Cummins 350 over heating

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toomas83

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Nov 5, 2018
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About 2 years ago my 2009 Winnebago Journey 34Y (original owner) with a 350 Cummins started over heating on inclines.  I have flushed  the radiator and put in 50/50 mix still no fix.  Someone said put auxiliary  fans?  Any help?
 

ArdraF

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I wonder if you're keeping it on cruise control when ascending and it's working so hard trying to keep up the cruise speed that it overheats.  Out here in the west we have a lot of very long gradual inclines with numerous signs about turning off air conditioners to avoid overheating.  That works with gas engines.  With both gas and diesel we've always taken it off cruise and dropped our speed some which allows the transmission to stay cooler longer.  Once you top the hill it's interesting to watch how quickly the temperatures drop when the load lessens.  There's nothing wrong with lowering your speed and thus your RPMs.

ArdraF
 

Utclmjmpr

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Speed is NEVER a factor when climbing , when you can feel an incline effecting speed, you should down shift to keep the fan speed up and at the same time it will lessen the load on the engine.>>>Dan
 

Neal

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Do you hear your fan lock in to high speed when it is getting hot?
On our 2008 Journey with normal driving we do not hear the fan, but when pulling hills (starts getting hot), we can hear it kick in.
We did have a fan clutch problem, but it was failing to come on at all, when cold. Freightliner replaced, I think the fan clutch.
My thinking is that it turns faster when needed but allowed to not turn so fast when not needed.
I know they told me it had a fuse, but if the fuse was blown, it was supposed to lock into full speed.
Just wondering if it might be failing to move into high speed.
 

ChasA

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When, under what circumstances is it overheating? What rpms showing on tachometer.
 

Gary RV_Wizard

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I'd bet that your radiator is clogged externally with oily dirt, blocking the air flow through it so that it cannot shed heat well.  It needs a good washing with a degreaser detergent and hose pressure.  Also make sure the belt for the fan is in good shape and not slippping under heavier loads. If not sure, replace the belt.

It's also possible the water pump is going bad or viscous clutch that drives the fan has degraded and not responding well to temperature changes, but I would not conclude that until the more obvious things have been ruled out.

I doubt if "maintaining rpms" is a concern with a 2009 coach. Modern engine/tranny combos do an outstanding job of managing rpms and keeping the engine in the peak horsepower band. "Lugging" a late model electronic engine isn't going to happen unless you force the transmission to do the wrong things by overriding its gear selection.

Now the gearheads in the audience are gonna scream bloody murder at me, so I'll yield the floor.  ;D
 

John Canfield

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Agree with Gary,  if your radiator has never been cleaned with heated high volume low pressure spray,  that is my first guess for your overheating problem.  Also could be the fan clutch if yours has one or a combination of both.  Flushing the radiator is a good idea but that's not the root cause of the problem.  I hope you used coolant that meets Freightliner's specs for SCAs!

For the Vectra/Horizon side radiator and a Cummins ISL, it is critically important to keep engine RPM at 2,000 when climbing long grades in hot weather.
 

Top38

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In my experience, many over heating issues are cause by a clogged radiator and or intercooler which is in front of the radiator. It's easy to see if this is the issue, lift up the bed and remove the access panel to the motor, you will be able to see a good portion of both the radiator and intercooler which a flash light, and if it's clogged with dirt you will see it! As stated above its easy to address yourself if you want, a good degreaser, I used concentrate simple green, mixed it for heavy grease, used your typical pump up pressure sprayer to coat the rad and intercooler the washed it off with a garden hose. Depending on how hard your drive the MH and the types of roads you drive on will dictate how often it needs to be done. I have also heard some have extended the crank case vent line to extend past the radiator to reduce how fast the grime builds.

If yours is clogged up, normally under light load you won't have an issue but when climbing a long hill in warmer temp's is when this issue will show up! When you pull over the temp comes right back down.
 

Top38

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Gary, I agree with you about the rpm's, although letting the engine lug up a hill will build more heat vs manually down shifting to maintain more engine rpms, it won't fix a clogged radiator issue. Power equals heat, more power, more heat so you still need to get rid of it.
 

Gary RV_Wizard

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"Lugging" is not a good thing for any number of reasons, but no modern computer-controlled drivetrain will ever "lug" under load.  The only time the engine computer allows anything that might be termed "lugging" is while trying to maintain a max economical cruising speed in overdrive, aka "economy mode".  As soon as any load is encountered, it will immediately kick out of OD and strive for power rather than economy.  Watch your tach - I'll bet the drivetrain stays either at the peak horsepower rpm or between the torque and horsepower peaks.  Theengine  ECM and tranny TCU are pre-programmed for that by the engineers who really understand such things.
 

bobmacc

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Had the same issues with my 2009 Journey 39z. Had a small rad leak and replaced the rad in 2017. In May of this year, had issues with the temp shooting up from 190 to 225 almost instantly. Had to have the fan clutch replaced as John suggested. Prior to replacing the rad,  I had it cleaned twice and both times there was minimal dirt. Runs great now with 94k miles on it. Good luck,
 
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