Jacobs exhaust brake hissing:o)

[Boondocker]

I recently installed a Jacobs exhaust brake. Haven't towed with it yet, but as far as I can tell, it works. However, it makes a loud hissing sound when activitated, the hiss is louder than the exhaust. I've checked the bolts on boths sides of the exhaust elbow, they're tight. I've checked for exhaust and vacuum leaks and can't detect any. I can't tell exactly where the sound is coming from, but the actuator seems most likely.



Maybe this is normal and nothing to worry about, but I have no previous experience.



Troubleshooting tips or reassurances appreciated.



Thanks,

Neil.



P. S. scares pedestrians

 

[Stranger]

Normal

Sounds normal to me. Actually it makes it sound sort of like an Abrahms Tank.

 

[JWhitcomb]

Hissing is normal, gas has to go somewhere.

 

[Casey Balvert]

Normal. Exhaust gasses are being forced through a small hole in the brake butterfly when it is activated.



Casey

 

[Boondocker]

it's just the normal noises in here

That's a line from a Tom Petty song.



So far it's unanimous that the hissing is normal. Thanks for the reassurances. I don't mind if pedestrians and other motorists think something is wrong with my truck as long as I know otherwise.



Neil

 

[JWhitcomb]

Just install a switch on your gear shift lever so you can shut the brake off with ease.

 

[Boondocker]

shifter switch is a must

Wouldn't have it any other way.



I bought the Cummins shifter-mounted switch for the Jacobs 2003 ISB model brake (a bit spendy even from the Cummins dealer).



Unfortunately it's not a direct replacement for the 98. 5-2002 supplied rocker switch. The wiring harness from the brake is a 4-wire and the shifter switch is a 3-wire. The outcome is that the switch activates the solenoid just fine and connects to the ECM pin-20 for the 1-2 second delay. The only problem is that the red LED on the switch doesn't light. The light isn't necessary, but it's not perfect.



Since I bought the switch as a separate part (not in the brake kit), there are no instructions for it. I posted this dilemma on the 3rd-Gen. forum looking for someone who has installed this switch and may have instructions from the 2003 kit. Got lots of reads but no responses.

I think I'm supposed to win a prize or something if I stump the panel.



Neil

 

[DHawthorne]

It works real good in my rig. Holds a 8% grade in 5th gear with no problems and no brakes. I wanted the manual shift mounted

activator as well. Did not know were to get it. I think its a little slow sometimes when in traffic. The book says if you turn it on on cold mornings it acts like a EGR valve and warms the engine up faster at idle.



Enjoy it.



Dave

 

[CFAR]

Hissing is perfectly normal, you are not the only one to look for the leak. I think everyone whoever put one of these in has done the same.



Bob V's super shifter.