[Marshall]

We have a few guys on here with a DDECV era coach 06,07 mostly.

Don’t wait until you climb Eisenhower to check your CAC. You can do a simple spray water test on the CAC.

Start your engine and spray water on the lower portion and edges of the CAC tubes. If you see any bubble’s it’s done. Change it.

Search Duralite on here and you will see pictures and know what were talking about.

TN I’m curious what their gonna hit you for between shipping and install, good luck.

Later

bv

[Archived]

I would think a town the size of Denver has a place to get the CAC

IF it’s not too late call some local bus or charter companies and see where they get theirs. Some companies using Prevost or even parts houses like NAPA.

[Archived]

I tried all the biggies in Denver, but couldn’t find anyone with a CAC. Stewart & Stephenson is doing the work. Their Lead Tech is on the case. He’s been there forever and seems to have a very good grasp of the issue.

The part was just under $1500 and shipping about the same. The funny thing is, I left Nashville a few days ago! Could have brought it with me had I known!

I’m changing the hoses and clamps while they are in there.

[Jon]

Well…..I thought I would fill in some of the details of my findings. Hopefully this will help someone in the future.

Background: I hit the first climb west of Denver up into the mountains and had almost no engine pulling power up the first major climb. Down to 22 MPH in the far right lane! Boost gauge on the dash showed full boost, but no power. Also, no abnormal smoke out of the exhaust. I did get one notification in the driver display “check engine at next stop”. It quickly went away and I only saw it once.

What I learning through this whole adventure: Apparently, my Charge Air Cooler (CAC) had a significant breech. Given the variable vanes on the turbo, it was barely able to keep up boost pressure, but was running wide open. When I finally got the coach to a shop for diagnosis, we first read the ECM codes and only found a few. This is the explanation given to me be the Lead Tech at Stewart & Stephenson. Makes sense to me……

Low/high boost pressure – Turbo was running wide open and apparently was not able to keep up at one point and threw the low boost error

High exhaust temp – An underperforming CAC (think turbo intercooler) will not cool the intake air sufficiently and thus drives the exhaust temperature up. ECM caught that event.

De-rate – Once the ECM sensed a high exhaust temp, it “de-rated” or reduced the HP output to help cool the over-temp exhaust. That’s when I was trying to climb that first hill and had no power.

I pulled off into the chain-up lane near Genesee Park while I tried to figure out what had happened. I knew I needed to turn around, and the chain-up lane was a perfect place do plan my return. Apparently, while the bus was sitting idling in the lane, it cooled the exhaust sufficiently to clear the de-rating of HP. When I started out again, I had close to normal power until I hit a small climb coming back into Denver, when it happened again. Fortunately, I was at my exit at that point, so it didn’t matter.

The good news here…..our coaches are well designed and have the necessary protections to keep from doing significant damage when parts fail. I’m sure someone will ask if I didn’t feel it while on flat land……No….maybe. The coach was able to maintain highway speeds and still had pedal to go. It pulled up small hills just fine. Maybe MPG was down a bit. Dash gauge indicated full/near full boost. We don’t have Pyro’s on diesel engines anymore, or I most likely would have seen the high exhaust temps.

My coach is 14 years old, so it’s hard to blame Prevost for a failed CAC. There does seem to be a high failure rate on CAC’s of my coach vintage. I would have liked to see this covered in a campaign to repair, but I guess I understand.

Hope this helps others either get serious about having your CAC checked (at least the easy check) or self diagnose a low power situation.

[Jon]

Marshall, you are being kind in not attributing any responsibility to Prevost.

There are numbers of us who would not be so charitable. During the period when we were replacing CACs left and right it was reported that the OEM CAC was of lesser quality, certainly had a failure history, and its only value was the supplier met the documentation requirements imposed by Volvo/Prevost.

The replacement CAC you are getting was available from Prevost as a replacement part, but never as OEM. Maybe that has changed, but it is sad that the CAC, like fan clutches had a shorter life than the average house fly when there were far better alternatives.

Your new CAC is so highly regarded by its manufacturer it has a 7 year, million mile warranty.

[Rudy]

Thanks Jon,

No sense beating your head against a wall with Prevost. I’m just looking forward to getting my million miles out of the Duralite!

[Gerald]

Marshall, your ECM is who sees your pyros to monitor exhaust temps

[Larry & Diane]

$1500 buck shipping. Charter Jet , First Class.

[gary]

By the way……coach performance is amazing. Much stronger pull now. 50+ MPH up the climbs and down into Breckenridge. Once I hit the tunnel, I was at 35 MPH, right lane, 3rd gear and modulating between stage 1 and stage 2 jake. The only time I hit the brakes was to slow down for trucks going slower than me.