Engine/Transmission (1998.5 - 2002) Vaccum and Exhaust brake performance

[IWeiny]

So we went out again last weekend. I was noticing that my Exhaust brake did not seem to retard as much as I remember. Now I can attribute this to 3 things.



1) I have just gotten used to the brake, ie it is all in my mind.



2) I have a vaccum leak caused by my fiddling under then hood, probably knocked something loose.



3) Brake is not working right.



I don't think there is anything wrong with the brake as I put a back pressure guage in and I am getting back pressure. But it does not seem to be as high. The guage is not really accurate. It reads about 12. 5 # at Idle. I thought the manual said for the 24V I could go up to 15-20# at Idle. But I don't know how to adjust this.



So 2 questions:



1) what back pressure should I have at idle, and how do I adjust it.



2) what is good vaccum for the system?





PS the load did not change substantialy, in fact I have removed a bunch of stuff off my trailer to the tune of 200-300#.



Thanks,

 

[y-knot]

I run a vacuum Gage just to keep an eye on things like this, there are many systems that depend on vacuum. Like the CAD in a four wheel drive, the cruise control, HVAC system and of coarse your exhaust brake. A good working vacuum system should be in the 20-25 inhg, mine holds a steady 25. Of all the things we tend to monitor, few are as important as the vacuum, of which less then 1% see fit to observe it's standing.

 

[IWeiny]

Thanks for the reply

I am headed home now and will check vaccum.



Thanks again,

 

[Midnite]

Originally posted by y-knot

Of all the things we tend to monitor, few are as important as the vacuum, of which less then 1% see fit to observe it's standing.

I don't know if I'd go that far. I wouldn't mind having a vacuum gauge in my truck, but I sure wouldn't consider it more important than fuel pressure, boost, or EGT. If my cruise control craps out, or my 4wd doesn't engage, it's irritating. However, if my fuel pressure drops to single digits, or my EGT hits 1500 degrees, I actually have real problems.



Mike

 

[jelag]

For your exhaust brake to work you do need the 23-25" of vacuum... . if your exhaust brake has a test port in front of the valve you can test the back pressure... The max back pressure at 2300 rpms should be close to 60 psi.....



We often find the power brake booster leaking. . and the pump can't keep up... . We usually end up pulling or plugging lines. . and sometimes find bad pumps... .



We take the pac brakes out and test drive them with the gauge installed... . run the engine up to 40 mph and put the transmisson down into 3rd as I remember and let the rpm go to 2500 and turn on the brake.....



Hope this has been some help...



Jim

 

[IWeiny]

Yes that helps.

I checked the vaccum last night. 28" with and without the brake on... :-(



I know I don't get anywhere near 60# of back pressure at any RPM. I think 30# is the most.



So now I guess I need to adjust the brake?



Thanks,