Forums > Fuel Talk > General Fuel Topics
Search Today's Posts Mark Forums Read Click Here to Login
Reply
 
Thread Tools Display Modes
 
Old 07-14-2008, 07:05 PM   #1
Registered Member
 
Join Date: Jul 2008
Posts: 1
Country: United States
Cool Turned car off whie coasting in neutral and brakes locked. Why?

I own a 2004 Honda Civic EX, 4cyl, 127HP manual transmission--just in case it matters.

I recently read on the "201 Tips To Save Gas" that you can switch to neutral, turn your car off (not all the way, but to the point where the engine is off and the dash lights remain), and that it will save gas while coasting for long periods of time.

I tried it while using my brakes sparingly and they worked fine. Although bout 3 miles down the road I started to lose brake pressure, the pedal became near impossible to push down, and then I lost my brakes all-together. I quickly started the car and they came back. Why did this happen? Did I do something wrong?
__________________

Sparkatuz is offline   Reply With Quote
Old 07-14-2008, 07:17 PM   #2
Registered Member
 
Join Date: Oct 2006
Posts: 84
Country: United States
Quote:
Originally Posted by Sparkatuz View Post
I own a 2004 Honda Civic EX, 4cyl, 127HP manual transmission--just in case it matters.

I recently read on the "201 Tips To Save Gas" that you can switch to neutral, turn your car off (not all the way, but to the point where the engine is off and the dash lights remain), and that it will save gas while coasting for long periods of time.

I tried it while using my brakes sparingly and they worked fine. Although bout 3 miles down the road I started to lose brake pressure, the pedal became near impossible to push down, and then I lost my brakes all-together. I quickly started the car and they came back. Why did this happen? Did I do something wrong?

great troll- very sly! but i think there is a valid point here. do not sacrifice safety for gas ($) savings. I do find myself cringing at posts that advocate removing wipers and mirrors for millage gains. And turning your motor off can be a problem with vacuum assisted brakes. I personally will not do it.
__________________

mini-e is offline   Reply With Quote
Old 07-14-2008, 07:27 PM   #3
Registered Member
 
Join Date: May 2008
Posts: 140
Country: United States
you have power brakes. my 95 nissan pickup also has power brakes, and after a few pushes, I lose the vacuum but still have brakes, I just have to press harder. a little unnerving the first time, but now I don't think anything of it.
mikehallbackhoe is offline   Reply With Quote
Old 07-14-2008, 09:16 PM   #4
Registered Member
 
GasSavers_JoeBob's Avatar
 
Join Date: Oct 2007
Posts: 698
Country: United States
What the guy above me said. Your power brake booster will save enough vacuum for one or two stops before it is used up. Then the brake pedal will become very hard to push. Unless there is a problem, however, you should still be able to stop. No matter what kind of car you have. I had an '85 Lincoln Continental with anti-lock brakes (the first car to come with ABS standard, IIRC). The pump, a >$2000 part (I only paid $1000 for the whole car!) failed. This pump also acted as the power brake pump. I still drove the car, it just required me to pretend I was He-Man to push the pedal. Eventually I got a junkyard pump for $20 and fixed it.

If you don't feel safe using the brakes w/o power assist, go ahead and let the engine idle while you are coasting. Safety takes priority above all else, even gasoline savings!
__________________
"We are forces of chaos and anarchy. Everything they say we are we are, and we are very proud of ourselves!" -- Jefferson Airplane

Dick Naugle says: 1. Prepare food fresh. 2. Serve customers fast. 3. Keep place clean.



GasSavers_JoeBob is offline   Reply With Quote
Old 07-14-2008, 09:49 PM   #5
beb
Registered Member
 
Join Date: May 2007
Posts: 16
Country: United States
Does your car have ABS? (What car made this century doesn't?) If not, ignore this post. Even if you do have ABS, this post could still be nonsense.

Assuming that 'brakes locked' means 'brakes failed' (instead of unturning tires smoking and screching the car to a hard stop), annother possibility is that the ABS accumulator ran out of pressure. Unlike the absense of vacuum assit, when the accumulator has no pressure, the brakes barely function, if at all, no matter how hard you press; about the only way to reliably engage the brakes in this condition is with the emergency brake.

If the ignition had been left in 'run', this probably wouldn't have happened because the accumulator pump motor would have maintined pressure, but in 'aux' it will just bleed down after enough brake use.

