Thoughts on 2005/2006 Cummins ISM 500/ Allison 4000?

GREAT CHOICE! Both engine/transmission combo and coach builder.

If I ever win the Powerball an Essex will be our first purchase. Yeah, I'm a fan. :B

Pull an oil sample and send it to Blackstone labs, do the trans as well. That will tell you (for 50 bucks) if you are looking at mechanical issues.

if I won the lottery (doubtful), I'd order a Prevost with a 500 horse DDEC and a 6 speed Allison with retarder. Go big or stay home.

Wishful thinking on my part...lol

Bruce Brown wrote:
GREAT CHOICE! Both engine/transmission combo and coach builder.

If I ever win the Powerball an Essex will be our first purchase. Yeah, I'm a fan. :B

Well we have been looking for around 6 months for a, older like new coach at a price that we could afford. We have found a few but they get snapped up quick. I hope that we can make a deal on this one.

SidecarFlip wrote:
Pull an oil sample and send it to Blackstone labs, do the trans as well. That will tell you (for 50 bucks) if you are looking at mechanical issues.

Thanks for the idea; I have an oil analyses lab a few miles from my home that I used several years ago. I may have to stop by and pick up a few sample kits.

I've got close to 100,000 miles on my coach with zero issues. Great engine. Mine was chipped to 525HP but IMO that was a waste of money. Plenty of power including several trips to Denver and Golden....Dennis

Great engine/tranny combo, great coach. Just make sure it has been properly maintained and everything works. Consider paying for a professional inspection for both the coach things and the chassis/running gear.

We looked at a 2006 Essex with same engine back in 2013 and would have bought it if it had not been smoked in by the prior owner's wife. We ended up with the County Coach we now have.

2006 will be pre DPF and pre DEF so that is a plus.

Executive wrote:
I've got close to 100,000 miles on my coach with zero issues. Great engine. Mine was chipped to 525HP but IMO that was a waste of money. Plenty of power including several trips to Denver and Golden....Dennis

Thanks

Did the power chipping you had done also disable the EGR system? In doing my research on the trucking forums, many seem to think that the EGR system has been the biggest source of problems with this engine.

Would you please share with me the name of the company you used or bought the chip from.

Over the years I’ve had the pleasure of having 2 different RVs with that combination. A 1997 Monaco Signature and a2002 Monaco executive. The 1997 had a bit over 200,000 miles without any i issues whatsoever with engine or trans. The 2002 has currently 70,000 miles, with out a single issue. The Ecec was bought with very low mileage Before purchasing we had a Cummins tech hook up a computer to the engine and he was able to verify engine hrs, and how many of the hours were idling and a lot of other info on the engine. Bottom line he said the engine was like new. You’ll love the power, and the 2 stage compression brake. I’ve had 5 different diesel pushers and that combination for a power unit has been the best.

2006 Newmar Essex? Hey, that's my coach!

I have owned this coach for over 3 years and 20,000 miles. I know a few things!

My coach has over 90,000 miles and is going strong. While all old coaches have issues, I think the Newmar Essex is a great coach and still has great support. I am glad I am a part of the Newmar family.

But, old coaches have issues. Mine is no exception.

The ISM 500 is hard on Turbos. Mine is on its 3rd one. If yours should fail, the only good option is a replacement by Cummins. My #2 turbo only lasted 7000 miles (less than 12 months). $4000 to replace.

The EGR system is a mess. You will have to deal with problems as they develop. My only issue in 20,000 miles is the EGR valve failed. $1800 to replace. Original owner had numerous issues.

There is speculation that the rear end (differential) is under speced for the weight. I am aware of several failures. I think the rear-end will run hundreds of thousands of miles... in Florida. But in the Rocky Mtn west, they wear out. Mine failed at 85,000 miles (near Florida, but this coach lived in the mountains). Cost $5K.

E-Plex. The central controller is obsolete and unsupported and will fail at any moment! The solution is to rework each system (inverter, tanks, water pump, AC and heater) and make them work with original equipment. You are basically making the ESSEX work like a mtn aire. I have done all this. Plenty of details over on IRV2. Cost, under 1000, except I also replaced the inverted with a much newer and better inverter.


If you buy a good coach and spend the money and effort to upgrade, the coach will work very well. I love mine and plan to keep it for 7 more years.

One concern I would think needs to be addressed is paint checking. It's worse with darker colors due to the fact that darker colors absorb more heat and uv. The fiberglass on 2003-2009 coaches is generally defective. Those that don't have it have generally kept their coaches in enclosed covered storage while those that park in hot sun most often do have it.

There is no fix for this issue without replacing the fiberglass. Even some very expensive older coaches have this issue.

When I inquired about some of the 2003-2009 coaches on rvtrader.com, most of the coaches had some form of paint checking.