I thought I pass along what’s been done over the last year plus with the chronic low intake boost pressure problem that showed itself through the check engine light being illuminated and the engine going into a derated mode of operation.
First the good news! CAT issued a new software load in the late summer or early fall time-frame that broadened the range of acceptance for the boost pressure. This has eliminated the alarm condition. The load made other changes, the specifics I don’t have. It has been rumored that the load also changed the firing of the regeneration system.
The symptom of the low intake pressure has been taken care of, but was there an underlying problem? My coach and least one other coach were used for data collection. On my coach they ran it on a chassis dyno to simulate maximum load. While running it through its power band they collected pressure readings on both sides of the Charge Air Cooler (CAC) or Air to Air Cooler (ATAC). The results would show the pressure drop through the CAC. My regional CAT service representative said the results indicated the restriction through the CAC was at CAT’s threshold. To me that should say that the CAC is acceptable. FYI, there was zero restriction through the CAC up to 20psi and a maximum restriction of 2psi at WOT.
CAT worked with Modine, the CAC manufacturer, to get a new less restrictive design completed for testing. Although that testing was to occur on my coach, it was conducted on a west coast coach. CAT concluded the new design and testing were successful. Monaco RV has assigned the new CAC a part number and it’s available for purchase now. The price is $1692 plus freight!
A bit of okay news here is that this replacement is not required; remember CAT corrected the alarm condition. Also realize CAT told me that my CAC met their requirements, but was right at their threshold. BTW, I asked for the CAC design specifications that should have been available to anyone buying CAT engines. I was told that information was not available to the public. For those that go through with this change will likely gain some performance at higher engine loads and will likely have better fuel mileage. Those that don’t elect to make this change should not worry about hurting the reliability of the engine. The restriction does not lead to increased pressure anywhere in the system. Our engine has a variable vane turbo that is controlled by the ECM from pressure readings that it gets from the unrestricted side of the CAC.
The unfortunate reality is that this change out would have been paid for by someone other than us if Monaco Coach didn't go out of business. I’m not suggesting Monaco Coach would have been responsible, just that without a Monaco Coach to defend themselves, CAT is saying it’s Monaco Coach’s issue. Just so you know, engine manufacturers must approve add-on systems when they can directly affect the engine. What should have happened is that Monaco Coach should have provided their CAC engineering data to CAT for approval. CAT should have approve the engineering data and likely would have conducted first article testing to verify what was engineered on paper was actually designed and installed as engineered. Monaco RV cannot locate CAT’s certification of the Monaco Coach design. If the CAC was undersized, and remember CAT said mine was at threshold, then the fault could be CAT’s, Monaco Coach’s or Modine’s.
A bit more bad news for anyone wanting to make this change, the Replacement CAC is not a direct replacement and some modifications will have to be made. My CAT service rep would not run down what the modifications were on the coach they installed the replacement unit in. I know their goal was to get a form and fit direct replacement. Unfortunately, they probably discovered that was not possible while meeting their lower restriction requirements.
I spent over a year working this problem to resolution and didn’t expect the final outcome being one where we owners would have to foot the bill. Given I haven’t had any performance issues yet (I haven’t driven any of the west coast mountain ranges), I will not be making this upgrade. For CAT owners outside of CAT’s eastern region, it’s possible your regional service representative can help with some goodwill—my rep, Steven Goggin, will not.
If anyone does this replacement, please take pictures and notes on what modifications are required. That would be great information for anyone that follows.
