Engine Temperature Fluctuation - Concern or Not?

[fagnaml]

This past weekend (10/5-7/19) in Baton Rouge for the LSU - Utah State game was brutally hot for the first weekend of October  - 97 F ambient temperature with 105 F heat index !!   While driving from Baton Rouge to Houston yesterday (Sunday), the engine temperature was fluctuating from 192 F to 210.   I saw this fluctuation only because I had my dashboard read-out looking at engine and transmission temps rather than my customary trip and leg fuel mileage read-outs.   As I paid closer attention to the engine temp, when the temp reached 210 F I could hear (I think) the radiator fan engage / go into a higher speed and then disengage/slow down when the temp reached 192 F.   This fluctuation was continuous during the five hour drive.   I don't know if this temperature fluctuation was occurring on my drive to Baton Rouge Friday because my focus was on horrible traffic conditions and I didn't have the dash board read-out set to temperatures.   Engine RPM did not change (stayed at 1800) as the engine temp fluctuated and the fan engaged/disengaged.  Speed control was steady at 65 mph (my comfortable max speed).     This weekend was the first time driving my new to me Newmar Ventana LE in extremely hot weather.

Is this 18 F temperature fluctuation "normal" or is it the sign of a problem brewing?  Thanks for the help!

[rossboyer]

While we can only guess because we don’t know what engine, chassis and year and model, I think that that swing is reasonable. From your description, looks as though the fan and thermostat are working well. Just the fact that the temperature does come down indicates to me that the cooling system is working as it should. 

[wolfe10]

Contact your chassis builder for their spec on delta between thermostat fully open and cut in temperature for fans to HIGH.

18 degrees sounds high to me, but you DO want some delta.  If insufficient delta, you are paying HP and MPG to run fans on high more than necessary.

Also, ask them for details on the controller for fan speed-- it is possible that it is adjustable.  Ideal delta IMO would be around 10 degrees F.

[fagnaml]

Ross --

Sorry, I should have provided chassis and engine info for my 2016 Ventana LE 4037 (which should be visible in my signature block).   The chassis is a Freightliner XCR with a 6.7L, 360 HP Cummins ISB engine and Allison MH3000 transmission.   The coolant is "original fill" Shell Rotella Fully Formulated with SCAs (purple color coolant) which, per test strips, was in good condition when I purchased the motorhome six months ago.   Here is a link to coolant info --> http://shop.sclubricants.com/rotella-fully-formulated-antifreeze-5050

I don't recall seeing this engine temperature fluctuation while driving my previous motorhome unless while climbing a hill or large bridge.  The engine temp fluctuation I experienced yesterday is on I-10 which except for a few bridges is very flat.

[wolfe10]

OK with that info:

https://cdn.fccchq.com/specsheets/2016-Newmar-Ventana.pdf

 

1335 cubic-in, rear-mounted radiatorRemote-mounted water to oil Belt-driven with viscous fan clutch.

 

So, the question I would ask is what input is there that engages the viscous hub fan to HIGH?  Is 18 degrees F acceptable or would I be better off with a10 degree delta between thermostat fully open and fan to high?

[elkhartjim]

Determine from Cummins or Freightliner if you have the Horton fan Clutch. If so, this component is problematic. I replaced the Horton Clutch on my previous motorhome with a 350 HP ISB twice in 60,000 miles. First time was first year of ownership with less than 15,000 miles and again at 40,000 and was showing signs of same problem when I sold it at 60,000 miles. 

[fagnaml]

Jim --

Please share the "symptoms" you experienced with your Horton fan clutch so I can compare/contrast my experiences from yesterday.

[elkhartjim]

Same thing you're experiencing, temperature fluctuations of 15-20 ℉  towing on level surface. First repair under warranty by the Bryan/College Station Freightliner. They used the wrong grade bolts doing the repair and by the Grace of God I was within 18 miles of the Gaffney Service Center when they sheared and the fan became wedged in the shroud.  Freightliner towed me to the repair center in Gaffney and replaced. I was back there for my annual service several miles and years later when they had to replace it again. Freightliner installs the clutch, not Cummins I believe. 

