2nd Gen Non-Engine/Transmission Sticky Jacobs Exhaust Brake

[Elk_aholic]

Any Ideas?



I have a Jacobs exhaust brake that seems to have a mind of it's own :-{}



The brake works as advertised when descending a steep hill loaded or empty, but at slower speeds and when starting out from a stop light, the brake does not want to deactivate as throttle pressure is applied or shifter mounted rocker switch is turned off. It eventually deactivates but sometimes takes up to 10 seconds to do so. This can make for a harry situation when trying to merge into fast moving traffic from a stand still. I can't believe this is a good thing for the engine especially after observing the black smoke being expelled from the tailpipe when this happens??



Thanks in advance for any possible solutions you may be able to provide.

 

[JL penner]

Could be a couple of different things. The solenoid could be sticking open (not likely, but possible), or the intake side of that canister could be clogged up.

 

[JL penner]

did you ever figure this out?

 

[Andy Redmond]

Is it a 12 or 24 valve?



If 12 v also ck. the micro switch adjustment.



If 24 v. it might also be fritzing out at the pin 29 of the ecm? that give the solenoid a signal to complete the circuit.



Maybe the solenoid is draggy or you have a good vacuum leak?



Do you have a mighty vac or other hand vacuum pump? If so, see if the can is sticky at the brake casting or to test for vacuum leaks in the vacuum piping.



Good luck and let us know what you found



Andy

 

[Elk_aholic]

Thanks for the responses. I have not had the time to check some of these possible solutions out. I was wondering if the butterfly valve could potentially be warped? It seems I have read somewhere that this has happened to other brands of brakes? The odd part of this whole thing is, is that if I start the truck in the driveway and activate the switch, it turns off and on like it should. After driving the truck for a while and then trying this same test, at idle, the brake will come on but will not disengage like it should?? If the problem were electrical or vacuum related, wouldn't it act eratic all the time??



I must apologize. This was my first post and I thought my vehicle profile would automatically show up since I had filled it out. I guess I have to list this info as my signature?? I'll try this.

 

[CJ Lagos]

Be careful when the brake engages and you are trying to accelerate. The lack of boost will cause the EGTs to skyrocket and it is very easy to see 1300+.



If the problem is with disengagement, I would check the microswitch, actuator and selenoid. I would check the vent line off the actuator because this is where the vacum goes when the brake releases. You can test the actuator with a mightyvac and the microswitch with a multimeter.



Another helpful test would be to disconnect the two leads on the selenoid, put one to ground and one to 12v. Cycle the brake a couple times and observe what is happening.



If you suspect the butterfly valve itself, disconnect the actuator and open and close the valve by hand to confirm.

 

[Elk_aholic]

Well I think I fixed the brake. I removed the brake from the truck and gave it a good cleaning with "Deep Creep" solvent. I figured it wouldn't hurt and if it was still acting up, I would test for proper vacuum pressures and electrical connections. Seeing as how the brake would activate ok, and just not deactivate, I thought it must be a dirt/carbon issue or a warped butterfly valve. Having the brake in hand and pushing on the actuator rod, you would think there would be no way the brake could stick on, with the amount of spring pressure used to release it! I reinstalled the brake and now it deactivates with the slightest throttle pressure and/or by flipping the swith to off. Time will tell if this was a true fix??



Cheerio

 

[Oly]

Hey,



You should disassemble the solenoid. After a while the plunger and seals get dry and or dirty. A jewelers screwdriver and some Q-tips, and carb cleaner will do it. I used WD-40 to lubricate the o-rings. Done this twice and after 100,00+, still works like a champ.