Engine Temperature Fluctuation - Concern or Not?

[fagnaml]

Quick update for my cooling system.  This past Friday (11/1) I took the motorhome to Cummins Coach Care (located a bit northeast of downtown Houston) as I've had superb service from them.   Justin McDonald, a very knowledgeable, very customer focused shop supervisor found the following:

• There was a Cummins recall for ECM programming but because my engine was never registered by the original owner (nor me!) the recall work was never completed.  The new programming has some improvement to engine temperature control along with other improvements (what I don't know yet)
• The Horton fan clutch is performing as it should
• Radiator and charge air cooler all easily passed pressure tests
• The coolant was very clean with no signs of rust, particulates or other contaminants.  The coolant quality was good per SCA test strips.
• Expect to see very little of anything when the cooling system is flushed tomorrow.
• The themostat showed some "scoring" and has some sticking as it was manually opened
• Because of the type of level probe Freightliner installed in the coolant tank, the "purple" heavy duty coolant with SCAs is required i.e. can't change to the red extended life coolant without changing the level probe.
• Found the engine block heater to have "darkened" wires -- heater will be replaced

The ECM programming update, engine block heater and thermostat replacement fall under the Cummins five year, 100,000 mile warranty so no cost to me except for $100 deductible.  I'll still need to pay for coolant change / flush service.   

Per Justin, this work should help stabilize my engine temperature some, but on a hot 95 F+ day still expect to have the fan go into / out-of high speed to maintain engine temperature.

Any comments from the Forum on the above findings?

[wolfe10]

Mike,

Let us know how the update/upgrade work in the "real world".

[fagnaml]

Quick update on my experiences.  Replacing the "scored" thermostat helped as the new thermostat starts opening as it should at ~190 F and is fully open at ~195 F.   Engine temperature holds in the 195 - 205 F range with an occasionally up-tick to 210 F at which time the fan goes into high speed to cool the engine down to ~187 F.    Cummins Coach Care Houston confirmed my Horton clutch is functioning properly.   The fan speed cycling is "normal" per the Cummins shop supervisor (Justin McDonald) to help maximize fuel economy. 

I also had a "stupid me" moment with Justin.  He reminded me my previous motorhome (2007 Damon Astoria) had a 300 HP 5.9L ISB engine with a five speed Allison 2500 MH transmission.  With that "set-up" my engine speed was ~2200 RPM at 65 mph which provided considerable more fan air flow to keep engine temp ~190 F.   My current "set-up" is a 360 HP 6.7L  ISB with a six speed Allison 3000 MH transmission.  At 65 mph my engine speed now is ~1600 RPM meaning reduced air flow versus what I was "used to experiencing".   Justin assured me everything with my cooling system is working as it should!  

I had zero problems during my November jaunts between Houston and Baton Rogue to watch the LSU Tigers go 12-0 in regular season play.  

[fagnaml]

Quick update about my fluctuating engine temperature experience.   I haven't taken the coach out for a fun weekend journey since the last weekend of November but it has been out for its monthly 45 minute drive.   With cooler ambient temps during December - February the temperature fluctuation between 187 F and 207 F continued but not as frequently.   Since my last update, Justin McDonald at Houston Cummins Coach Care provided this simple narrative on my cooling system design and ECM control.  As previously noted, the ECM "modulates" engine temperature between 187 F and 207 F.  When the engine temp reaches 207 F, the fan control switches to high speed to cool the engine to 187 F at which time the fan returns to low speed mode.   Per Houston Cummins, this fan speed modulation is one of several ways Cummins uses to achieve somewhat higher fuel mileage.

The wife and I are taking the coach to the Texas Hill Country the weekend of March 27 - 31 to enjoy the Wine & Wildflowers Journey.  Will let the forum know how the cooling system performs.

 

[hermanmullins]

Nice chart.

When your temp rises you can always drop down a gear which will increase fan speed and in most cases lower your temp. 

Herman 

[five]

One more comment on a coolant filter.  I called Freightliner prior to having my coolant changed.  They said no coolant filter, they don't use them.  Much to my surprise, when we were draining the coolant, we found a coolant filter that was virtually totally plugged with crud, sludge and similar 'stuff.'  So what happened was that DD put the filter on at the factory and Freightliner did not know it.

[manholt]

FIVE, be happy that DD & Factory did.  One reason I don't like or want Freightliner...they experiment on your dime!  All that crud would have been going into the DD500!  Replacement cost?

[jleamont]

Funny, we had a bunch of DD13's at work that didn't come with a filter, recalled them back, installed filter, put it right on the frame next to the passenger side tire (no body said they were smart) 3 years later, recalled them again and pulled them off, after we had several leak from getting punched with road debris. I asked why? we made a mistake....which time?? no response. 

[five]

Carl, that's what the tech said that was changing the coolant.  Also, Freightliner told me the coolant system took 32 gallons....yes gallons.  Actual capacity was about 15 gallons.

[manholt]

It's a learning curve!