On occasion the coach will not have much 'get up and go'. The first time it acted in this manner was one morning in September. I let the coach warm up, as we had our morning bowl of cereal, and pulled out. We were only going about half of a mile, and most of that was through parking lots, and I noticed a sound, as did my wife, Robin, that was a rhythmic and seemed to sound like air being released in time with the speed of the coach or the engine reminiscent of a steam engine. The morning was a bit chilly, but not cold, in the mid 40's as a guess. The coach may have been running at reduced power, but we were going through parking lots and were only on the road about 100 yards, so listening to the new sound had hold of our interest. Between games, I checked fluid levels, looked over the engine compartment for anything obviously wrong, everything normal. That afternoon, after the last game, we started the coach and left, the new sound gone and everything normal.

We live in eastern NC, we have taken the coach to southwestern Michigan, back through Nashville and have made about two weekend trips per month of about 400 to 600 round trip miles each without any problems, save one tire, but, as the cliché goes, that's another story.

After spending two weeks at Disney World for Thanksgiving, we start home. The sun is just setting, and it is a damp, misty drizzle day. Again, the new sound is back for the first time since that morning two months ago. As I pull out of the Fort Wilderness Campground acceleration in very slow. Half a mile to 45mph, two miles later 54mph was reached, thanks for flat Florida, but we could not hold speed on up the overpasses dropping back to 47mph, then back to almost 60mph on the downside and again to 54mph on the flat.

Robin had the manuals out and we are trying to reason through the issue. The only thing, at the time, that we could come up with was the PAC brake possibly partially closed, restricting the exhaust. After about an hour from leaving the campground we reach the first rest area, I engage the PAC brake and we make the stop. I check tailpipe for obstructions as well as the air intake, the PAC brake seems normal, I find nothing. I start the coach and notice that as soon as we start to move full power is back. We spend the night at a Wal-Mart in the upper eastern part of Georgia, get up the next morning and finish the trip home without a problem.

About a week later I move the coach across town, about 15 miles, and then back two weeks later or two weeks ago about the same distance. On both occasions the coach ran badly. The steam engine sound displays itself when the coach is moving slowly with the accelerator pedal partially depressed. When the pedal is fully depressed the sound goes away, but when slowing down and about 15mph or less is reached the sound returns. On neither of the short, most recent runs did the coach have full power.

quote:

Originally posted by Chris:
The only thing, at the time, that we could come up with was the PAC brake possibly partially closed, restricting the exhaust. After about an hour from leaving the campground we reach the first rest area, I engage the PAC brake and we make the stop. I check tailpipe for obstructions as well as the air intake, the PAC brake seems normal, I find nothing. I start the coach and notice that as soon as we start to move full power is back.

This does sound like a PAC brake sticking.

The PAC Brake is operated with an air switch - the air plunger engages the butterfly - this could be partially applied because the air in the plunger isn't fully venting from the release valve.

The PAC Brake has a butterfly shaft setup - the shaft inside of these tend to bend in the middle and stick - usually open.

I do believe you're looking in the correct area, now you'll need to check the air operation as well as the butterfly inside of the exhaust for it sticking every now and then.

Barthmobile site search result for PAC Brake

If you have a boost gauge what is it reading at that time. Take away the boost and you wonder where the power went. Waste gate may be opening up.

If it is the exhaust brake you could take the activating power off of it and see what happens

The problem was the fuel shutoff solenoid. It was moving about 3/8" and allowing enough fuel to flow to start the coach and run as described. The solenoid was replaced and the coach is again perfect.