enafzige

Quick question...

After the install of the Helix 2 camshaft, the Jacobs exhaust brake no longer has any braking power at all. Is this the result of the camswap? I've read hours upon hours of material before purchasing the cam, and don't remember anything being discussed regarding exhaust brakes.

I've checked the electrical connections, verified vacuum to the pod, and verified the linkage was working on the elbow. I even removed the exhaust right past the elbow so I could see the butterfly valve closing and opening as the brake was applied...and everything appears to be operational.

However, since the camswap, you can't even hear the exhaust brake come on at all. It provides absolutely no braking power. Prior to the camswap, I could be driving at 60 mph in 5th, and down shift to 4th so quick that the exhaust brake kicking would cause the 37" tires to chirp!

Thoughts?

--Eric

Don M

That sounds strange. The exhaust event is earlier on the H2 VS the stock cam, but it is not earlier than the older engines already had. The 12 valve and earlier 24 valve VP44 engine had earlier opening exhaust valve events than the current CR engines and their brakes worked fine.

You now have zero braking? That sounds like some thing else is goofy.

metal_miner

I remember a while back DTR member ABC4yew posting a thread about the exhaust brake working so well with his twins and Helix cam that it was terrorizing his valve seals! He tows real heavy too.

ratsun

I think theres a problem with your brake.
I know my BD brake worked as well after my H2 swap as it did prior?

TriSum

This just happened to me. When I had my engine installed, (with Helix cam), the mechanic cracked the pressure regulator for the brake and it wouldn't work at all. Swapped the regulator and whala, exhaust brake.

Check it out.

David

AH64ID

subscribing.. I want a H2 but not at the cost of my EB.

enafzige

Hmmm... What is the pressure regulator? Do you have a part number for this?

Thanks for the comments. I'll give it another look.

--Eric

TriSum

The pressure regulator controls the pressure of the air coming from the pump/tank up to the exhaust brake.

Too little pressure and the brake will not engage. In my case the regulator was cracked not allowing pressure to build up and engage the EB.

To find it either follow the air line from the EB back to the regulator or follow the air line from the pump/tank forward up to the EB. It will be somewhere in between the two.

David

AH64ID

He has a jacobs brake.. no regulator.

TriSum

Oops!!

Sorry, can't help you with that one. Good Luck !!

David

enafzige

Yeah, I'm not sure what's going on. I guess I need to more carefully inspect the lines and make sure there's no leaks.

Does anyone know what vacuum the Jacobs pump should be making? I can put a temp gauge on there to check if I have the spec.

All in all, this is a pretty simple system, so it's confusing me what could be wrong.

The pump is making good vacuum, at least by feeling it with my finger. The vacuum solenoid and in-cab switch are working...no vacuum on the outlet side with switch off...vacuum on outlet side when switched on.

I removed the inner fender well to inspect the linkage from the vacuum pod to the exhaust elbow. When the exhaust brake is engaged, the rod visibly moves the full extent of travel.

I also disconnected the exhaust right after the brake, and observed the butterfly flapper opening and shutting.

I'm kindof stumped right now. Is there anything concerning the cam/injector/valve spring install that may not be right? Truck runs great with no unusual sounds.

When the brake is engaged, there is very little audible change, either in the exhaust or engine sound. With the brake engaged, there is a little less vacuum on the intake side.

The only thing I can think of right now, is that the butterfly may be warped and not fully seating???



--Eric

xtoyz17

My guess is you're not pulling as much vacuum as needed. The reason you can see this at idle is because it will require little effort to move the butterfly. If the engine is spinning faster, greater load, etc... you probably don't have enough vacuum to close the butterfly.

Just a shot in the dark there, as I know nothing about the Jacobs system...

Shawn

Utundra

The vacuum pump should pull 15 to 29 inches of Mercury, this is from the Jacobs Troubleshooting section of the installation manual.

All of the manuals can be found here, http://www.jakebrake.com/support/par...obs_product=42

Hope it helps, good luck...