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Coolant Temp and Radiator Fan Speed


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What is considered the normal operating temp for a 2006 ISM 500 with an OAT of 70 degrees? Same for the transmission temps. Also, at what water temperature should the fan shift into high speed?     

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In my operating manual there is a good writeup about the cooling temps and what temps you should be seeing and at what speed the fan ramps up. 

In my case I believe the fan runs low speed at 185F but then starts ramping up speed with higher temps to 193F.  I rarely see temps higher then that.  Tranny temp is similar, follows the engine temp unless pulling a hard pull. 

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That's what I remember seeing on our way from AZ to WI 6 weeks ago. Today with 75 OAT, coming back from an alignment, the temp ranged between 188 and 197. On the level @ 65 mph it was 188. On a 3/4 mile incline that saw the boost go from 20 psi up to 40 psi, the temp quickly rose to 197 degrees. Then at the top, after leveling off, the temp came back to 188.  Ater topping off with fuel and a couple miles back home, the temp sits at 185. The transmission temp will stay steady between 190 and 195. I normally would not question these numbers if I hadn't seen lower values on our trip earlier. In 5 days, we will be in MT and ID with mountains instead of small hills to climb. Then I will normally down shift to maintain 1800+ rpm to help the cooling. I've read that the fan will go into high speed @ 220 degrees. Others say 195 while some say it is variable. Some say the engine will protect itself and not to worry. I just want to know what Monaco/Cummins designed the safe range to be for the ISM 500..  

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3 hours ago, Venturer said:

I suspect the ISM is higher. My ISL would switch to high speed at 212 degrees and shut off at 190.

Guess that's why I have never heard my fan run at high speed 🤔.

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26 minutes ago, 96 EVO said:

Guess that's why I have never heard my fan run at high speed 🤔.

I never heard mine until the thermovalve failed and it went to high speed.  Something sounded different so I got out and walked around the coach and it was loud. 

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Posted (edited)
18 hours ago, jacwjames said:

I never heard mine until the thermovalve failed and it went to high speed.  Something sounded different so I got out and walked around the coach and it was loud. 

When the thermovalve failed do you recall what the water temp was when the fan went to high speed? From what I can find, the valve begins to close @185 and is fully closed @199. At that time, all the hydraulic fluid is going to the fan motor. Your valve must have failed in the closed position then. I wonder if my rapid temp increase on a mild incline, is the result of the valve not closing to divert all of the fluid to the fan???  Another thought is when the thermovalve fails, does it "Always" fail in the closed position causing the fan to run at high speed? 

Edited by Venturer
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2 hours ago, Venturer said:

When the thermovalve failed do you recall what the water temp was when the fan went to high speed? From what I can find, the valve begins to close @185 and is fully closed @199. At that time, all the hydraulic fluid is going to the fan motor. Your valve must have failed in the closed position then. I wonder if my rapid temp increase on a mild incline, is the result of the valve not closing to divert all of the fluid to the fan???  Another thought is when the thermovalve fails, does it "Always" fail in the closed position causing the fan to run at high speed? 

When mine failed I pulled up the bedroom engine hatch so I could see what was going on.  At startup the fan would be at a low speed but as soon as the thermostat opened and sent hot water to the radiator the fan would go to high speed.   From memory ~175F.   Went directly to high speed, did not ramp up with temp. 

That's when I contacted Monaco Tech support, initially by email and they told me to do the two tests! 

  1. I plugged both lines and the fan ran wide open.
  2. I then put a union in between both hoses and the fan ran at an idle.

Based on that they thought the thermovalve was bad, I ended up ordering one from Whitehouse Products in the UK.

Once I got the new thermovalve installed and everything was working I decided to take the old thermovalve apart.  Ended up finding a small piece of rag in it, I had just had the radiator replaced at a Cummins shop and figured that when they removed the thermovalve and moved to the new radiator a small piece got stuck on it.  It was enough to stop the valve from opening resulting in the fan to run wide open.

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Posted (edited)

OK thanks. FWIW, I think the valve is normally open until the water temp causes the wax to melt and closing it. The piece of rag in it blocked the flow thru it simulating what a high temperature would do to the wax. That caused the flow to go through the switching valve which caused the fan to go to high speed like it would have if high water temperature had melted the wax.  At least that's my understanding of how it should work. 

Edited by Venturer
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36 minutes ago, Venturer said:

OK thanks. FWIW, I think the valve is normally open until the water temp causes the wax to melt and closing it. The piece of rag in it blocked the flow thru it simulating what a high temperature would do to the wax. That caused the flow to go through the switching valve which caused the fan to go to high speed like it would have if high water temperature had melted the wax.  At least that's my understanding of how it should work. 

