97 American Eagle Pacbrake issue

[gene409]

I have been living with a 1997 for a few years without the use of the pacbrake. We live in Colorado and we havent been west over the mountains since. The issue started coming down a hill as i flipped the switch for the brake the coach began to slow. Once close to the base of the incline i switched it off but nothing happened. The engine had lost most of its power and we could only run maybe 15-20mph max ( i suspected a gate or door stuck closed). As i tried to get to the next town we slowly started to pick up speed and after about 10 miles we were full speed ahead. The brake now does nothing when turned on. I suspect something stuck (not to mentioned I'm spooked about trying it).

Heres how stupid i am. I cant even find the unit! I see the exhaust manifold, the turbo, a large 3 inch intake leading in from the air cleaner and the exhaust pipe leading under headed to what must be the muffler. Does this coach use an exhaust unit or is it built into the head as an actual engine brake? 8.3 325hp cummins power plant. I have spoke to several MH repair businesses and this is an area no one so far seems to know anything about other than it might cost thousands to fix!

Im not new to mechanical stuff after racing USAC midgets for years building my own cars, motors etc and today enjoy 60 muscle cars. Can someone help a dumb kid out.

My wife and i went and looked at new coaches the other day and after hearing what they would offer on trade in I decided they could bury me in the thing when the time comes. Sorry for the length.

[BigSkyBob]

Your exhaust brake should be located at the turbo discharge. There is an air cylinder that activates the butterfly gate that closes off the exhaust flow. It should be obvious as it's a large cylinder with an air hose attached.

[Sammie]

This is what it should look like.

http://www.pacbrake.com/files/images/hi_res/PRXB_2.jpg

[gene409]

Im going to post a photo tomorrow and maybe i am overlooking the obvious. Thanks for your input. I will be back tomorrow.

[rmmpe]

The photo shown is of a Pac Brake PRXB model, which is newer than what was stock on a 1997 engine. If yours is the stock unit, it will look similar but without the large external spring and lever.

Regardless, I believe most, if not all, exhaust brakes are installed immediately downstream of the Turbo.

When you find it, use a large adjustable wrench or pipe pliers to actuate the lever the cylinder’s rod-end is attached to. If you cannot make it move, the butterfly valve’s shaft could be rusted stationary. If so, squirt some PB Blaster on the shaft and let it penetrate for a day. Then try to move it again. If you can get it to move, lubricate the butterfly shaft thoroughly with Pac Brake's lubricant (which should be done at least once per season - more often is better). If you still can't get it to move it may be the cylinder, which is sealed and not repairable (but obtainable from Pac Brake).

NOTE:
If you decide to/must remove/replace the entire assembly, you might be better off to replace it with the newer PRXB model, which provides superior braking in the lower RPM range (about $700.00 from Pac Brake). In any case, if you do remove the original unit, I'd suggest you at least get new clamps from Pac Brake.

Despite what some people may tell you, this is not a 30-minute job. If you must remove the unit, plan on at least 2 hours. Pay particular attention to aligning the Pac Brake properly. It is very easy to install it only to find it has a noisy leak (especially at the end connecting to the exhaust pipe).

Lastly, take a good look at the exhaust manifold. It is not all that uncommon to find a crack or break just to the right of the outlet to the Turbocharger.

If you wish, contact me directly and I may be able to help you with this.

[Happycarz]

Look for something like this:

[gene409]

You guys are great! Heres where i am today. I found the pacbrake under the coach about half way between the rear duals. I have the clamps (bands off) and the brake in my hand with the exception that it is still connected to a line (air correct)? The door looks to be in perfect shape but wouldnt budge. I pulled the bottom circlip loose (I wonder where that flew off to) and yanked the pin loose to separate the cylinder from the flap/door. The door flips back and forth easily. The cylinder i cant pull out for anything. Do we have a frozen cylinder at this point or could there be a multitude of relays, fuses, gizmos etc that put air into the cylinder when you press the red button? The serial number is pacbrake 6823 for whatever thats worth.

Ready for your next instructions!

[gene409]

I forgot to mention i did not try to pull the cylinder out with a large wrench and only by hand. I'll jump back under there and try some channel locks.

[gene409]

I think i have answered my own questions. I pulled that rascal out from underneath the coach and took it into the shop. I bench tested with 60psi, moved to 80 and on up to 120. That cylinder wont EVEN think of moving. I will call pacbrake tomorrow and hopefully i can just purchase a new cylinder. The rest of the brake looks great. As far as the mechanicals of this thing there is nothing to it! Now what all happens after you push the button until the air comes out at the cylinder might be another story but hopefully with your help i have stumbled on to my problem.

[rmmpe]

Gene,

Sounds like you've got it.

As I suggested before; unless the clamps came off rather easily and appear to be in good shape, you may want to consider new ones.
In any event, get Pac Brake's special lubricating oil and put a bit on each end of the butterfly shaft from the inside before you re-install the unit (getting it into the lower shaft bushing is very difficult and "Iffy" when the unit is installed).

Take your time when re-installing the Pac Brake to insure you have it seated properly (can you guess how I know about this?).

Good luck and God-speed in your travels.

[Mike Canter]

I bought some special high temp exhaust brake oil from the Cummins place and I drop some oil on my unit and cylinder on a routine basis.

[gene409]

I was going to leave this alone (I didnt want to wear my welcome out). The frozen cylinder i started working by twisting the shaft and before long it was moving. I wd40'd the shaft and got it working quite good actually. It would fully open with 60psi bench testing in the garage. I decided to go ahead and reinstall. I started the coach and let it build 120lbs of air and hit the pacbrake switch and nothing happened (I was being lazy and not pulling out of its building to actually road test). I then punched 1st gear with the brakes set and still nothing. It obviously doesnt work like this (meaning the coach air sends pressure because the switch is turned on...right?) Maybe it works off engine back pressure which would make sense. I think the thing is fixed (hopefully) but i will need to get it out on the road to be sure.

[chasfm11]

Please be very careful. PacBrake recommends their lubricant because it will handle high temperature conditions. WD-40 will not. The residual WD-40 that you have inside the cylinder could be a fire hazard.

Next to a head on collision with a cement bridge pillar, the most dangerous condition in a MH is an engine fire, IMHO. I'm paranoid about anything in the engine compartment that could start one.

[sjholt]

Break down and buy the new piston.
My brake wouldn't work properly so I installed a switch in the engine compartment so I could cycle it to see if it was working- it was a hit and a miss- mainly miss.
Oh ya- there is an air solenoid in the engine compartment that you can wire a switch to energize it any time you want for testing.
So I kept trying the switch and it suddenly stop working altogether.
Took the hose off the solenoid and found rubber plugging up the orifice in the hose end. I took the the hose off and cleared it and blew the heck out of it and reinstalled it.
switched it on and off- hit and misses.
Pulled the whole thing on and bench tested it and found out that the piston had rusted inside and was passing more air around the seal than the orifice allowed.
So I drilled out the orifice 3 sizes bigger and wa la-- she worked every time.
Reinstalled it and the motorhome was good to go.
As usual this was just before a trip.
I've been thinking seariously about the new PB.