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12-06-2024, 04:18 PM
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#1
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Member
Join Date: Jun 2020
Posts: 92
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(2005) CAT C-9 engine failure
While traveling home from a Thanksgiving’s lake trip, my engine exploded! Knocked holes in the block and oil pan. Running at 67 MPH on the interstate hwy. 43,343 miles on the engine. 3100 miles since the last oil change.
I’ve owned this motohome for 12 years. It had around 22K miles when I bought it 2012. Thoughts on possible cause?
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12-06-2024, 04:58 PM
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#2
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Senior Member
Join Date: Jun 2021
Location: Hayden, Al
Posts: 277
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Sorry for your trouble, but I think this would come under the S**t happens file, as a rule "Cat" is very dependable power plant, but for some reason yours was the 1 in a million.
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2007 Tiffin Phaeton 40QDH
2003 Honda Element / 2016 SlingShot
Alabama "Roll Tide"
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12-06-2024, 05:10 PM
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#3
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Senior Member
Monaco Owners Club
Join Date: Feb 2023
Posts: 596
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Any sign of sudden or instant loss of oil pressure prior to *BOOM*?
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2008 Holiday Rambler Navigator Bismark IV 45ft
15L Cummins ISX (525HP)
Allison 4000 series in Roadmaster S Chassis
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12-06-2024, 05:35 PM
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#4
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Senior Member
Join Date: Jun 2021
Location: Western Slope of Colorado
Posts: 425
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Wow, what a drag.
I'd bet it dropped a valve.
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04 Monaco Monarch 30 PDD on Ford F53 chassis V10
97 Monaco Executive 40ft - SOLD, downsizing
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12-06-2024, 08:17 PM
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#5
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Senior Member
Join Date: Apr 2024
Location: WI Driftlesser
Posts: 2,586
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Yes, stuff happens. I bet it's more like 1 in 100 fail before 50,000 miles. Could even be 1 in 100 fail before 10,000 miles? Could have scuffed a piston, from injector failure, or oil jet plugging. Or could have just been a defective rod? Probably never know without spending good money after bad on an engine tear down. The rod doesn't show any color that I can see.
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12-07-2024, 02:52 PM
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#6
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Member
Join Date: Jun 2020
Posts: 92
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Quote:
Originally Posted by Dieselboy
Any sign of sudden or instant loss of oil pressure prior to *BOOM*?
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This engine has a HUEI pump. Without sufficient oil pressure the fuel injection ceases to function. Typical oil pressure before the engine is at 205 F is high.
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12-07-2024, 02:56 PM
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#7
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Member
Join Date: Jun 2020
Posts: 92
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Quote:
Originally Posted by hastemaker
Sorry for your trouble, but I think this would come under the S**t happens file, as a rule "Cat" is very dependable power plant, but for some reason yours was the 1 in a million.
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I understand CAT was building “lightweight” C9 for motorhomes that cost less than a Cummins 5.9
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12-07-2024, 03:00 PM
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#8
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Member
Join Date: Jun 2020
Posts: 92
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Quote:
Originally Posted by Max Headroom
Wow, what a drag.
I'd bet it dropped a valve.
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Would a dropped valve cause this much damage?
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12-07-2024, 03:16 PM
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#9
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Member
Join Date: Jun 2020
Posts: 92
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Quote:
Originally Posted by SafariBen
Yes, stuff happens. I bet it's more like 1 in 100 fail before 50,000 miles. Could even be 1 in 100 fail before 10,000 miles? Could have scuffed a piston, from injector failure, or oil jet plugging. Or could have just been a defective rod? Probably never know without spending good money after bad on an engine tear down. The rod doesn't show any color that I can see.
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I use synthetic oil (Amsoil). Had an excellent oil analysis last year. I currently tow F250 truck with a golf cart in the truck box. About 7700 lbs. on 15K rated hitch. I’ve a dash cam, the engine failed when the motorhome rolled over an insignificant bump in the road.
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12-07-2024, 03:20 PM
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#10
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Senior Member
Join Date: Mar 2024
Location: Bohemia NY
Posts: 2,020
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I can't see from the picture. Is the rod still able to turn on the crankshaft or did the bearing seize on it? Was it that twisting action that broke the rod? If the bearing is seized on the crankshaft, then it either wore and then the shells collapsed, or debris got into it. If debris it is due to a highly gunked up engine or something got in at the last oil/filter change. Is this home now? Can you drop the pan and remove the rod to determine what happened?
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Dennis
Bohemia NY
2008 Nimbus 342 SE Carlyle
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12-07-2024, 03:31 PM
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#11
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Senior Member
Join Date: Jun 2021
Location: Western Slope of Colorado
Posts: 425
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Quote:
Originally Posted by kwbullin
Would a dropped valve cause this much damage?
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Yes.
Head of the valve can fall on top of the piston, then when the piston comes up to TDC next time around, the valve is taking up a lot more space than the TDC gap for compression. Sometimes the valve just breaks the top of the piston, but sometimes it just stops it cold while the rest of the cranktrain tries to keep going trying to compress the uncompressable valve head. Something has got to give. Usually it's the rod.
Clues are, bottom of rod still attached to the crank, rod broken at a thin point. Also the big end of the rod will not be discolored like being overheated from lack of oil.
Why?
Many valves are made from two pieces. The head, and the stem.
Most of the time, under normal use, they hold up just fine. Most of the time...
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04 Monaco Monarch 30 PDD on Ford F53 chassis V10
97 Monaco Executive 40ft - SOLD, downsizing
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12-07-2024, 03:40 PM
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#12
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Senior Member
Join Date: Mar 2024
Location: Bohemia NY
Posts: 2,020
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There is also the possibility of an injector failure filling the cylinder with fuel or even having the head break off. For the valve failure there could be that Chordal failure like on the Cummins early ISX. ??? With the low mileage for its age this engine has sat a lot, been short cycled, and likely abused in other ways. Really have to take it apart a bit to figure it out. Enquiring minds want to know.
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Dennis
Bohemia NY
2008 Nimbus 342 SE Carlyle
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12-07-2024, 04:10 PM
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#13
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Senior Member
Join Date: Mar 2024
Location: Bohemia NY
Posts: 2,020
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Quote:
Originally Posted by kwbullin
I understand CAT was building “lightweight” C9 for motorhomes that cost less than a Cummins 5.9
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The lower range engine for CAT was the 3126 or later C7. It was a 7.2 liter usually in 300, 330, or 350 horse trim for motorhomes. It was a lower cost alternative to the Cummins 8.3L of the day. It was a parent bore block. The C9 and above are all higher end engines. They left the on-road business in 2010 though instead of dealing with the emissions stuff.
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Dennis
Bohemia NY
2008 Nimbus 342 SE Carlyle
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12-07-2024, 06:07 PM
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#14
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Senior Member
Join Date: Apr 2024
Location: WI Driftlesser
Posts: 2,586
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Going with the bump in the road hypothesis, it could have been something that worked loose in the intake manifold, then took out a piston or valve, that let the rod loose? Cummins had heater grids do that, cat used heater grids on some engines, not sure about the C9?
I'd think it's unlikely a failed HEUI injector would hydrolock an engine at highway speed. It could melt a piston causing a seizure.
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