Smoked the brakes yesterday-update on test
Hi Folks. We have a 38' diesel pusher with cummins 350 and Allison trany. Built in 2008 and has 25,000 miles. Yesterday we had a 11 mile, 3500 foot winding, descent averaging about 8%. We used the e...
Forum Discussion
Dan,
First off, another San Diegan huh? Well, I was born and raised there. Lived there 'till 9 months ago, when I finally cooersed the wife to move. We're now in beautiful, Lake Havasu City AZ.
Anyway, your coach, a DP, and all of it's standard programming in the engine ECM, the Trans ECM and the PAC brake, all work together. When descending down hills, if you've "asked" for the exhaust brake, as in following all the parameters, foot off the accelerator and, Cruise control not activated, your ECM will then allow the pac brake to engage.
When it does, it decides what gear to start the descent in, based on your present speed. Normally, if you've not had it re-set, there's a target gear that it will aim for. And that is 2nd gear. That number will appear on the keypad of your trans shift, even if you're starting your descent at say 65 mph.
Ours is completely stock and has never been altered. If I start a descent at around 65 mph, and ask for the exhaust brake, it will take effect but, at that speed, it will only drop the trans to 5th. As the coach begins to slow down, either on its own, or with the assistance of the service brakes, and it reaches between 62-63 mph, the trans will drop to 4th, on it's own.
If the grade is not too steep, that is, the exhaust brake is enough to keep slowing the coach down without the use of the service brakes, it will slow to a point that the trans will downshift to 3rd, on it's own. If the grade is too steep, and it's too much for the exhaust brake to handle, I will of course have to stab at the service brakes enough to slow the coach enough to my liking for it's rate of speed in that given situation and set of driving conditions.
You're driving YOUR coach. To be told to downshift manually without being in your coach, at your speed, doing the driving that you're doing, at the present time, is really hard to do. Each situation is different and, in many cases, is constantly changing, from minute to minute, and almost second to second, based on descent rate, curves, dips, momentum, and a whole host of other variables.
If you've driven this coach for as long as you say you have and, you've been on this particular grade before, then you should know how do descend it without damaging any brakes or other components. Sure, it's possible you'll heat them up a bit, that's a given, in many situations. The exhaust brake is only so strong. It's designed to ASSIST in braking, not do the stopping.
If properly used, it will extend the life of the service brakes by many thousands of miles. Most D/P units that are equipped with either an exhaust brake or, a true Jake Brake (compression style), should see over 100,000 miles on the odometer BEFORE ever needing to touch the service brakes, for brake service that is. This of course does not include leaky seals which, could cause enough saturation of brake shoes do warrant discard prematurely.
But, in your case, as Brett Wolf told you, the "ONE TIME" issue with the stuck emergency brakes is a non-issue with your present situation. It happens to a lot of folks in that situation. It has no effect on wear and, for the most part, have no effect on regular braking.
But, if you "warmed" them up a bit and, generally have not done it before, then it might warrant at the very least, a good, "remove the tires and wheels," brake and drum (if those are the types you have) inspection. I've done that type of inspection on mine, several times. In the pics below, you'll see shoes that have gotten pretty warm descending some serious grades. And, as you can see, there's certainly no warrant for replacement. Good luck and, do pay more ATTENTION while on those grades.
Scott
First off, another San Diegan huh? Well, I was born and raised there. Lived there 'till 9 months ago, when I finally cooersed the wife to move. We're now in beautiful, Lake Havasu City AZ.
Anyway, your coach, a DP, and all of it's standard programming in the engine ECM, the Trans ECM and the PAC brake, all work together. When descending down hills, if you've "asked" for the exhaust brake, as in following all the parameters, foot off the accelerator and, Cruise control not activated, your ECM will then allow the pac brake to engage.
When it does, it decides what gear to start the descent in, based on your present speed. Normally, if you've not had it re-set, there's a target gear that it will aim for. And that is 2nd gear. That number will appear on the keypad of your trans shift, even if you're starting your descent at say 65 mph.
Ours is completely stock and has never been altered. If I start a descent at around 65 mph, and ask for the exhaust brake, it will take effect but, at that speed, it will only drop the trans to 5th. As the coach begins to slow down, either on its own, or with the assistance of the service brakes, and it reaches between 62-63 mph, the trans will drop to 4th, on it's own.
If the grade is not too steep, that is, the exhaust brake is enough to keep slowing the coach down without the use of the service brakes, it will slow to a point that the trans will downshift to 3rd, on it's own. If the grade is too steep, and it's too much for the exhaust brake to handle, I will of course have to stab at the service brakes enough to slow the coach enough to my liking for it's rate of speed in that given situation and set of driving conditions.
You're driving YOUR coach. To be told to downshift manually without being in your coach, at your speed, doing the driving that you're doing, at the present time, is really hard to do. Each situation is different and, in many cases, is constantly changing, from minute to minute, and almost second to second, based on descent rate, curves, dips, momentum, and a whole host of other variables.
If you've driven this coach for as long as you say you have and, you've been on this particular grade before, then you should know how do descend it without damaging any brakes or other components. Sure, it's possible you'll heat them up a bit, that's a given, in many situations. The exhaust brake is only so strong. It's designed to ASSIST in braking, not do the stopping.
If properly used, it will extend the life of the service brakes by many thousands of miles. Most D/P units that are equipped with either an exhaust brake or, a true Jake Brake (compression style), should see over 100,000 miles on the odometer BEFORE ever needing to touch the service brakes, for brake service that is. This of course does not include leaky seals which, could cause enough saturation of brake shoes do warrant discard prematurely.
But, in your case, as Brett Wolf told you, the "ONE TIME" issue with the stuck emergency brakes is a non-issue with your present situation. It happens to a lot of folks in that situation. It has no effect on wear and, for the most part, have no effect on regular braking.
But, if you "warmed" them up a bit and, generally have not done it before, then it might warrant at the very least, a good, "remove the tires and wheels," brake and drum (if those are the types you have) inspection. I've done that type of inspection on mine, several times. In the pics below, you'll see shoes that have gotten pretty warm descending some serious grades. And, as you can see, there's certainly no warrant for replacement. Good luck and, do pay more ATTENTION while on those grades.
Scott
