Cat vs Cummins

[davesparks2001]

WE are considering trading our 36' gas coach for a diesel pusher. I've been trying to educate myself before getting too deep as this represents a major investment for us common working class people. I've read some horror stories about the C7 Cat which seems to be very popular in the 40' DP segment. I haven't really seen anything negative about the Cummins so I was looking for feedback from you folks with more experience than I. Should I only consider coaches with the Cummins?

[Smitty77]

Davesparks2001 - You did not mention your budget range...

But assuming that you can always drop years to remain in budget range, I'll share my thoughts on engines for 40' or plus DP's.

1) Buy the largest displacement CAT, Cummins or Detroit engine you can. This usually moves you up into the higher quality coaches, which is a good thing too.
2) BIG BLOCKS provide more HP/Torque, and do not need to work as hard as mid size (ISC/ISL or C7/C9). Quite often by working easier, they provide the same, if not even better MPG. (Coach dependent, based upon gear ratio's too.)
3) BIG BLOCKS can usually be found with 2 or 3 Stage Jake Compression Assist, and or liken Foretravels, Retarder equipped Allison Transmissions. IMO, a great safety feature is having plenty of Braking HP for mountain decent. Especially if you plan on towing any have toads, or say a trailer too.

CAT vs Cummins vs Detroit? I'd take any of them. I would just do your homework on the specific manufactures and models that you like, that come equipped with a BIG BLOCK engine.

I've always recommended to 'Drop years to remain within budget, and buy the highest quality coach that you can.'. I also suggest reserving a cushion of funds to do any catch up maintenance that maybe required. Establish a baseline of condition so you know what needs to be maintained going forward.

If you decide that you are mostly flat land traveling, nothing wrong with a ISC/ISL C7/C9 mid block engine. These are usually in either entry of mid level coaches, and quite often do not have as much weight as the higher end coaches. So the power to weight ratios can be favorable.

I personally lost the battle, made one heck of a mistake. Let the DW look inside of a 40' coach that had the largest galley we'd ever found in a coach. While I was lucky this was a coach on our short list, I was unfortunate that it had a mid size block Cummins ISL engine. While the Power to Weight ratio are 'OK', and we have now traveled 45K with it, I do wish I had been able to hold off until we found one our preferred models that had the optional BIG BLOCK engine. (This is a Country Coach Allure, a well built coach. My sweet spot for the CC line was the Intrigue, with the optional C12/C13 BIG BLOCK.)

Happy hunting, and when you get the new ride - enjoy!!!
Smitty

[Kayteg1]

RayChez wrote:
Kayteg1, years ago all diesel engines smoked because the fuel was not refined like the #2 diesel is now days. Also if you had a bad injector they would smoke black really bad. But now with the ULSD you never see a diesel engine smoke whether it is Cat or Cummins or even Volvo or DD.
Engine technology has really improved because of the emission laws imposed, but it has taken some time because at first it was doing more damage to the engine then good.

You are right about the improvements, but still those older CAT have been heavy smokers.
The 3208 CAT were 1980's generation. Later on I bought coach with 1972 Detroit engine and older, 2-cycle diesel smoked much less than those CATs.
Maybe that is why CAT could not continue with on-road engines?

[mpierce]

NONE of the newer diesels smoke, unless they are failing. Even my 2003 CAT C-15 does NOT smoke. Anything built within the last 15-20 will NOT smoke, unless it is either failing, or it has been turned up by a PO. ie, overfueled.

[RayChez]

Kayteg1, years ago all diesel engines smoked because the fuel was not refined like the #2 diesel is now days. Also if you had a bad injector they would smoke black really bad. But now with the ULSD you never see a diesel engine smoke whether it is Cat or Cummins or even Volvo or DD.
Engine technology has really improved because of the emission laws imposed, but it has taken some time because at first it was doing more damage to the engine then good.

[Kayteg1]

Take my experience with a grain of salt as I did own 2 coaches with older CAT 3208 (hope remember the code right).
They performed well, but smoke like hell.
When towing my boat at Lake Tahoe (6000 elevation) - starting at green light I had to wait for all the traffic behind me to pass before I could accelerate.
Once I did, nobody on my right side exhaust could see anything anymore.
I did try to adjust them, used diesel purge - only to conclude that was the nature of the beast.

