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Cummins ISL Radiator Fan Won’t Increase Speed

June 11, 2022, 05:40:15 pm

Hi All -

Sorry if this has been posted before, but we are hot and tired and I couldn't find any mention of this. We have a 2002 U295 with the Cummins ISL 400 (side radiator). Our engine temp will creep up and up until we have to stop to let it cool. We have figured out that the hydraulic radiator fan is not increasing its speed as it should. We will get out and the fan will be on an idle type speed. We talked to MOT tech support and they had us unplug a cable from the gray hydraulic box located right above the frame in the engine bay. It should have caused that fan to kick on high, but it didn't. We want to just get it to run high until we get back home to Colorado. Anyone ever experienced this? If so, do you have a work around to get the fan to kick on full blast?

Thanks!

Cory

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Re: Cummins ISL Radiator Fan Won’t Increase Speed

Reply #1 – June 11, 2022, 06:04:08 pm

Cory,

Have you verified the fluid level in your hydraulic tank?

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Reply #2 – June 11, 2022, 07:10:53 pm

Hi Brett -

Thanks for the reply! We just had it serviced and all fluids checked, but I suppose we need to look for ourselves. This is our first big journey so we are still learning. I believe that is the black cylindrical container in the rear engine bay, correct? Is there a good way to check the levels?

Sorry for the rookie questions, but my brain is struggling today.

Thanks!

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Re: Cummins ISL Radiator Fan Won’t Increase Speed

Reply #3 – June 11, 2022, 07:55:36 pm

Im assuming your steering is fine so fluid level should be okay. Remove the plug on your electronic fan controller and fan will go to hi speed if the controller solenoid is still working, if not you will need to restrict IE shut off the fluid flow threw the controller. I actually left a needle valve inline to manually adjust fans speed in case of a failure. #4 or a #5 line. The restriction causes the fans to ramp up to hi speed.
Scott
This was my final resolution
Hydraulic fan controller DIY
Ref
Hydraulic fan controller
Photos
Radiator and fan motor
Cleaning plug
Radiator and fan motor

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Reply #4 – June 11, 2022, 10:19:49 pm

Thank you! This is great information! We have so much to learn. In he short term, since we were mid-trip, we checked all of the connections in the engine bay (disconnected/reconnected several to ensure a good connection). Not sure if that helped, but from that point on the temp gauge hovered around 185. It was like a miracle. I'm hoping the gauge wasn't showing false readings, but when we did park up tonight at a campground the engine seemed fairly cool. Well, cool for driving 8 hours in 100 degree weather.

Anyway, will see how it goes tomorrow and will look into your fix when we get back to Colorado!! Thanks again!!

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Re: Cummins ISL Radiator Fan Won’t Increase Speed

Reply #5 – June 13, 2022, 10:44:04 pm

I had a creepy gauge and I eventually discovered it was the gauge wiring at the gauge. Use a hand held ir temp gun and check the temperature at your thermostat housing and then compare to gauge. Hit the gauge with your knuckles a few times to see if it drops down. Several of us have gone through this wild goose chase.

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Re: Cummins ISL Radiator Fan Won’t Increase Speed

Reply #6 – June 14, 2022, 09:39:07 pm

Cory, on my 2002 U295 I've not yet been happy with how hot it runs. PO said he had replaced the radiator. I've been chasing this for awhile now. When you disconnect the controller module from the fan motors the engine has to be in high idle, cruise control buttons or the fans won't go to high at idle speed.  I've followed DSD's lead and installed a wax valve, I left old controller as is and can reinstall hoses if I want to go back if desired. I also installed an electrical hydraulic shut off valve in the small hose to the fans. Used one of the extra wires running back to the dash and installed a switch in one of the blank holes on the dash. This way I can run the fans any time I want on demand. Don't want to guess how the fans are functioning. I have not yet tested it yet to see if I can lower my coolant temp on hills yet. I will post when I do. I partially have come to the conclusion this coach just  does not like the Southwest. Jim.       

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Re: Cummins ISL Radiator Fan Won’t Increase Speed

Reply #7 – June 14, 2022, 10:22:51 pm

Don't forget to keep your revs up. Last summer I was going up a slight grade a the engine
was pulling at 1200 RPM and the temperature had climbed to 200 degrees. I shifted down
and the temperature just dropped. The fan was still running at low speed.

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Reply #8 – June 19, 2022, 10:00:03 pm

Thank you all for your responses. Such a stressful thing to go through when you're driving through Texas and Oklahoma on a 100+ degree day! And especially on a weekend when nobody is open. Luckily, our playing around with the connections in the engine bay seemed to do something and our temp stayed around 185/190 the entire way back to Colorado.

I like your solution Jim. I hated guessing what my fan was doing and would have been nice to just force it into high mode. We are taking it for emissions testing this week and the guy also happens to be a diesel whiz, so am going to chat with him about some options as we have another big trip mid-July.

I appreciate the advice Peter. We did try downshifting when the revs were low, but it didn't do anything for the temp. So that could mean a bad gauge. So definitely need to test the actual temp vs what the gauge says.

Thanks all!

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Reply #9 – June 19, 2022, 10:26:40 pm

I know the gauge on my dash reads really high so I have a new sensor that I'm putting in but
as I have a Silverleaf I know the temperature is fine. I don't know about your year of coach
if you stop the oil from flowing though though those small lines going though your fan
thermostat the fans will go into high gear. I followed Scott idea and put a n/o solenoid valve
in those lines so I can manually put my fans in high gear any time I want to. Also if you have a
inferred thermostat check the engine temperature with that.

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Re: Cummins ISL Radiator Fan Won’t Increase Speed

Reply #10 – June 21, 2022, 02:58:32 pm

My dash gauge reads 210-15. Silverleaf reads 180. Rear tank air gauge just replaced and reads 145 pressure at tank 125. Don't trust my gauges but do trust my silverleaf

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