Coolant Temp and Radiator Fan Speed

[Venturer]

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?     

[timaz996]

I don't have your engine but my wax valve has the fan at high speed at 195.

[Venturer]

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

[jacwjames]

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. 

[Venturer]

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..  

[96 EVO]

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 🤔.

[jacwjames]

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. 

[Venturer]

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 Wednesday at 04:09 PM by Venturer

[jacwjames]

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.

[Venturer]

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 Thursday at 01:00 PM by Venturer

[jacwjames]

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. 

[Venturer]

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?  

[jacwjames]

It is suppose to gradually ramp up speed. 

 

[Venturer]

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.