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Old 03-17-2008, 04:36 PM   #1
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I was wondering if I should leave my exhaust brake in the "on" position while traveling on a level interstate or just when I antissipate a stop
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Old 03-17-2008, 04:36 PM   #2
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I was wondering if I should leave my exhaust brake in the "on" position while traveling on a level interstate or just when I antissipate a stop
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Old 03-17-2008, 04:44 PM   #3
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Neither. The brake is used when decending long grades or whenever a high use of the service brake is encountered. The diesel has no compression braking, like a gas engine. The brake is used to slow the coach on decents where use of only the service brake may not slow the coach.

On level or rolling interstate highway, my brake is off.

I do switch it on when I encounter heavy traffic at highway speeds to aid the stopping power of the coach, if it becomes necessary. Normal interstate exits and intown driving, the brake is off.
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Old 03-17-2008, 05:28 PM   #4
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To add to what Gary said, your exhaust brake or Jake brake as some call it, should only be used when descending long or steep grades is to prevent your brakes from overheating and creating what is called brake fade. When brake fade occurs you will have limited or no braking regardless of how hard you press your brake pedal and lead to a runaway coach. Have you noticed the vehicle run away ramps on the side of highways in the mountains? This is for those that lose their brake ability.
Brake fade can affect any vehicle, cars included, if you ride the brake all the way down a steep hill. This is why you see signs saying to use exhaust brakes or low gear.
I have drove to the top of some Mountains (in my car) and when going back down the Park Rangers have check in stations to check the temperature of your brakes with their laser temperature checker. They will not allow you to continue down the mountain until your brakes are cool enough.
Now, with all that said, you should not leave your exhaust brake on all the time. In some areas I have seen where you could get a ticket for doing so. Some towns have posted signs forbidding the use of exhaust brakes in their area. Depending on the rig, these can be very noisy. It would most likely be a local area noise ordnance violation you would get. The bad thing about local ordinances is that the town can set their own financial penalties. State tickets have almost all the same fine amounts for traffic in the $100 area. Local ordnance fines can be several hundred dollars if this is something that they really dislike and they so choose. Be careful.
Just my observations.
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Old 03-18-2008, 02:55 PM   #5
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<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Now, with all that said, you should not leave your exhaust brake on all the time. In some areas I have seen where you could get a ticket for doing so. </div></BLOCKQUOTE>
Sorry ScubaPro but I do not agree with you. I don't believe there are any places where you can get a ticket for using an exhaust brake.

First,there are fundamentally two different types of engine related braking on diesel engines - compression brake and exhaust brake. Jacobs manufacturing pioneered the compression type brake which physically alters the engine valves and uses the cylinders themselves for braking effect. The so called "Jake Brake", named for Jacobs is of that type. People's concerns with the compression brake are the noise that it produces - the loud chattering that often comes from 18 wheelers. Recently, there have been muffler systems added to the compression brake systems to help quiet this problem. There are some larger diesels in RVs that do have this type of brake system but probably more than 80% of the other diesel powered RVs, including mine, do not.

To add confusion, Jacobs also makes an exhaust brake, along with PacBrake. These units are a nothing but a butterfly valve in the exhaust pipe, closed with air system pressure when activated. They provide back pressure into the engine, helping to provide some braking effect. They are, however, no where near as effective as the compression brakes. Unless the engaging of the exhaust brake also causes a transmission downshift (and therefore higher engine RPMs) they are silent in operation. On I-20 West south of Dallas, I often engage my Jacobs exhaust brake at 65mph and no one but me can tell it is on.

If you will look carefully at the wording on the signs warning of citations for use, they specifically say "engine brake" or "compression brake", not "exhaust brake." I wouldn't hesitate to tell the LEO that my RV was not equipped with an engine capable of violating the ordnance.

To the original poster, some people do leave their exhaust brakes engaged most of the time. I don't. My exhaust brake is activated immediately when I take my foot off the accelerator. For those that require a brake pedal touch to activate the exhaust brake, leaving it on might make sense.
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Old 03-18-2008, 03:32 PM   #6
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Really it is user preference. I choose not to use it unless we are in driving situations that require it, but I am with Chas in that I don't particularly care for how mine is programed. It also comes on as soon as you lift your foot from the throttle.

