Engine/Transmission (1998.5 - 2002) Exhaust Brake Questions (long)

[Gene-C]

I have just ordered a Jacobs exhaust brake and not really clear as to how it performs. I know that it blocks the exhaust and causes the engine to help slow the truck.

Does it sense when I let up on the throttle or when I apply the brakes? Does it close all the way are does it come on slowly? If I am descending a hill can I control how much it comes on with the amount of throttle I use?

I have read that some guys are putting a switch on the gear shift. Is this a momentary switch or an on/off switch??? What are the advantages of both???

I guess I need someone to give me Ehaust Brake 101.





Thanks in advance. Gene-C

 

[Thomas]

jakebrake.com



Start downloading and reading.

 

[Sticks]

Originally posted by Gene-C

I have just ordered a Jacobs exhaust brake and not really clear as to how it performs. I know that it blocks the exhaust and causes the engine to help slow the truck.

Does it sense when I let up on the throttle or when I apply the brakes?

If the unit is on, it will block the exhaust when you let up off the throttle

Does it close all the way are does it come on slowly?

It slams shut.

If I am descending a hill can I control how much it comes on with the amount of throttle I use?

As I said above, it slams shut. When descending a hill with or without a load, you can control the ex-brake coming on by the answers below.

I have read that some guys are putting a switch on the gear shift. Is this a momentary switch or an on/off switch??? What are the advantages of both???

The switch on the shifter is typically an on/off switch, this is one way you can control your decent/speed. Some of us are installing a momentary switch on the shifter (see picture below)that will engage the ex-brake at will as long as you want it and as long as the following criteria is met; 1. The throttle switch is not closed (READ, no pressure on the throttle) 2. The unit is on. 3. Jacobs only, cruise control is off (I think that it senses the cruise control) 4. For myself, the clutch switch is also closed.



The advantage to having the additional momentary switch is (for me anyway) my unit did not come with a shifter on/off switch, I did not like the idea of either having the brake on, or pressure on the throttle (slinky driving - speed up, or slow down, no coasting), and sometimes just coasting is enough, especially in city traffic, and unloaded descents on a long hill/pass. A good follow up reason is that I now know that the exhaust is OPEN before I apply pressure to the throttle. There is just a little lag time from the time the throttle switch is activated to the time the brake opens up. I put the switch on the clutch to allow for shifting, thus the exhaust is open when I release the clutch, smoother shifts either up or down. With all this, I still have the option of the brake operating the way it was designed, and can turn it on and leave it on for warm ups, and loaded mountain descents.



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Hurst T-handle shifter with thumb switch. This activates the exhaust brake on command when pushed. Underneath the handle are two switches for reverse lights. One set in the rear below and behind the bumper, the other set underneath the cab pointing just to the outside of the rear tires. On the 4X4 housing, is Scrat, and my US-Gear exhaust brake control box.

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Description: At 2 o'clock off the steering wheel is the switch for the exhaust brake that changes it from normal operation (foot off the throttle and clutch) to on command using the thumb switch on the shifter. At three o'clock off the steering wheel is the standby/off button for the exhaust brake controller.



I hope this helps.

 

[Mundgyver]

I think I can add to what has already been said.



Your Jake system, if you install it as the manufacture directs, will be controlled from pin 20 on the ECM (Engin Control Module). You will wind up pushing a pin into that position from the wire harness side.



Pin 20 supplies 12 vd to the switch when the ECM senses a no demand signal on the throttle.



With the factory switch in the "ON" if you are just driving and take your foot off the throttle, at about 1. 5 seconds the ECM will provide 12 vdc to the Jake which will then close via vacuum from the vacuum control solenoid that comes in the kit.



If you have the cruise engaged and the Jake switch set "ON", the Jake will not engage unless the cruise control disengages. This would mean that you touched the brakes to slow down for some reason or you disable the cruise. But with that said, if you are in cruise condition and the Jake is set to "ON" and you know come to a steep down grade, the cruise will back off. The jake might come on or might not come on. The condition that must be met is for the cruise to fully disengage in trying to automatically slow the truck to control the speed. Once that condition is met, then the Jake will automatically turn on and slow you down. Once you are slowed, the cruise takes over again disabling the jake via pin 20 and keep out at your selected speed.



What I have just described is generally what happens when you are loaded with a bed full of stuff or a trailer on. Its all automatic and the systems work together to hold your speed.



On my truck which is an 01 H. O. with a 6 speed, I have an adjustable needle valve in my vacuum circuit for the cruise to control the response of the cruise to be slower. When I use cruise and turn on the jake, my speed is controled to within 1/2 mph of selected speed no matter what the conditions. I can go up and down hills all day long and never drift more than a 1/4 mph either side of my selected speed.



Hope this help give you a little more insight to what has already been posted previous.

 

[Gene-C]

Follow up question

Thanks for all the information. I have a much better idea how the brake works now.

I received the brake today and reading the install instructions have another question. Where is the ECM connector located?? The picture they furnished is very poor. All other instructions are pretty good.



Thanks again. Gene-C

 

[Mundgyver]

Ohhhhhhh boy, are you in for some fun It is a pain to get too. Open the hood and take a good look at the fuel filter. Look under and behind it just forward of the lift pump.



It's a pain to get too. I wound up going after from under the truck. There is a bolt in the center of it that hold it in place.



