Overheating on climbs

[kmb1966]

I have a 2003 Newmar Dutchstar with a CAT 3126E with a SIDE MOUNTED RADIATOR (driver side). We took unit to Eureka Springs Arkansas a few weeks ago where it is very hilly, no problems,.. all ran normal. When I got back I had the Freightliner dealer change the water pump belt in it because it was getting old. Now today I am driving down I-40 from Amarillo to Albuquerque, NM. All of a sudden the Water temp red light came on. We slowed down and light immediately went off. Pulled into rest area let engine run, and the temp quickly went down to around 182 degrees. Take off again going about 62mph in 6th gear, temp goes to 200, then 205, then 210, 215..... I slow down to 55 still climbing to 218. Going down hill it quickly recovers to around 198. On flat land it reads around 195-198. But as soon as an incline, the water temp quickly rises. dash A/C is off.
Radiator coolant is full.
Radiator cap is 13lb cap.
Hydraulic fan is running.
If I turn on the heater, the temp goes down some.
If I gear down and run higher RPM, the temp comes down some (But I have never had to do this before, so I suspect something is wrong).
Does not heat up sitting idle with a/c ON.
Not sure what to do. Resting at the RV park but not sure if I can go any further.

[Hoosier14]

It seems the main clue is performance before and after you had the belt replaced. If the belt is too big or not adjusted properly it could be slipping. It might be operating enough for water to circulate to cool in low power situations, but not enough when you are pulling hard.

[VanDiemen23]

Check the belt, but it's not completely abnormal behavior. Have you driven the american west much before? The temps are higher, the grades are longer. Gear down, slow down on long grades. Drive the temp gage, not the speedo.

I have a 25 gallon ag sprayer to douse the radiator on long grades, that helps too.

[kmb1966]

Does anyone know how much "play" is supposed to be on the water pump belt??

[caninecop]

I have the cat 3126E 330 hp, if I keep the RPM's just over 2,000 the temp stays around 198-200 on my scangauge D. If you haven't done it yet do a search on the board for overheating, you will get a lot of info on how to help keep the overheating down.

[JaminSamin]

Originally Posted by kmb1966

Does anyone know how much "play" is supposed to be on the water pump belt??

Caterpillar says deflection of 0.35 to 0.59 of an inch is good for the 3126E.

[Skip426]

Two things to mention here .

1 . Your engine has two thermostats for coolant circulation ( both in the same housing at the upper rad hose ) if one is opening correctly , the engine will cool when not under load , both need to open to keep the engine cool under load.
2. The hydraulic rad fan controller , has to operate properly to cool the engine under load, just because you can see the fan turning doesn't mean the system is operating properly . Contact the Freightliner free help line with your chassis serial number for testing info on your rad fan controller . I kow how to test mine but , my chassis is 4 years older.

Note : The controllers ; in failure mode ; should default to max cooling fan RPM ; I've had two controllers fail , and both times the rad fan was stuck in minimum RPM mode , causing a quick overheat condition.

Freightliner Help

1-800-FTL-HELP
1-800-385-4357

[kmb1966]

Update on this topic:
Changed the Radiator Cap. The center portion of the cap was very loose and the outer gasket was dry rotted. After changing the cap, it seems to run much cooler. Downshifting and slowing down to 55 or less on long climbs seems to make the engine water temp go down significantly. I'm not sure why that's the case other than it is spinning the water pump faster and therefore moving more coolant through the system.
Trip from Albuquerque to Flagstaff temps ranged from 188-203F (highest) Outside temp was very cool (70F)

[boyland]

This is an interesting topic i would like to add some things:
How are you reading the temp I have a scan gauge D unit and on the dash it has an analog like temp without actual temp marks just range from cold to all the way over in the red.

I have run years without the scan gauge and watch the temp climb on the dash but never reach the red area or result in loss of power. It would usually just get above middle on climbs and i can only think of one time where it actually went any higher than that.

Since i had the scan gauge it gives me a number i am not really sure where it reads the temp exactly from but i will say it always tells me the engine is much hotter than i really think it is. In the middle of the analog gauge it will reflect 200-205. But i can touch the water hoses lines and i can tell you that water is no were near 200 degrees. It will also rapidly reduce like seconds after i let off.

I more suspect the water temp for it is on the outlet of the motor so it is what is being returned to cool but idk.

Always been curious about that since i had the scan gauge

[kmb1966]

I have been watching the analog reading and my scangauge-D water temp reading. Both seem to be reading the same value. Red warning water temp light comes on at around 220F.

[CountryB]

Originally Posted by boyland

Since i had the scan gauge it gives me a number i am not really sure where it reads the temp exactly from but i will say it always tells me the engine is much hotter than i really think it is. In the middle of the analog gauge it will reflect 200-205. But i can touch the water hoses lines and i can tell you that water is no were near 200 degrees. It will also rapidly reduce like seconds after i let off.

I more suspect the water temp for it is on the outlet of the motor so it is what is being returned to cool but idk.

Always been curious about that since i had the scan gauge

The Scan Gauge gets its informant from the ECM data - so the tempera sensor is the same one the engine computer uses (usually installed in the block or head).

The dash gauges get their readings from a different sensor installed by the coach manufacturer (usually located in the thermostat housing or upper radiator hose)

[boyland]

Good info, I have always wondered when it would tell me it is too hot fortunately i have never hit 220 i guess

[Gaspumpcity]

2003 M/H ? Have you ever had the radiator checked for partial plugging on inside? By you changing the radiator cap was a start! Start checking easy stuff first like water pump pressure (this will eliminate belt issues. Is your engine turned up number one cause ( not enough radiator) oh forgot to ask is front on radiator and condenser bugged up ? Is the M/H overloaded? Trying a known temperature gauge for accuracy! Do you know how much boost (PSI) your making? All of these checks are basic troubleshooting my guess year 2003 has it ever been changed?

[Gaspumpcity]

If you have low boost your fins on the exhaust side could be damaged another quick check but you would have low power which you didn’t mention