[RayChez]

I have had both and the 3126-E Cat engine through 70K miles has been a very good engine. Get 8-9 mpg.

And the person that wrote that Cat engines give lots of problems does not know what he is talking about. You can go through the archives in this forum and the only problem with the rear radiator coaches was the slobber tube that did not have the extension and was getting oil on the radiator which needed cleaning, but if the extension was on like it was on mine you would never get a drop of oil from the slobber tube. Fact if you added the proper amount of oil instead of over filling, you would never have a problem with oil coming out of the breather tube.

Now back to the archives in this forum and you will find all kinds of problems with the ISB Cummins which was blowing holes on the side of the blocks. Blocks that were manufactured in south america. Also the ISL engines had problems with wrist pins that were not machined right and were causing engine failures. Cummins did install a light on the dash that would tell you when the engine was about to blow up.

I also worked with massive Caterpillar engines on locomotives and they are hard to beat.

Reason why Caterpillar and Mercedes got out of the RV business was because the emissions by the federal government was too strict and it was not worth it to the company since they already had plenty of other projects in the construction business.

But both engines will last you a life time If you take care of them. Cummins seems to have finally straightened up their act and are NOW producing some good dependable engines. But they had lots of problems a few years ago.

Wolfe10 had some very good links on the problems Cummins had with the wrist pin situation on another thread.

[sprintmod1]

First of all, I have owned both engines. They are both great engines if properly maintained. My short explanation would be that if you have CAT, you have tons of immediate get up and go from a stop and that power will come at a price and that price is the lack of fuel milage.

If you have a Cummins, it will take its good old time getting you moving on down the road, but it will move you down the road and reward you with much better fuel milage than the CAT.

If some sort of a problem shows up with either engine, yes, it will cost money.

[Busskipper]

Ivylog wrote:
Can't get my search to post so advanced search on this subject in over a year old and class A and you'll only find 618 posts.

The small Acert engines (C7) is not as bad as the larger ones.

Cat

Don't you love what they've done to the forum to prevent you from posting a search!!!!!!!!!!!!!!!!!

More than a few choice words #*#@!*

[bobkatmsu]

One misconception that many non-diesel people have, is that diesel engines go 300, 400, 500 thousand miles with little problems. Talk to any diesel mechanic and they will tell you yes you can get that many miles out of a diesel, however, starting about 150,000 you will start experiencing major $$$ issues. They can be fixed and the engine will go for ever, but it is going to cost you dearly.

[horizon36]

The 3126E CAT in our coach has worked flawlessly with regular maintenance. Ours is set for 330 Hp and 860 torque. I think it has Clydesdale sized horses that do a great job of propelling my coach.

[Mr_Mark1]

Trackrig wrote:
I have a Cat C7, no problems, I like it. I have a preference for Cats just because I've been around them a lot more. I haven't met anyone with any more problems on a Cat than on a Cummins. Don't worry about which engine it has.

The main problem people have with either one is not keeping the radiators clean to prevent over heating. One friend with a Cat had to pull his radiator and inter cooler to get them clean due to the previous owner. Another friend with a Prevost / Cummins never could get it to stop over heating so he traded in for a newer Prevost which also has a Cummins and does fine.

Bill

Prevost coaches originally had Detroit Diesels installed and now have a Volvo engine.

If a Prevost has a Cummins engine, someone removed the original.

MM.

[Valkyriebush]

My Cat 3126E has been flawless 75K! Except a manifold gasket leak last year.

[Tom_Barb]

Most folks that do their own minor maintenance prefer the cummins. bleeding the fuel system after a filter change is easier on the cummins, the big "I" 6 doesn't fill the compartment as tight as the Cat. When you find the coach you like the engine isn't a deal breaker.

[Trackrig]

I have a Cat C7, no problems, I like it. I have a preference for Cats just because I've been around them a lot more. I haven't met anyone with any more problems on a Cat than on a Cummins. Don't worry about which engine it has.

The main problem people have with either one is not keeping the radiators clean to prevent over heating. One friend with a Cat had to pull his radiator and inter cooler to get them clean due to the previous owner. Another friend with a Prevost / Cummins never could get it to stop over heating so he traded in for a newer Prevost which also has a Cummins and does fine.

Bill