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Clutch in or out while waiting at a light?

I have heard different stories from different drivers on the best practice for driving standard. I had my master cylinder die in 2 consecutive years on my previous vehicle (01 mazda 626) and a friend suggested it was because at stop lights i tend to rest in first gear with the clutch in. Could this "bad habit" be the reason for my hydrolic woes? Is it really THAT big of a deal that i keep the clutch in at stoplights?

Comments

  • edited August 2009
    I don't think the practice of waiting at a stoplight with your foot depressing the clutch caused your hydralic problem, perhaps it did but I doubt it. Still, I don't think it is a good practice.

    With the clutch depressed you are putting pressure on the "throw out" bearing and the yoke that separates the clutch plate from the flywheel. There are some springs in there too that can weaken over time. For this reason my habit over the years is to put the car in nuetral while waiting at a light. If I approach a stop sign or I feel the light is about change to green I will sit with the clutch depressed for short periods. Some stop lights are "longies" and therefore 95% of the time I'm waiting the clutch is out and the transmission is in nuetral.

    I've had bunches of stick shift cars over the years and driven probably a million miles in them and so far I haven't ever replaced a clutch or hydralic master or slave cylinder. I did have a couple of clutch cable breaks.
  • edited August 2009
    That sounds like a poor quality clutch master cylinder. Sitting with the clutch in at a light should not hurt the clutch master cylinder, but it does accelerate the wear on the throwout bearing.

    It does not matter a lot, but if you want to try to ensure that your throwout bearing lasts as long as your clutch, it is best to slip the car into neutral and release the clutch at a long light.
  • edited August 2009
    I agree with the above. A good-quality clutch master cylinder shouldn't be any more likely to fail than a brake master cylinder, and we don't take our foot off the brakes at a light, do we?
  • edited August 2009
    Make this one more vote for NOT keeping the clutch depressed when waiting at traffic lights.

    While this practice is not likely to lead to problems with the brake [b]hydraulic[/b] system, there are other factors to consider. In addition to putting additional stress on the clutch throw-out bearing, I can give you another reason for not doing what you have been doing! While you are sitting there with the clutch depressed, if another vehicle happens to "tap" you from the rear, there is a real chance that your foot will slip off of the clutch, and that might cause you to hit someone else waiting in front of you.

    With two valid reasons for not keeping the clutch pedal depressed at traffic lights, I am confident that you will modify your habits.
  • edited August 2009
    I don't think the master cylinder problems are related to your practice of waiting at lights with the clutch depressed. However, it's still a bad habit you should try to break.

    When I was younger I always waited at lights with the transmission in gear and the clutch depressed. But when I learned more about the additional wear on the throw-out bearing I taught myself to shift to neutral and release the clutch, which is my practice now.

    It only takes a few days to get used to it.
  • edited August 2009
    I aways sit with the clutch depressed and with the transmission in first gear. Saved my butt a couple times. Once while sitting at a snow covered intersection, a person tried making a right hand turn on the street I was waiting on. When the vehicle started sliding straight ahead halfway thru the turn and headed for the back of my vehicle. I just let the clutch out and moved about a foot forward and the vehicle just missed mine and slammed into the snow bank.

    Another time I was waiting at another intersection on a rainy day. I then looked in my rear view mirror and could see a vehicle coming way too fast to stop in time. Again I just let the clutch out and turned around the corner. The vehicle slid through the intersection and got broadsided by another vehicle. So, I'm always ready to get the hell out of the way if I have to when driving a manual transmission.

    But here's another thing to consider. Each time the clutch is operated, there's slippage between the clutch disc, pressure plate, and flywheel. And this slippage is what wears out a clutch. The throwout bearing, also called a thrust bearing, is designed to handle the lateral load imposed on it. So you're more likely to wear out the friction surfaces of the clutch by operating it more times from taking out of gear and then putting it back into gear before you'll wear out the throwout bearing from sitting at stop with the clutch pedal depressed.

    Tester
  • edited August 2009
    For me it depends on the conditions.

    If I am sitting at the front of the line at a red light, I will put it in gear and keep the clutch pressed. You don't want to keep people waiting after the light turns green. If I am second or third in line, but I can't see the light (because maybe I am behind a truck), I might keep it in gear as well.

    If I am sitting more than a few cars back in the line at a red light, I will put the car in neutral and take my foot off the clutch. There will be plenty of time to see the light change and get it in gear before the cars in front of me start moving. The same goes for being second or third in line if I can see the light change.

    If I am sitting first in line at a long light, but I can see the green and yellow lights facing the cross traffic, I might take it out of gear. When the crossing traffic light turns yellow, I have time to put it in gear before my light turns green.

    Sitting with the car in gear with the clutch pressed isn't a good habit, but considering the minute amount of wear that occurs when you do it, it isn't a big enough problem to keep people waiting while you shift into gear. Just plan ahead when you can, and hold it in gear when you can't plan ahead.
  • edited August 2009
    Keeping the clutch pedal depressed at stoplights leads to premature wear of the release bearing (also called the throwout beraing). It could also have contributed to your failed master cylinder.

    Whenever the pedal is depressed, the master cylinder pushes fluid to the slave cylinder which, under pressure, forces the release bearing against the spring-loaded radial "levers" of the pressure plate assembly, lifting the prssure plate and allowing the clutch plate to no longer be "clamped" to the flywheel. Everything in that system is under load.

    In addition, remember that the pressure plate assembly is bolted to the flywheel and continues to spin with the engine. That means that not only is the release bearing under axial load, but its outside race is spinning while its inside race (on the tranny input shaft) is stationary.

    In short, when you hold the pedal in you keep the reelease bearing in its loaded state and the master and slave cylinders and their O-rings fully loaded. Keeping things loaded wears them out faster than letting them unload.
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