Make sure you double check and triple check the pin position before you drive the pin and wire into the hole. Once it is in, most people will not be able to get it out. You need a special tool to unlock the pin for removal. Just go slow and double check which hole you are putting it in.



The rocker switch will be kinda of fun and you might want to think about putting it in another location beside below the power receptical. Its ok there, but you can't hardly see the light when it come on.



I could do one in about 2 hours now. Took me about 4 and 1/2 the first time because I was taking my time routing everything.



Good luck. Oh yea, if you have not done so already, get yourself a set of factory manuals for the truck. They will be the best investment for base knowledge.

 

[Mundgyver]

sticks,



Question, you have a red faced electrical box of some type down by the 4XShifter.



What is that thing please

 

[Mad Bomber]

Ex brake

The worst thing about a ex brake is they work too good going down a hill and you have to turn it off.

 

[MMiller]

To bad there isn't a way to have a couple different steps to the exhaust brake like a engine brake on a big truck. You can select 2 cylinders to jake on, or four or all six. It would be handy if the valve could be set up to mabe go 1/3 shut then maybe 2/3 and then all the way, for varying loads,condtions.



Or maybe this is possible? Surely sombody has tried to do this.



Michael

 

[Sticks]

Originally posted by Mundgyver

sticks,



Question, you have a red faced electrical box of some type down by the 4XShifter.



What is that thing please

That is the early model (1995 ish) US-Gear main control box for their brake. It has a on-off switch, but when on, you still have to push the wireless remote button (red square just off the steering wheel on the dash) to put the system on standby... . OVERKILL, and when the battery dies in the wireless I AM SCREWED and have to spend the $$$ on a new updated control box.

 

[jrandol]

A local Case dealer mechanic says he saw a company that made true jake brakes for our trucks. He was going to try and find the catalog with the companies name and info for me. has anyone heard of this?

 

[Sticks]

Originally posted by MMiller

To bad there isn't a way to have a couple different steps to the exhaust brake like a engine brake on a big truck. You can select 2 cylinders to jake on, or four or all six. It would be handy if the valve could be set up to mabe go 1/3 shut then maybe 2/3 and then all the way, for varying loads,condtions.



Or maybe this is possible? Surely sombody has tried to do this.



Michael

I don't know that there would be an effective difference at 1/3 or even 2/3. That would be like switching from a 4" exhaust system to a 2. 66" (1/3) then a 1. 33" (2/3). Maybe an electrically adjustable "wastegate" on the exhaust, pre brake, that would have different psi open points.



TOO MUCH DAIN BRAMMAGE

 

[Boondocker]

ECM access tip

2 bolts hold the fuel filter bracket to the top of the engine. Remove these 2 bolts, do not disconnect any fuel or electrical lines. This just provides a little slack so you can reach the ECM from the top. Be careful not to stress any fuel filter related lines. Reinstall the bolts and tighten the bracket when done.



Neil

P. S. This works on my 2002.

 

[benhall]

I like the idea of an engine brake on my truck. The only bad thing is that we have such a tight fit between the valve cover and the cowl as it sits right now.



Ben

 

[Gene-C]

Its In Almost!!!!!

The Exhaust brake is in almost!!!!!! You guessed it. All except the ECM wire. Thinking about removing the fender well lining to get better access. It is held with those plastic button things and shouldn't be to bad to replace. Has anyone done this?????



I got a two speed axle switch from NAPA and mounted on the shifter. Very easy to turn on and off. Heat shrink the wires and run through the boot and up under the dash out of site. Neat Job.



It will be a couple of days till I can get back to finish it. I'll post when the job is done and let everyone know if the wheel well access worked out.



Gene-C

 

[Sticks]

Oo. Oo.

 

[Mundgyver]

In looking at where you are located and I know you have to have some snow or ice, a word of caution when you go to test it.



Be very careful if you use it on snow or ice. I think the book says it is not recommended. You can find your self in a world of spin on slick surfaces because it does have the ability to cause the wheels to slide in those conditions.



Dry pavement is what you want to use this on.



Have fun and enjoy it. I am at 107,000 turns with my original brakes. I still have about 50% left.

 

[Gene-C]

The Jake is in and works great. Oo. I un bolted the intake at the grid heater and slid it out of the way. I didn't have to remove the wires to the heater. I then removed the two bolts holding the fuel filter and moved it out of the way. I did not remove the fuel lines. Bingo!!! there was the ECM plug and very easy to get to now. Punched out the sealing plug on #20 and inserted the wire.

Everything went back together without a hitch.

Thanks all for the helpful advice. It made the job a lot easier.

 

[Mundgyver]

Glad it went smooth for you. When you get you first heavy load on the truck, is the time that you will be thanking yourself for make the investment.



Enjoy

 

[Sticks]

Originally posted by Mundgyver

In looking at where you are located and I know you have to have some snow or ice, a word of caution when you go to test it.



Be very careful if you use it on snow or ice. I think the book says it is not recommended. You can find your self in a world of spin on slick surfaces because it does have the ability to cause the wheels to slide in those conditions.



Dry pavement is what you want to use this on.



Have fun and enjoy it. I am at 107,000 turns with my original brakes. I still have about 50% left.

I have used mine on the snow/ice. 2wd is a little spooky, buy not catastrophic. 4wd was like the roads were dry. Funny to watch other people slide through the intersections with the brakes locked up as I gear down and stop like the roads were perfect.