In past trucks I have driven with Jake brakes (Compression Brakes) have had them programed to come on with an increase in set speed over cruise, or at the first tap of the service brake, in that case I did find I left it on more often.

I do want to stress that it is important to know and understand your equipment's capabilities and limitations. Play with it and see how it works and how effective it is. Use it to suit your needs and make you safer.

With ANY engine retarder type brake assists beware that in slippery conditions (snow, ice or even rain/wet roads) when activated these devices have the potential to create negative torque to your drive wheels, which can reduce traction and cause a skid. With that also remember a skidding wheel will always want to lead, and will also continue in the direction of its original momentum. It is highly recommended not to use Engine Retarders in slippery conditions.

Also to confirm, Chas is correct in that an EXHAUST brake makes very little noise, and you shouldn't have any problem in an "Engine Brake Prohibited" area.

Since your new to diesel's and air brakes, I would also recommend becoming familiar with their operation and proper downhill braking techniques, however I think that is beyond the scope of this thread.

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Old 03-18-2008, 04:04 PM   #7
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I leave my exhaust brake on all the time. I have installed a device (Brake Switch) which only engages the exhaust brake when I put my foot on my brake and when I touch the gas pedal, the exhaust brake disengages. That way, I have it helping me each time I want to stop (don't have to make a motion to turn it on) and not when I just let my foot off of the gas pedal (I coast instead of it engaging).
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Old 03-18-2008, 04:10 PM   #8
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Spartan has recommended NOT leaving your auxiliary brake on all the time, as the service brakes need to heat up to prevent glazing of the front brake shoes.

When applying the service brakes, the rear brakes activate first, followed by the front brakes. The front brakes get the least use and are most susceptible to glazing.

There have been cases where the front brake shoes have glazed, resulting in reduced braking capacity.

This is not covered under warranty, as it is operator caused.

I no longer leave my auxiliary brake on all the time.

At a Spartan seminar, it was asked if anyone had ever replaced their brakes. No one had, so the auxiliary brake was not needed 100% of the time.
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Old 03-19-2008, 08:57 AM   #9
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Nine months and 12,000 miles ago I too was a new diesel Pusher owner. When I first hit the road, I left the engine brake on "low" setting all the time. I quickly learned that this was a PITA because it didn't allow me to "coast". As soon as I would remove my foot from the gas the brake would engage.

I like to be very easy on the service brakes so I now use the engine brake when descending a hill or even when coming to a stop like a freeway off ramp.
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Old 03-19-2008, 09:53 AM   #10
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RickO,
Please take a moment to reconsider using the engine brake as mentioned in your post. Dirk's post is correct on Spartan's recommendation. I have experienced the beginning of brake pad glazing and changed my use of the engine and service brakes.

For those leaving the engine brake on all the time or using it for what is considered normal braking watch out for:
1. when the coach no longer brakes "like it used to"
2. increased peddle pressure is required to obtain "the same braking as before"

means your brakes have started to glaze.

One may be able to save the pads by not using the engine brake unless absolutely necessary. Let the service brakes do their job. They will squeal and stink, for awhile, until the glazing is worn off. If this does not work, it may be time for new pads to return to original service braking performance.
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Old 03-19-2008, 12:14 PM   #11
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Thanks for the advice Gary, but I want to make sure I'm clear on your point.

Are you saying that using the engine brake to slow the coach from highway speeds to off ramp speed and then using the service brakes can damage the brake pads because they don't have a chance to heat up sufficiently and can therefore become glazed?

Thanks again. If this is the case I may have been damaging the pads instead of saving them.
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Old 03-19-2008, 01:38 PM   #12
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Yes Rick, that is correct. In addition to not getting to opperating temperature the pads are not having enough pressure applied to them. This environment is a recipe for glazing of the pads.
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Old 03-19-2008, 01:55 PM   #13
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Thanks much, Gary. Just another case I've discovered where the salesman at the coach dealer didn't know what he was talking about.
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