Community Forums

dennis45 · 08-10-2019, 04:08 PM

Quote:

Originally Posted by jcussen

Curious why the the egt's and water temps will rise. Unless your coach is very different than others, exhaust brake will not activate if you have any throttle on. So with practically no fuel being burnt, what causes the egt and water temps to rise?
Have used exhaust brake on many long grades, and have never seen this.

I think it must be like when you pull the logs off the campfire it gets hotter. Oh, wait a minute, it's the other way around.

BTW, the exhaust brake is not activated at all until you remove your earth pad from the pedal.
My guess is going up the mountain your earth pad would be anything But Off the throttle.

jcussen · 08-10-2019, 04:26 PM

Quote:

Originally Posted by dennis45

I think it must be like when you pull the logs off the campfire it gets hotter. Oh, wait a minute, it's the other way around.

BTW, the exhaust brake is not activated at all until you remove your earth pad from the pedal.
My guess is going up the mountain your earth pad would be anything But Off the throttle.

Pretty well what I said, "exhaust brake will not activate if any throttle on". Was responding with question on why exhaust brake will heat up engine going down hill, just like engine load does going up hill? Any ideas?

dennis45 · 08-10-2019, 04:52 PM

Quote:

Originally Posted by jcussen

Pretty well what I said, "exhaust brake will not activate if any throttle on". Was responding with question on why exhaust brake will heat up engine going down hill, just like engine load does going up hill? Any ideas?

Sorry, my comment was not directed toward you. It was for the post you answered.......I'm on your side.

Domo · 08-10-2019, 05:50 PM

Quote:

Originally Posted by Cousin Ed

If you engine brake is on all the time, your service brakes will not get enough use and they need to be used.

I do not understand this, sorry.

I've read a previous thread where someone was extolling how a savvy driver's service brakes could last exceptionally long times by using the exhaust break judiciously; "as if new." That thread never mentioned anything negative about not using the service brakes.

For myself, I use the exhaust but, when slowing the last few hundred feet to a stop/intersection/etc. I use the service brakes <-- wouldn't that be enough to keep them from rusting/freezing/locking/getting bored?

I always learn from reading the forum and welcome any input and correction to my "normal" routines.

jcussen · 08-10-2019, 06:08 PM

Quote:

Originally Posted by Domo

I do not understand this, sorry.

I've read a previous thread where someone was extolling how a savvy driver's service brakes could last exceptionally long times by using the exhaust break judiciously; "as if new." That thread never mentioned anything negative about not using the service brakes.

For myself, I use the exhaust but, when slowing the last few hundred feet to a stop/intersection/etc. I use the service brakes <-- wouldn't that be enough to keep them from rusting/freezing/locking/getting bored?

I always learn from reading the forum and welcome any input and correction to my "normal" routines.

Agree, poster must have a super exhaust brake, mine would slow me down, but in most situations, I would have to use service brakes to come to a complete stop, unless I started slowing down a long long way beforehand.

retiredusps6 · 08-10-2019, 06:35 PM

Your brakes move to the drums when use the parking brake assuming you have air brakes so that kills the idea your brakes will freeze up.I Drove many a truck with exhaust and Jake brakes. I always ran with them on rain sleet snow. Jake brakes will lock up the drive wheels.Exhaust should be used often to keep the linkage and carbon build up down.On mechanical motors you use to be able to select high or low.
Old Cummins Mech you had to turn off or it would kill the motor. Electronic motors the computer will turn it off at a preset RPM.

Cloud Dancer · 08-10-2019, 06:58 PM

On the open road I run with it OFF. If I experience a tire blowout I want to first JUST keep steering without any interference by anything other than the blown tire, and the shaking.

A Traveler · 08-10-2019, 07:14 PM

I am always amazed at how much just plain wrong information is out there about this subject. Wow.

First...yes your coach can be programmed so the engine brake acts differently. Freightliner programs the brake to downshift to the next lower gear as soon as it can without over-revving the engine in the next lower gear. In other words, they set it to deliver absolute maximum engine braking every time you use it. Why do they do this? Because they assume that you don’t really know how to use an engine brake, so they program it for 100% braking 100% of the time. (A Freightliner exec told me this.) The transmission will target 2nd gear and shift down as soon as it can in each gear until it gets there.

