High Idle quit

Just had all the brake calipers off and finished replacing all the guide pins on the brake calipers. While the coach was still up on jack stands with the wheels off I started the engine and tried to engage the high idle to get the air tanks back up to PSI, nothing happened. Turned off the engine and power switch, turned back on, restarted and still no high idle. Only thing I can think of is the parking brake was set with about 70 PSI in the tanks, maybe it didn't set enough to allow the high idle to engage. Just shooting in the dark here.

Chuck

P.S. Darn those brake parts are big, you really realize it when they are off the coach and on the work bench.

Why did u decide u needed or wanted to air it up at that point? To assist in the step of uncaging the chambers?

Were the parking brake chambers caged?

If any rotation of the driveshaft was allowed to occur when u started it and it can, even if u r in neutral, if the brakes were not all engaged in the rear. Then the computer thinks the bus is moving and it wont let that happen the high idle I mean. That will also give an antilock code too.

U should be very satisfied with yourself if u did this it is no small task. Well done mate! U should also be so happy u have drum brakes on the drives. Your signature says 2000 so u have a 99 chassis? Or do u have all 6 hubs disk on that year H? Getting a caliper off the drives on the chassis that have them is easily twice as difficult to get off as the ones on the tag and the steering. Putting them back in place is an absolute artform to learn. Oh ya Gill u should film me doing it for those thingies u do on the innerweb.

Yes, I'm betting the parking brake was not set.

Joe, sure buddy I'll make you a movie star!

The yellow button could have been pushed down too, I suppose but it would have been giving a warning beep. Button up and popped as if parked but brakes were caged that is my guess what occurred. Curious as to what brakes can on a drive axle on a 99 h chassis not sure.

Joe: Mine is a LATE model year 1998 chassis. I have disk all around and DDC IV, so I guess even though it”s a 1998 I got most of the 1999 model year stuff.
When picking up parts at Prevost Winter Garden I meet their Southeastern district trainer. He suggested airing up the bus and applying the brakes a few times after the job was finished and before the tires were reinstalled to review and confirm proper operation of the breaks.

Once the bus is back on the ground and driven do you think there is a chance the high idle will start working again?

Chuck

I'm curious what tool did u use to remove the bottom slide pin on the drive axle caliper.

Joe:
Had a local shop in Tavares, FL do the job. Was on the road to Prevost Winter Garden doing parts run for tappet boots when rear calipers were removed.

Shop charged 11 hours @ $95 per hour, that included all six caliper pin rebuilds and replacing the tappet boots on the drivers side drive axle. Had them put in new pads too. Old ones still had 1/3 to 1/2 left but while it was apart might as well drop in new pads, they are not that expensive. Balancing weight fell off of inner drive axle wheel, shop rebalanced the wheel in that time & price too.

Chuck

Back to High Idle issue:

Per drawings, fuse for parking brake signal is good, relay for parking brake signal to high idle signal is good, the two items just mentioned (Parking brake switch and high idle switch) when activated, by pass the throttle petal and tell the ECM to increase RPM's, SO if the throttle petal works with out the high idle turned on it means the throttle signal is getting to the ECM. Not sure were to look from here.

Chuck

The only way the mechanical process of doing brakes can inhibit the high idle is as I suggested. If u start it with the brakes caged with the rims off even in neutral the driveshaft is slowly turning and the antilock sensors think the bus is rolling and the high idle wont go. If u put the rims and tires back on and it still doesn't work I would think it is unrelated to the work preformed.

I've triggered the antilock warning like this. When it does it resets itself before traveling 1 mile.

The place u found to put new dust boots under the tappets on the calipers.........prevo wont do that. U can get the kits to do it from prevo but prevo will discard the calipers if u bring one to them in that condition and sell u a new caliper. Their reasoning is the tool to do it is too costly. Ain't that something. U r going to have to give me that shops contact info so I can use them to do some discarded calipers with the same issue I've been gifted, next season, when I come back down.

I am fairly confident I can make the tool and I'd like to see what they r using before moving forward on potentially doing them myself in the future.

Found the problem with high idle.
Pressure switch in front drivers compartment RH side for parking brake signal and high idle signal was bad.

Chuck

Chuck, good find.

BTW, what shop did you use in Tavares? There are a few Prevost owners in and around there.

Coach Crafters. Their main business is rebuilding city and transit busses. They have been doing RV repair too. Shop is out in the middle of nowhere, kind of a industrial kind of place, nothing fancy, not to clean, but they do know the big busses and get the job done

Chuck

P.S. They do frame and paint work too

Get on the horn Jamie add them to your sponsors.

The amount of time they billed u was what someone who knows what they r doing should take to do it without rushing or wasting any time. That's what sticks out to me. The hourly rate is very fair. If there was no MIFs and the service writer is agreeable(this is VERY IMPORTANT to me, often lacking). This could be a good resource, time will tell.

I bet I could be a very interesting service writer for someone!!

Mechanic that did my caliper pins used to work at a charter bus company in Orlando, FL and he did all the brakes on their MCI & Van Hool busses. He said they all had Knorr Bremen brakes