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Old 11-02-2015, 11:50 AM   #1
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Cooling Fan Thermo Valve

Back in June I had to have the radiator replaced, Cummins in Knoxville did the work. When I got the coach back the first thing I noticed was that the cooling fan ran at high speed as soon as I started the coach. After doing some checking one recommendation was to reverse the 2 #4 hoses to the thermo valve.

This helped as the fan would come on at low speed when I started the coach but as soon as the temp got to 180F and started to circulate coolant through the radiator the fan would come at high speed and not regulate speed as it was suppose to.

The manual says
The cooling fan speed is proportional to engine speed and radiator temperature. When radiator temperature rises above 185° F, the wax thermovalve slowly closes off the bypassing hydraulic fluid from the switching valve. A spool valve begins to move in the switching valve. This directs the pressurized hydraulic fluid to the fan motor. The higher the radiator temperature, the further the spool valve is moved in the switching valve, providing a higher volume of pressurized hydraulic fluid to the fan motor. Fan motor speed is increased to meet the demand for cooling. The action of the thermovalve is designed to move the spool in the switching valve to ramp up fan motor speed. This design saves horsepower and increases fuel mileage by precise control of hydraulic fan motor speed. The fan motor will increase in speed when the motorhome is ascending long hills or operating in high ambient temperatures. It is normal for the fan to “roar” when it is operating. Fan motor speed and engine rpm are approximately the same with the switching valve at full engagement.
The wax filled thermovalve is mounted at the top of the radiator sensing coolant temperature. The thermovalve controls the action of the switching valve. When the radiator is cool the hydraulic fluid is allowed to flow through the inlet and outlet ports of the thermovalve and return to the hydraulic reservoir. As the coolant temperature inside the radiator rises to approximately 185° the wax inside the thermovalve begins to melt and expand. This begins to restrict hydraulic fluid flow through the thermovalve. The restricted hydraulic fluid pressure then begins to move the internal spool valve of the switching valve. The process will continue until coolant temperature inside the radiator reaches approximately 199°F. At this temperature hydraulic fluid flow through the thermovalve is stopped, moving the spool valve to full open position.
At this point I do not think my system is working as designed. When Cummins reversed the hoses did they damage the thermovalve. Can it be repaired or does it have to be replaced. NW Supply does sell the thermovalve Part# B5531-09857-210 (this is off a parts list I have for my coach) for ~$450. I also found that White House Products LTD UK has this for ~$260 with exchange rate and shipping.
Anybody have success in replacing the thermovalve, is it worth the trouble. My coach now runs 180-185F never gets hotter due to the fan running full blast. The transmission actually gets hotter, up to 205F. when in the past seldom had that much of a F delta.
Any opinions on this???


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Old 11-03-2015, 08:03 AM   #2
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I guess my long post has resulted in no comments.

To be clear, has anyone had a problem with their cooling fan motor running wide open and if so what did you do to fix?
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Old 11-03-2015, 06:35 PM   #3
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I sent an inquiry to Monaco Tech Services and received an email response followed by a phone call. The tech rep said I should conduct 2 tests on the thermo valve. Plug both lines at which point the fan should run WAO and then put a union in the line and it should then run at idle. If it does this it shows that the fan motor and switch valve is operating as it should and the problem is the thermo valve.

I'll try and perform these tests in the coming days.
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Old 11-03-2015, 08:28 PM   #4
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If the fan is going to full speed 180 is what mine does. If the engine stays at 180 that what it's supposed to do. I wanted to run my engine hotter but I could only get a 180 thermostat. My valve is only a two position valve so I only get slow and fast. It would
be great to have a multi position valve so I could get the engine up to at least 200
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Old 11-03-2015, 08:36 PM   #5
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Oldguy70
What year, make, model of your coach and engine?

My fan never hardly ran before. I remember last year on a trip I pulled off the highway after a hard pull and it was still running when I walked around the rig and thought what the heck is that.

It now runs all the time. The thermo valve is suppose to regulate fluid to the switching valve which is actually what makes the fan run fast or slow.

Once I do the test that the Monaco rep told me to do I'll decide whether to order a new valve. I found a source out of the UK for ~$260.

I just want my system to work as designed.
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Old 11-03-2015, 10:49 PM   #6
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Jim, there was just a thread on this matter a short while ago but I can't find it. Seems most are going with an aftermarket valve from source engineering. My fan just started doing that for the first time this past weekend. At idle, the fan runs at full speed. It has never done that before. Looks like I need to follow along on your thread as well.
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Old 11-04-2015, 12:26 AM   #7
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try this link
http://www.irv2.com/forums/f115/hydr...=fan+runs+high
http://www.irv2.com/forums/f115/hydr...=fan+runs+high
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Old 11-04-2015, 04:23 PM   #8
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I did the tests that Monaco service rept told me to perform. I plugged both hoses and the fan ran wide open, I then plumbed both together with a union and the fan ran at idle. I emailed this info to Monaco and they said that the thermo valve is bad.