A test of this would be to sit in a (unsloped) parking spot with the ignition in 'run' but with the engine not running (unstarted), and pump the brake pedal several dozen times. Every few pumps, you should hear the accumulator pump motor run (it's usually near the master cylinder, but I've seen it on the firewall near the transmission on a 96 Del Sol), and you should never lose brake functionality (even long after any vacuum has been consumed). If you can ID the sound of the accumulator pump motor occassionally running and the failure is replicated during this ignition in 'run' test, maybe it is vacuum assist causing it instead.

Then turn the ignition to 'aux' (or where ever you had it when the failure occured) and pump the brake pedal several dozen times - this time you shouldn't ever hear the accumulator pump and at some point the brakes should fail in the same way.
beb is offline   Reply With Quote
Old 07-15-2008, 06:19 AM   #6
Registered Member
 
theholycow's Avatar
 
Join Date: Apr 2008
Posts: 6,624
Country: United States
Send a message via ICQ to theholycow Send a message via AIM to theholycow Send a message via MSN to theholycow Send a message via Yahoo to theholycow
As others have said, you run out of vacuum and will need to press the brake harder. As a 220 pound ex-bicyclist in a 3000 pound compact hatchback, I have enough leg power to do a decent job of operating a power braking system that has run out of power, but even then I avoid it. While I feel that the risk is small for me, it's still not acceptable compared to the savings.

Important: If you need to do that much braking, leave your engine ON! EOC (Engine-Off Coasting) is only for situations where you can coast a long time without needing to brake. Either you have not practiced coasting with the engine on, or you are trying to apply the strategy in an unsafe situation.

If you have a long downhill coast without other traffic and just need to keep slowing your car, you could practice pushing hard, or you could occasionally restart it to recharge the brakes. Another option might be to leave it in gear and running; google for "DFCO". Briefly, DFCO (Deceleration Fuel Cut Off) means that the computer shuts off all fuel to the engine while you are engine-braking.

Quote:
Originally Posted by beb View Post
Unlike the absense of vacuum assit, when the accumulator has no pressure, the brakes barely function, if at all, no matter how hard you press; about the only way to reliably engage the brakes in this condition is with the emergency brake.
This runs counter to my experience, common sense, common automotive engineering practices, and probably law. Even if the engine fails, it should always be possible to brake with the daily service brakes on 4 wheels instead of a possibly rusty disused parking brake which applies to two wheels (or on some models, apparently, just one).
__________________
This sig may return, some day.
theholycow is offline   Reply With Quote
Old 07-16-2008, 10:07 AM   #7
Registered Member
 
Join Date: Jun 2008
Posts: 11
Country: United States
Regarding loosing the vacuum on power assist brakes; an easy answer is to tap into the vacuum line with a "tee", plumb in a 1-way valve, and a vaccuum resevoir. I have an old, (1965) industrial truck, (14,000 G.V.W.)where this was done at the factory. Reasoning was, if the engine dies, while going down a long downgrade while loaded, wouldn't have a run-away truck.The tank is about 10" in diameter, by 20" long. It held enough vavuum for 3-4 stops, and this was with 2 slave cylinders per wheel, front and rear, and drum brakes x 4.
I am unfamiliar with ABS brakes, but the previous posters post makes it sound like the accumulator pump runs on electricity, as he says you can hear it go on and off, with the engine off in a parking lot. Should be able to hook up a swith, so you can turn it on, while coastng. If it shouldn't run full time, could wire in a flasher unit, so it goes on and off? As I said, not familiar with ABS, so don't do this on my say so. However, regarding the vacuum resevoir, I KNOW they work! Jim
dutchdivco is offline   Reply With Quote
Old 07-16-2008, 12:48 PM   #8
Registered Member
 
palemelanesian's Avatar
 
Join Date: Apr 2013
Posts: 364
Country: United States
I've seen this same post at CleanMPG and at ecomodder. Looks like a troll to me.
__________________

palemelanesian is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Fleet/Brand metrics? handruin Fuelly Web Support and Community News 1 08-19-2008 02:50 PM
Landspeeds E-bike Conversion (Mk2) landspeed People Powered 5 06-06-2008 08:37 PM

Powered by vBadvanced CMPS v3.2.3


All times are GMT -8. The time now is 05:51 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.