Engine/Transmission (1994 - 1998) engine brake problems

[GMcLean]

Got a 97 1 ton with a jacobs engine brake which still turns one(butterfly valve moves fully over), but does not have any hold back power. I can hear the engine trying to labour and it does change tone slightly, but it just simply isn`t working properly. Do I need to change to 60lb exhaust springs or do I have other problems?? Thanx in advance. . Garth

 

[WDaniels]

If I'm correct, the Jacobs exhaust brake is actuated by an air compressor. Do you have any air leaks?

WD

 

[Kalaehina]

I always thought the kit came with the 60lb springs? Not really sure though.

 

[Whitmore]

I have installed 3 Jacobs brakes now, all of them were on the newer models , the brake has a solinoid that activates the butterfly valve, the solinoid operates from the truck vacumn system.



I can think of 2 possible problems you may have .



1- I think its prolly gonna need the 60 # valve springs ?



2- Your actuator may be gummed up ? I would get the truck at an idle with the Jake on and then check to see if it is turned 90 * from its starting point, you may get some help from a person in the cab so you can watch the actuator work.



cheers, Kevin

 

[Steve Campbell]

I think Whitmore is...

... on to something. Taking it completely off of the engine, if his test proves positive, and cleaning it up to show room clean will probably solve your problem



I do not know what kind of lube is compatible with the vacuum system on these trucks. The vacuum cannister will need some kind of cleaning/lubing.

 

[BWilson]

Whan my Pacbrake began wworking slowly (or not at all) it turned out to be a lot of gumming (looked like water residue) in the vacuum cylinder. However, mine would either come on and stay on (where you definitely can tell) or not come on at all.



How do the Jacobs brakes valve? I know the Pacbrake uses a hole in the butterfly (two holes if you don't have the 60# springs) and the BD brake uses and internal valving in the piston. To me it sounds as if it is internally valved in the piston and it's gummed up. I would think you could pull cylinder and disassemble it and clean it without pulling the entire brake off.

 

[Whitmore]

I know the Jacobs brake is a fail open valve, as far as I know its the only one on the market that fails open ? When I was looking at brakes I think I remember that the BD and Pack fail closed, this will leave you stranded in the event of failure because then the truck willnot go past idle, anyone enlighten us on this ???



cheers, Kevin

 

[Bob V]

The Pac-Brake and the B-D use a double acting cylinder to operate the brake, vacuum opens and closes the butterfly. Jacobs uses a single acting cylinder, vacuum closes the butterfly and a spring opens it. It is possible that you cold have a vacuum leak that won't allow the butterfly to close completely when under load.

Bob V

 

[GMcLean]

I did watch the valve the other day while it was actuated on and off, and it did look like it was moving through the full motion of the cyl and when it was fully closed, I pushed it down with a hammer handle. It did not sound any different than it did before, but the cust said that it did work better after he left!!??? Sounds like you guys who were for the gumming up vac cyl may have just stumbled onto it. . At an idle, we cannot hear the brake like I feel we should, ever since I put the 3 peice ATS exh manifold on it. . His OEM manifold would shrink and snap off exh manifold bolts and then he had a major exh leak and could really hear when the brake came "on". Possible when we changed the manifold and had to remove the jake that something shifted and caused the brake not to work. . I will remove the jake and try to clean it. . Thanx for all the great input guys. . Garth