I asked if the thermo valve could have been damaged by Cummins when they crossed the hoses and they said they didn't think so.

I have to now decide if it is worth the trouble getting a new thermo valve at a cost of $260. It would take +3 years to get a payback if my fuel economy increased by 1/2 mpg.

Since the fan runs a low speed initially and then goes to full when my temp gets to 180 I wonder if it's running at optimal performance since my temps never go above 184-5 F.
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Old 11-04-2015, 04:33 PM   #9
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Old 11-05-2015, 09:24 AM   #10
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Old 11-05-2015, 09:48 AM   #11
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Jacwjames, I am not sure that you can tell by your ear what in between speed the fan is running at. Further more, if the thermovalve regulates the fan to slow when the engine is cold and fast when the engine is up over 180 degrees then my guess is that the thermovalve is working ok. The valve is wax filled and appears to be working at the full range so therefore is most likely working at the in between positions also since it is expansion and contraction of the wax. The description you gave on how it is currently working sounds just like mine. What I thought to be fast at 180+ degrees was not actually fast but an in between speed and didn't realize that until I was in West Texas in the summer and it was 110* and I pulled into a campground by Marfa and left the engine running and got out and walked around the back of the MH and the fan was roaring at a speed I had never seen or heard before. So what I am saying is there is a good possibility that what you are calling fast is a intermediate speed and you have yet to hear fast.
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Old 11-05-2015, 01:50 PM   #12
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Quote:
Originally Posted by Mike Canter View Post
Jacwjames, I am not sure that you can tell by your ear what in between speed the fan is running at. Further more, if the thermovalve regulates the fan to slow when the engine is cold and fast when the engine is up over 180 degrees then my guess is that the thermovalve is working ok. The valve is wax filled and appears to be working at the full range so therefore is most likely working at the in between positions also since it is expansion and contraction of the wax. The description you gave on how it is currently working sounds just like mine. What I thought to be fast at 180+ degrees was not actually fast but an in between speed and didn't realize that until I was in West Texas in the summer and it was 110* and I pulled into a campground by Marfa and left the engine running and got out and walked around the back of the MH and the fan was roaring at a speed I had never seen or heard before. So what I am saying is there is a good possibility that what you are calling fast is a intermediate speed and you have yet to hear fast.
I agree hard to tell without knowing the specs and the rpm its running at but as Mike has stated here, more than once I thought I had heard my fans on high, however when I headed over Wolfs Creek Pass Colorado in @ 100 temps and near the top ...those fans went full tilt boogie and sounded like a 747 taking off.
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Old 11-05-2015, 07:09 PM   #13
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Mike & Robroy,
When I bypassed the thermo valve the fan was running at the same speed when it kicks on a 180 (at least from a sound standpoint).

My fan would run at higher speed only when really hot before. I now hear it running all the time after the temp reaches 180F. It never did this before. My temp now runs at 184 climbing long steep grades. Historically it would go to 190. Something isn't right.

I've had the coach for ~7 years now and know something is different.

I've ordered a new thermo valve from White House Products LTD UK, the cost including shipping was ~$260 US. 553/1/09857/210 Thermo Valve, Wax valve
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Old 11-05-2015, 09:34 PM   #14
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On my fan the wax in the thermovalve (same thermovalve part number as yours) does not start to melt until it reaches 185 degrees and full fan speed is not reached until the thermovalve is totally shutoff at 199 degrees. This means that from initial warmup until 185 degrees the fan runs at one constant speed and will not start speeding up until the the thermovalve starts closing when the wax starts melting again at 185 degrees. So according to my manual Fan speed change will only occur between temps of 185 and 199 degrees. Now some motors have a heat sensor on the intake manifold as well as having the thermovalve and is hooked in parallel. This intake manifold sensor sends a signal to a relay in the Rear Run Box and can also make the fan speed up. My Detroit does not have that secondary system but Cummins used it on some of their motors. Also my motor has a PTO off the transmission that drives a separate hydraulic pump to run the fan and this helps to supply more hydraulic fluid to the fan especially at idle so if needed my fan can run at full speed at idle. It maybe that some engines that don't have this dedicated hydraulic pump cannot supply enough fluid to run the fan at full speed when the motor is at idle but can do it at higher motor rpms.
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