2008 Fleetwood Bounder 350 ISB. Check with the Freightliner 24/7 help desk and see if your year still uses the same clutch.

[fagnaml]

Brett --

As always your advice is most welcome.   Using the link you provided I found the FCCC spec sheet for the Ventana LE which is essentially the same as the Ventana info you provided --> https://www.fcccrv.com/wp-content/uploads/oem_pdfs/Newmar/2016 Newmar Ventana LE Spec Sheet.pdf

I failed to mention in my original post that as I do every LSU football weekend I was towing my 2016 Jeep Wrangler Unlimited Sahara.

I called the FCCC "24/7 Direct" customer service phone number and was promptly routed to a technician by the name of Chris.  I explained my experiences to Chris (who sounded older in age and quite experienced) who advised the cooling system for my Ventana LE was performing as it should with the fan moving to high speed at 210 - 212 F and returning to low speed at 190-192 F and repeating the cycle as needed.  Chris said FCCC has received numerous calls about this temperature fluctuation for Ventana LE's the last few years.  Whether he should have or not, Chris stated that his personal opinion is the 360 HP, 6.7L ISB engine is somewhat undersized for my Ventana LE 4037 model especially during hot weather and climbing long hills.  He said Newmar / FCCC agreed on using the ISB engine instead of a larger engine to help hold the cost differential between the "entry level" Ventana LE and the "next step up" Ventana.   

My 2016 Ventana LE has an empty weight of 29,700 lbs, max GVWR of 36,400 lbs. and a max GCWR of 41,400 lbs -->  https://library.rvusa.com/brochure/2016VentanaLEBrochure.pdf

For an LSU weekend, I carry a full tank of water (830 lbs), full 32 gallon propane tank (135 lbs), three plastic tables, umbrella type camping chairs, small charcoal grill, food, drinks, ice, the wife & me.  All that "stuff" is under 2,000 lbs. thus well within the 6,700 lbs of "rated" cargo capacity.   Combined weight (calculated) is ~35,700 lbs. which is 5,700 lbs. under the GCWR.  Next trip I will have the coach and Jeep weighed to confirm my calculated combined weight.

Presuming the combined weight is circa 36,000 lbs. would you agree with Chris at FCCC that a 360 HP ISB engine is a bit undersized?

 

[wolfe10]

Yes, it us undersized for your weight when compared with other current generation DP's. But, the 6.7 Cummins B with Allison 3000 transmission is a pretty bomb-proof drive train.

 

Counterpoint: Dianne and I put over 150,000 miles on a 250 HP Caterpillar 3116 in our 36' Foretravel all over North America including some outrageous mountain driving in central Mexico-- no complaints.

And, particularly on flat roads (Houston to Baton Rouge) engine size is not that relevant.

I don' have specific specs for total wheel demand HP  for 36,000 pounds, but here are the numbers for 60 MPH

30,000 GCW  126 HP

40,000 GCW 134 HP

So on flat ground you are NOT stressing your drive train.

I would still ask what triggers high fan speed-- it may very well be off an engine output and may be adjustable.  18 degrees delta is more than I would like to see on my coach.

[sstgermain]

I see the exact same temps in my Winnebago with the same engine setup.

[Lenp]

Mine is a bit older and heavier and has an ISL 8.9 370hp.  The thermostat is a 160 degree and it runs pretty close to that until I start climbing and gradually increases to 210-212 where the fan kicks in and drops it back to about 195 pretty quickly.  So about a 15 degree swing.  Goes back to 160 soon after the top of the hill.

Usually easy to keep the temp under 200 by dropping a gear so seldom have the fan kick in.

I have ran that stretch of I-10 many times but with temp 10-15 degrees lower.  Never saw the temp vary from the above 160. 

Lenp

[wolfe10]

Lenp,

Wow, 160 sounds cold for an ISL.  Might want to confirm that with Cummins for your engine serial number.

[hermanmullins]

Agree, my 400 ISL runs at a constant 180. Up a grade maybe 190 and down 178. When in the mountains and going up steep grades I will down shift one gear to keep the fan on high.

By the way, I now have a new water pump and am full of ELC coolant. Well road test it in a couple of weeks. Going to Shreveport to volunteer at the Fair. 