The piece of rag was actually caught in the spring. 

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I'm trying to understand the thermovalve function. As the water temp increases, the wax begins to melt slowly closing the valve. My OM says it is completely closed at 199 degrees. My question is, does the fan gradually increase in speed as the wax is closing the valve, or does the fan shift to high speed when the switching valve recognizes the closed thermovalve?  

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Thanks Jim. That's what I suspected. Before I saw your response, I spoke to Scott Zimmer at Source Engineering and he confirmed that the fan motor ramps up as the thermovalve closes. He also said the 40# turbo boost would double the heat generated which could explain my temperature increase. I'll just have to watch things more closely in the mountains next week. 

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  • 2 weeks later...

We are 2/3 back to WI from our trip to ID. The water temperature has varied from 188 to 201 and the trans temp between 192 and 197. The numbers are the same whether in 70-degree temp or 92 as it is today. On the long uphill pulls, it climbs up to 200 (when the wax valve is completely open) and quickly comes back to 188-190 after leveling out. I guess it works the way it's supposed to. I'm liking this Exec more every time I get in it and the torque of the ISM still makes me 😎 pulling the hills.  540 miles today and 550 tomorrow will get us home. 

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I use a Silverleaf VMSpc to monitor the engine, one of the features is that you can set up data logging.  I was having with tranny temps and bypassed the internal radiator cooler and added a stand alone cooler with fan. 

My wife just returned from a trip and I went back and looked at the data log.  ALL good

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Posted (edited)

I really liked the VMSpc Silverleaf I had in our 2013 Bus. I would get a replacement; however, they are no longer available. So far, the Alladin system is working as it should. I'm told that the tranny mid 190 temp is not out of line, even though it ran 20 degrees cooler in our Bus.

Edited by Venturer
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I was seeing tranny temps close to 240F.  Stuck in traffic and nothing I could do about it.  

I initially installed a DeRale cooler which worked great but failed after ~1 year.  Lost 3 gallons of tranny fluid but it doesn't appear to have hurt the tranny.  I bypassed the cooler and relied on the internal radiator cooler but under the right conditions the tranny would get hot.

I've since installed a cooler normally installed on rear radiator coaches.  I did add a fan with switch.  I went back and looked at the data log temps from my wifes trip and they ran between 165-175 pulling grades. 

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I have a 2005 Monaco Dynasty with the ISL400-2 Cummins motor.  I have disabled the SD control valve and added a needle valve to get maximum flow to the pressure to the shuttle valve which control flow to the fan hydraulic motor.  The fan runs 15-20% faster than the motor RPM and was tested from idle 600 rpm to 2100 RPM giving fan speeds of 700-2600. On hot days and with higher grades such as PHX to Flagstaff I will need to pull over and the let the engine cool down from the warning light temperature of 225F.  I am unsure if the hydraulic system is working correctly but it certainly isn't ever "loud" with the SD control valve closed while idling.  I tach'ed the fan with an adjustable LED strobe light.  Does anyone know what the FAN RPM should be with the "valve" closed/disabled on the pilot side?  I suspect the radiator is the issue, but I'm curious if other sensors would turn the fan on higher if there are other controls in the system I am unaware of?  Installed: New coolant tank (tested to 16psi), new thermostat (180F) and keep the motor at 2000 rpm when climbing.  I am also looking to source a radiator as a possibility and could use some ideas.  Thanks.

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When my thermovalve failed I could hear the fan running WAO in the cab,, when I got of the coach and walked around the front the fan was screaming loud.  No way to mistake it. 

My only recommendation is to do these tests, Moncao had me do these to check the motor, there are two small lines going to the motor/switch

  1. I plugged both lines and the fan ran wide open.
  2. I then put a union in between both hoses and the fan ran at an idle.
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Hi Jim and thanks for the response!  The needle valve is connected to the hoses you are speaking of so closing that needle valve is blocking the flow and moving the shuttle via pressure to wide open for the hydraulic fan motor.  I may have to do some deeper digging on the hydraulic fan and pump if it should be running wide open at idle which makes sense to me when the condenser/CAC/or radiator are calling for cooling.  I was hoping for an RPM vs fan speed table for "that" motorhome.  it seems like it might be bypassing too early at motor idle and valve closed on pilot line conditions.  I also replaced the water pump which I forgot to mention.  The fan will speed up and make a lot of noise but the motor speed (driving the pump GPM) must be at 2100 or better to get 2600 rpm out of the fan.

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Not sure if you could get the number off you pump and motor and see if a Hydraulic shop can tell you what the specs are as to flow and pressure.  

I know it would be possible to hook a flow meter to it and see what pressure and flow you are getting, but getting a shop to do it would be another thing. 

 

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