What if you don’t want maximum engine braking? I had Allison reprogram my transmission so it does NOT shift down when the Jake Brake engages. It was the best mod I ever made to my coach. Slowing for an interstate off ramp, coming down a gentle grade, driving in traffic, these are all scenarios where I can now use the Jake brake without getting thrown into the windshield every time the transmission shifts down. If I need maximum braking, a few taps on the down arrow on the transmission controller and I’m there. It took 30 minutes and about $45 at my local Allison shop to get this done.

I now run with the Jake brake on high 99% of the time. However, if you are the type of driver who just puts it in ”D” and drives without getting actively involved in your driving, then this mod is probably not for you.

As for an exhaust or compression brake INCREASING engine temps, that’s a new one...and totally incorrect. There is no fuel at all being burned in the engine when your foot is off the accelerator. Zero fuel. Zip. Nada. None. Without the heat of combustion, the slight increase in back pressure with an exhaust brake will not cause any increase in engine temps. The same holds true for a Jake (compression) brake. All the energy of compressing the air is released when the exhaust valve opens at the top of the compression stroke. Much of the heat generated in the compression stroke is released as well. And again...there is zero fuel being burned in the cylinder under these conditions!

ScoobyDoo · 08-11-2019, 07:55 AM

Not RV, but once at a roadside safety inspection I was told my tractor brakes must not be working because rust in drum. "Can you give me 10 seconds before you write?" Stuck it in low, stepped foot valve for a few feet. LEO said "They work fine, why...?" That's a company trailer. They have more money than I. If I'm driving right, the jake and trailer brakes will stop me.

Dippytwo · 08-11-2019, 01:23 PM

I know I’m still ignorant about DP’s because we haven’t had ours long and haven’t driven it much yet, but I have seen on this and other post that you shouldn’t use the engine brake when the roads are wet or when raining. Why? I would have thought the engine brake would be safer then risking locking up the manual brakes.

I can see why maybe I should turn them off when on the highway when it’s flat and not much traffic so the brake doesn’t engage any time I let my foot off the gas.

Dippytwo · 08-11-2019, 01:47 PM

Quote:

Originally Posted by Dippytwo

I know I’m still ignorant about DP’s because we haven’t had ours long and haven’t driven it much yet, but I have seen on this and other post that you shouldn’t use the engine brake when the roads are wet or when raining. Why? I would have thought the engine brake would be safer then risking locking up the manual brakes.

Just to be clear, my toggle switch for the brake says “retarder” which I guess is a exhaust brake. I’m not sure if that’s different then a engine brake or not or if the answer to my question will change or not.

Crasher · 08-11-2019, 02:26 PM

Quote:

Originally Posted by Dippytwo

I know I’m still ignorant about DP’s because we haven’t had ours long and haven’t driven it much yet, but I have seen on this and other post that you shouldn’t use the engine brake when the roads are wet or when raining. Why? I would have thought the engine brake would be safer then risking locking up the manual brakes.

I can see why maybe I should turn them off when on the highway when it’s flat and not much traffic so the brake doesn’t engage any time I let my foot off the gas.

It's not so much the exhaust brake that can get you into trouble on a wet surface, but the combination of the EB coming on and causing the transmission to downshift and lose traction. I had it happen @ 35 mph on a rain slick road at a slight curve. When our 36' DP suddenly downshifted, the rear wheels broke traction and we found ourselves sliding broadside in the middle of the road. Only when I added power, did the rear wheels gain traction and I gained control. It was a rare event, but convinced me to turn it off on slippery roads. An engine compression brake is far more aggressive than the exhaust brake.

jcussen · 08-11-2019, 08:12 PM

As crasher says, plus most newer coaches have ABS on all wheels, preventing lockup and possible loss of control. I leave my retarder on all the time in dry weather as it only activates in combination with my brakes. Wet weather no.
A retarder is a different concept than an exhaust brake, but results are similar to exhaust and compression brakes except it acts on transmission instead of engine.

lawjohnson · 08-11-2019, 08:24 PM

I leave mine on around town and in the mountains, it is off the rest of the time. I don't know about anyone else but my cruise control does not engage with it on.
Also, I just had to replace my track bar due to the bushings being worn out. The advisor at the shop told me it was more than likely due to the exhaust brake being on all the time and the trans constantly up and down shifting by the previous owner who did tell me he never turned it off. 56K on the coach. BS?? I don't know but the bushings were most definitely shot I do know that.