Mandatory Idle-Jacobs brake or fast idle

[CROW]

My truck is a 2003 HO 6 speed with the Jacobs exhaust brake. I use it to tow a fifth wheel. Even though I know better, we just got a new puppy and now I have a dilemma concerning idling. There will be times (such as when we stop to eat) when the dog must remain in the truck and the truck will need to remain running to provide cooling or heating for the dog.

1. In hot weather, would I be better off to turn the Jacobs brake on and let it idle at the normal idle speed or use a fast idler such as the one on page 8 of the latest Geno's catolog and run it at 1,000 or so RPM?

2. Same question, but in cold weather?

3. Has anyone used the fast idler mentioned above; does it work OK or does the engine tend to vary a lot in rpm due to the AC compressor going on and off.

Thanks in advance for your responses.

 

[jelag]

Find the 12V power connection to your exhaust brake..... and install a switch to turn on/off your brake..... It wouldn't hurt to let it run with the exhaust brake... but the truck makes a funny sound... .



Even though Cummins suggest that you not long idle your engine... . once it broken in I see no reason why you can't do this... you'll notice a lot of them doing that in truck stops... . execpt in CAL, as of some date, you can't idle a truck longer than 5 min... It's now against the law.....



Anyway... I usually start mine in the morning and when I walk away from it... I take the remote opener and let it idle when the outside temp is above 90 or below freezing... I do it for my own comfort... ...



Hope this helps... .



BTW - the computer will adjust idle when the A/C compressor starts...



Jim

 

[Radshooter]

Silly newbie question, but what difference does it make during extended idle if the exhaust brake is on or off? I sometimes let my truck idle too while I am in the grocery store for a loaf of bread. I never idle with the exhaust brake on. Should I be????



Thanks

Steve

 

[Gypsyman]

With the Jacobs, even if the switch is in the on position the brake will only cycle on if the engine temp is to low or if the vehicle is moving. It's all automatic...

 

[Vaughn MacKenzie]

You can idle all day long and do no harm at all in hot weather. I would not idle up, and definitely do not use the exhaust brake. You're generating plenty of heat underhood as it is running the AC, so why add to the heat load. You're in no danger whatsoever of combustion temps dropping below 140F (point at which it becomes a concern).



Vaughn

 

[WPeschel]

What about so called "cylinder wash"???? From prolonged idle time... .

 

[PatrickCampbell]

I have umpteen engine hours on my truck. Here is what I did, I stuck a stick between the seat frame and the throttle to go anywhere from 1000 to 1200 RPM. This is kind of annoying and a button would be a lot cooler, but costs more money.



In hot weather if you leave the A/C on the truck will stay up to temperature but in cold weather, it definitely will not. Putting the A/C on will help it stay up to temp. a little bit by putting a load on the motor in hot or cold.



I had a Lund brand cold front that I put over the radiator grille in really cold weather and then rev'd to around 1200 RPM to keep it up to temp.



I think cylinder washdown only occurs if the motor is not up to temperature? I. e. idling when cold for long amounts of time??? or does it have to do with engine rpm?



BTW if enabling the jake brake wouldnt hurt anything, why not do it... ?

 

[klenger]

On the new trucks (not sure when it started), the EOM exhaust brake is automatically turned off when the speed is zero and the engine is warmed up.

 

[RustyJC]

For my 2G 24V truck, I idle it with the Jacobs e-brake on if it's going to be idling for extended periods. This puts some load on the engine, increases EGT to about 450 degF and helps prevent the varnishing of the valve stems/guides caused by low EGTs that can lead to bent pushrods (or push tubes, as Cummins calls them). There's a Cummins advisory out on this for 2G 24V trucks - see especially items 3 & 4. It's a nice feature, as it also warms the truck up faster when I'm hitching up the 5th wheel.



Rusty

 

[Vaughn MacKenzie]

I think cylinder washdown only occurs if the motor is not up to temperature? I. e. idling when cold for long amounts of time???

Yeah that's what I was referring to when I mentioned 140F is the point of concern, meaning EGTs of 140F or lower is when washdown and deposits start to be a problem.

 

[RustyJC]

Yeah that's what I was referring to when I mentioned 140F is the point of concern, meaning EGTs of 140F or lower is when washdown and deposits start to be a problem.

Vaughn,



Don't you mean coolant temperatures of 140 degF or lower?



Rusty

 

[CROW]

Thanks for the responses. The information that came with my Jacobs exhaust brake indicates that the ECM will turn the brake off at idle when coolant temperature reaches 170-175 degrees. It appears as though there would be no possibility of overheating the engine in hot weather with the exhaust brake on at idle since (absent a malfunction) the brake would turn off and the engine would cool down. My though on leaving the exhaust brake on at idle in hot weather was to keep the engine temperature up to a "safe" level since the cooling systems on these trucks are so large and efficient. Guess if it is hot-say 90 degrees-you don't have to generate much heat to get engine temperature up to at least 140 degrees and avoid the cylinder washdown issue. See all the problems a dog will create.

 

[PatrickCampbell]

If we are talking about engine coolant temperature, in hot weather with the A/C on, your needle will never go LESS than slightly LEFT of the middle mark , no where near 140 F.



If you turn on the exhaust brake and it gets too hot, it'll shut off supposedly... but it won't go BACK on if it gets below 170-175 F right? I think cold weather is more important to worry about in which case you might want to still idle up a bit even with the exhaust brake on. Keeps oil pressure up too. The stick thing is a little "ghetto" but works.