Herman

[jleamont]

5 minutes ago, hermanmullins said:

I now have a new water pump

That made ours run cooler with the new design. Steady 180 now, pulling hills  loaded with toad 190. Only in stop and go traffic will it climb slightly above 190. 

14 minutes ago, wolfe10 said:

Wow, 160 sounds cold for an ISL. 

Does sound cold, ours has a 180 degree thermostat.

[fagnaml]

As usual the responses are very informative!!  The "thermostat responses" make me question the type of thermostat I have in my ISB engine.  I'd presume a 180 - 190 F thermostat??

Presuming I have a 180-190 F thermostat I then wonder why, if the thermostat is wide open, did the engine temp climb to 210 F driving on a flat I-10 between Baton Rouge and Houston and the fan had to go into high speed to keep cool off the engine??  

Jim S. --

What other "symptoms" did you have (in addition to the low to high temperature fluctuations that I have) to prompt your clutch replacements? . Reason for asking is my experience with "high school era" older pickups was a clutch replacement was needed because the fan would not engage and the engine overheated (those clutches were the thermal spring type that when they failed the clutch would not grab the engine shaft).  Also, the FCCC tech I spoke to yesterday told me I have a Horton brand clutch.

Brett --

You very often coach all of us to check that the charge air cooler is clean.  When I purchased my Ventana LE from NIRV in Dallas this past April I asked them if the charge air cooler needed cleaning -- they said no.   If the charge air cooler is dirty, could that be a reason the engine temperature will not hold at ~190 F with a wide open thermostat?

I have another LSU football adventure in Baton Rouge this coming weekend (10/11-13/19) with #7 Florida visiting # 5 LSU.  It will be interesting to see what my engine temps do with 75 F ambient temps behind a much welcomed cold front.

 

 

[wolfe10]

1 hour ago, fagnaml said:

Brett --

You very often coach all of us to check that the charge air cooler is clean.  When I purchased my Ventana LE from NIRV in Dallas this past April I asked them if the charge air cooler needed cleaning -- they said no.   If the charge air cooler is dirty, could that be a reason the engine temperature will not hold at ~190 F with a wide open thermostat?

ABSOLUTELY!

Get a strong flash light and access the top of the engine (bedroom or closet).  Shine the flashlight past the fan blades/inside the fan shroud. Loot at the perimeter, not in the center  (the fan blades sling the debris to the perimeter.

Let us know what you find.

In most cases the FRONT of the CAC needs to be cleaned annually.  A garden hose nozzle and  Simple Green EXTREME (aluminum friendly) works well.

BTW, sent you an e-mail with picture of clogged CAC that owner though was clean because he was only able to see the center.

 

[Lenp]

Brett, 

I thought the same soon after I bought the coach and asked Cummins and they confirmed 160 was correct.  Have thought about changing to 180 to see if fuel economy improved but have never got around to it.  Don't fix it if it ain't broke?

Lenp

[manholt]

Brett, can you post that CAC picture here?  Or PM me?

[wolfe10]

As I mentioned, if one looks just in the center of the fan shroud from above (easy as that is where the fan blades are narrowest) it looks clean.

Again, this is the FRONT (front of coach) side of the CAC (Charge Air Cooler).  It "filters" the debris sucked up by the fan.  So, cleaning from the back (back of the RADIATOR) is not very effective at removing debris from the front of the CAC.  To clean this off the front of the CAC from the back of the coach, pressure washer/steam cleaner would have to have enough PSI to go through the radiator, air gap and CAC and still have enough force to knock the stuck on dirt from the front of the CAC.  That PSI would likely bend the fins on the radiator!

When they get this bad, it requires pulling the radiator and CAC to clean.

Annual cleaning is necessary to avoid this expensive repair.

 

 

[fagnaml]

As a follow-up to my original post, below is the e-mail response from FCCC Customer Service about my engine cooling system operating "normally".    Also, last week I looked at my charge air cooler following Brett's guidance and found it to look almost new for what I could see without removing the fan shroud (I couldn't quite see the furthest corners of the CAC).   I've attached a photo of the charge air cooler (as best that could be laying under the fan and without removing the shroud).

