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M11 Celect Plus Coolant Temp on Grades

August 15, 2017, 01:47:12 am

1998 U-320 with Cummins M11 Celect Plus 450 HP engine.

Is 200 degrees F an acceptable high end engine coolant temperature to run at for an extended period when pulling mountain grades?

When running down typical interstates at 65-70 MPH, the coolant temp is between 180-183 degrees depending on ambient air temp, grades, and speed.  I only have analog gauges and no Silverleaf, etc, so can't provide more specific temperature information.

I am wondering because we were at about 7,000 ft and hit a grade.  I wasn't paying attention to the engine coolant gauge and kept the posted speed limit.  The engine coolant temperature hit 200 degrees and seemed to hold.  No warning lights came on, but I wasn't comfortable with this when I saw it since it was higher than I've run.  I downshifted to increase the RPMs, stayed in the slow lane, and let the speed drop so that we chugged up the grade slowly.  Engine coolant temp dropped down to normal 180 degree range after a bit.

The Cummin's Operation and Maintenance book says the standard modulated thermostat range is 180-200 degrees F.  And the maximum allowable is 212 degrees F.  Since the coolant temperature did not climb beyond 200 degrees it appears our engine's cooling system is working well and working within the specs.

Does this mean that 200 degrees is an acceptable temperature to run at for an extended period when climbing grades?

Thank you for your input.

Chris

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Re: M11 Celect Plus Coolant Temp on Grades

Reply #1 – August 15, 2017, 02:19:02 am

Yup, 200 to 205 is ok, anything higher I would do as you did and gear down.

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Re: M11 Celect Plus Coolant Temp on Grades

Reply #2 – August 15, 2017, 08:15:52 am

I would strongly encourage you to get Silverleaf for more accurate readings.

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Re: M11 Celect Plus Coolant Temp on Grades

Reply #3 – August 15, 2017, 08:45:37 am

Yes, you are fine.  I run at 200 degrees regularly in mountain climbing.

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Re: M11 Celect Plus Coolant Temp on Grades

Reply #4 – August 15, 2017, 09:52:25 am

Your temp seems fine. As others have said Silverleaf is much more accurate than your gauges. My guages are more than 10 degrees off to the high side. When you turn the headlights on they are worse.

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Re: M11 Celect Plus Coolant Temp on Grades

Reply #5 – August 15, 2017, 10:20:55 am

Silverleaf is an excellent choice.  As is Scan Gauge D for under $170.

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Re: M11 Celect Plus Coolant Temp on Grades

Reply #6 – August 15, 2017, 10:52:47 am

Thank you all for the replies.

Brett - thank you for mentioning Scan Gauge D.

Chris

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Re: M11 Celect Plus Coolant Temp on Grades

Reply #7 – August 15, 2017, 11:27:47 am

Mine hit 220 up the grade from Las Vegas to Los Angeles just after state line on the silverleaf .  Mountain pass.

Engine shutdown buzzer and light came as i crested the hill at the same time and the buzzer and light both went off after maybe a total of 30 seconds.

On your motor there is a sensor on the block to control thermostatic fans in a truck behind a front radiator.

Does not turn on till 210 F,

Thermostat does not open fully to 195.

Dash analog gauge on ours is higher than the silvetleaf by quite a bit.

Allison using retarder buzzer comes on at 250 turns off when temp drops to 240.

Retarder sheds load at 300.

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Reply #8 – August 15, 2017, 11:43:15 am

I also limit the engine to 200 degrees on grades and gear down as necessary to make sure it does not exceed it. I think this is fine for long pulls. It's quite a way from the DDEC engine shutdown but since Detroits and most Cummins have wet liners, it's good to be conservative and make sure the sealing rings are protected. Since we don't have a load of fish in a refer trailer behind us, who is in a hurry?

As soon as we hit the downgrade or flat, the temp drops to 180.

Pierce

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Re: M11 Celect Plus Coolant Temp on Grades

Reply #9 – August 15, 2017, 12:27:36 pm

I also have the Silverleaf system and live in the mountains so I change down and run it gently although I keep the speed up close to 60/65.  My temps get up to 198 and I saw 202 a little while ago with very high OAT.
Speedbird 1.

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Re: M11 Celect Plus Coolant Temp on Grades

Reply #10 – August 15, 2017, 12:45:54 pm

At 100F, climbing a 10% grade, third gear at 38 mph, Engine coolant hit 205F on Silverleaf, dash gauge was higher.
I was surprised that the temperature did not get higher under those extremes.

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Re: M11 Celect Plus Coolant Temp on Grades

Reply #11 – August 15, 2017, 04:32:56 pm

High altitude and hot temps will stress a coach. I hit 210 at the top of Eisenhower Tunnel with outside temps at 99.  I geared down and was pulling a grand Cherokee and a 42 foot double slide coach. The 36 foot pulling the wrangler was 10k lighter and never broke 200.

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Reply #12 – August 15, 2017, 06:29:54 pm

My 219/220 silverleaf temp was floored full revs in fourth up mountain pass grade out of Vegas at 55-58 mph. 

Dash said around 230.

Different sensor locations on the engine for the dash gauge versus the silverleaf running off the ECM for the engine

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