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Old 01-06-2019, 07:47 AM   #1
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Paranoid about early ISC 8.3 Reliability

Ive been looking at older DPs most have either a mechanical 8.3 or the early electronic isc. I feel relatively confidant of the mechanical one but the seemingly endless stories of the isc problems make me wonder if its a time bomb waiting to go off. If I stay mechanical im stuck with a very small selection of decent coaches, the newer engines give me more selection of units and features but I dont want a disaster in the making. How bad are the early ISC,s?
Im not ready to full time yet so this would be a weekend travel machine but once a year have to go on a longer 3000 roundtrip.
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Old 01-06-2019, 08:11 AM   #2
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Where I work we have 4 8.3 engines, 3 mechanical injection, 1 with the caps fuel system. 3 of these are in fire trucks, so they are driven hard. The guys don't care about it, just get there fast. The 4th one is in a vactor truck, pretty much overloaded at all times. All 4 of these engines have been great. When I was looking for my motorhome I was looking for an 8.3 because of my experience at work. I ended up getting an 8.9. I would not hesitate to get either one.
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Old 01-06-2019, 08:22 AM   #3
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I have a 170K on my ISC plenty of power with no problems. Take the chance and roll the dice.
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Old 01-06-2019, 10:17 AM   #4
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The key word in your post is "seemingly". Not sure where you are getting your information. These engines are renowned for being bulletproof. I have the CAPS era ISC 8.3 uprated to 350 hp which is the most Cummins will authorize. In 18 years it has seen 85K trouble free miles.

Out of the hundreds of things that can go wrong on these complicated machines, that big diesel engine back there is the last thing I think about.
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Old 01-06-2019, 11:35 AM   #5
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What years are “early”?
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Old 01-06-2019, 11:42 AM   #6
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First off the 8.3 is a good workhorse they do fine in moderate sized Motorhomes. I know guys with small dump trucks that overload the trucks bad and the motors grunt and groan but dont give up. You will have a hard time killing one in a Motorhome unless the previous owner did no maintence what so ever.
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Old 01-06-2019, 11:50 AM   #7
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1999 thru prob 2004 coaches are likely to have an ISC and some an ISL both based on the caps fuel system. And as long as you dont have any leaks at the pump housing, they just work. After 2005 you are more likely to have some type of particulate filter and more electronics for injector control.

Mine gets 9.3mpg at 62cruise for the last 6000 miles (2 trips to maine and back from tx). Rarely downshifts on hills and then will still stay 56mph at 25lbs of boost.

Its not the drivetrain you need to worry about. Most coaches that age are starting to need major repairs. You better be prepared to throw some $ at it.
2003 Scepter 40PDBB - Roadmaster RR8S - Cummins ISC350 - purch aug16
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Old 01-06-2019, 11:54 AM   #8
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ISC? Great engines.

The problem child Cummins seems to be the ISX; there seems to be cylinder 6 valve failure problem with them in motor homes...
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Old 01-07-2019, 07:21 AM   #9
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I absolutely love my 8.3 ISC — 350 HP. No DEF and no DPF.
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Old 01-07-2019, 08:36 AM   #10
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Originally Posted by apatz View Post
I absolutely love my 8.3 ISC — 350 HP. No DEF and no DPF.
DITTO for my 2004!
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Old 01-07-2019, 04:28 PM   #11
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The 8.3L Cummins ISC is a great engine. The only common problem with the Cummins ISC is a cracked exhaust manifold. Just change it to the newer design.
Some folks are still running a Banks kit on on an ISC with over 400hp.

Are you confusing the ISL wrist pin issue with the ISC?
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Old 01-08-2019, 09:12 AM   #12
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Hello - how do I know if I have an old or new design of the exhaust manifold ??


2002 ISC 350
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Old 01-08-2019, 09:16 AM   #13
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Originally Posted by apatz View Post
I absolutely love my 8.3 ISC — 350 HP. No DEF and no DPF.
So far, so good!
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Old 01-08-2019, 09:53 AM   #14
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Alan you can have Cummins check out the manifold for you and tell you if it a new style if the person had it done at a Cummins shop it will be in the records system.
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