Basically what I think I've learned is FCCC designed the cooling system to include a variable speed fan and that my 20-25 F of engine temperature fluctuation is "per design".   The FCCC website briefly describes the "automatic variable speed fan" for rear mounted radiators on XCR chassis such as mine  --> https://www.fcccrv.com/chassis/xc/engines/#xc-cummins-engines

Any comments from the forum about what I've learned in the last week?

============================================================================

Mike,

What you have described is normal operation of the cooling system. 

Sincerely,

Justin Pope

FCCC Representative

---------------------------------------------------------------------------------------------------------------------------------------

2019-10-14 12:35:45 Fagnant, Michael L.

I have a “new to me” 2016 Newmar Ventana LE (VIN# 4UZACHDT8GCHJ1970) that I’ve enjoyed the last two weekends for LSU football outings.   It is built on an XCR chassis.  The coach is equipped with a 360 HP Cummins 6.7L ISB engine and Allison 3000MH transmission.   While driving the motorhome round trip between Houston and Baton Rouge both weekends, the engine temperature would continually fluctuate from ~187 F to ~210 F despite a 20 F difference in ambient air temperature (95 F two weeks ago, 75 F this past weekend).     As the engine temperature reached ~210 F, I could hear the cooling fan “kick into” high speed.   When the engine temperature cooled off to ~187 F and the fan went to a low speed.    The engine temperature would then rise during the next few minutes until reaching ~210 F again at which time the fan went into high speed.   This temperature fluctuation cycle continued constantly.

 Prior to owning this Newmar Ventana LE, I owned a 2007 Damon Astoria that, like the Ventana, was built on an XCR chassis.   The Astoria was a somewhat smaller motorhome and thus was equipped with a 300 HP Cummins 5.9L ISB engine and Allison 2500MH transmission.   While driving the Astoria to/from Baton Rouge for the last five years, the engine temperature held constant at ~195 F.   It didn’t have the large 20 – 25 F temperature fluctuation that I’m experiencing with the Ventana LE.  

 Is the 20-25 F engine temperature fluctuation experienced the last two weekends “normal operation” or do I have a cooling system problem such as a bad thermostat?    Should the engine temperature be relatively constant as was my experience with the 2007 Damon Astoria?

Thanks for your help and advice.

 Mike Fagnant

 

 

[wolfe10]

So it is  a VARIABLE SPEED, not LOW/HIGH SPEED fan clutch?

 

Have seem that with hydraulic side radiator, but not rear radiator configurations.

If you would, please post the brand/model of the fan clutch on your coach. Inquiring minds want to know.

[fagnaml]

Brett --

FCCC told me I have a Horton fan clutch.  Which model number they did not say and silly me did not ask.  I will quiz FCCC about clutch model number.

Any comments about the photo of my charge air cooler?

[wolfe10]

Mike,

Looks like the picture is of the center of the CAC.  It will be clean, even if the rest is clogged-- see the picture I posted above.

The most likely place for it to be clogged (and also one of the harder to get a good look at is the lower perimeter.

[wildebill308]

7 hours ago, fagnaml said:

Any comments about the photo of my charge air cooler?

Like Brett said the outer/lower areas are more subject to getting dirty and clogging/restricting air flow. Personality that is so clean (where I can see it) it looks brand new. Let's hope the rest is as clean. Did you look at the front of the radiator?

I did hear of someone who had a overheating problem and found a bunch of fiberglass insulation sucked up between the CAC and Radiator. I would think a cheap endoscope like this one would be handey.

https://www.amazon.com/Seesi-Endoscope-Waterproof-Inspection-Semi-Rigid/dp/B07PBF6DX5/ref=asc_df_B07PBF6DX5/?tag=hyprod-20&linkCode=df0&hvadid=343454787283&hvpos=1o1&hvnetw=g&hvrand=7331942529068521538&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=&hvtargid=pla-781022053882&psc=1&tag=&ref=&adgrpid=68626770665&hvpone=&hvptwo=&hvadid=343454787283&hvpos=1o1&hvnetw=g&hvrand=7331942529068521538&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=&hvtargid=pla-781022053882

Bill