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Old 08-20-2018, 03:18 PM   #1
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ISL 400 Overheating

I have been experiencing overheating on warm days at higher altitudes (while towing my Jeep). I am heavy at 43' with tag axle and on long climbs, I have needed to shift down and even give up speed in the selected gear at times to stay below the red. I assumed the weight (can't remember the exact number) was the reason and since downshifting solved my immediate problem, I haven't worried about it too much. But I came across a related thread on FMCA and it made me realize that just because it happens doesn't mean it's necessarily normal.

Before it gets complicated and expensive, I have done the simple things like insuring the coolant is up, replace the 13# cap, and pressure washed (without damaging any fins) through the outside of the radiator.

The fan controller could certainly be suspect but I don't know how to go test it. Is there any way for me to insure it is working as it should?
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Old 08-20-2018, 04:14 PM   #2
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Quote:
Originally Posted by StuartT View Post
I have been experiencing overheating on warm days at higher altitudes (while towing my Jeep). I am heavy at 43' with tag axle and on long climbs, I have needed to shift down and even give up speed in the selected gear at times to stay below the red. I assumed the weight (can't remember the exact number) was the reason and since downshifting solved my immediate problem, I haven't worried about it too much. But I came across a related thread on FMCA and it made me realize that just because it happens doesn't mean it's necessarily normal.

Before it gets complicated and expensive, I have done the simple things like insuring the coolant is up, replace the 13# cap, and pressure washed (without damaging any fins) through the outside of the radiator.

The fan controller could certainly be suspect but I don't know how to go test it. Is there any way for me to insure it is working as it should?
You will need to manually shift down to keep the RPM's up. My temperature will creep up to 205, but seldom goes above that even if outside temperatures are 110+, but the rpm's are up to 17-2000.
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Old 08-20-2018, 10:09 PM   #3
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I don't know if all the rigs have stacked radiators. But my diplomat does. The air to air after cooler ( cools the intake air for the motor ) is in front of engine water radiator. I had to separate the radiators to clean all the bugs and debris that had built up between the 2 radiators.
Flushing from the outside of the first radiator will not remove the stuff stuck between them. It took about an hour or less to remove all the screws and brackets and lift out the front radiator so I could clean both radiators. Took a little longer to put everything back together but it was well worth the time.
I have a 400 ISL in a 40' and pulled a 9,400.lb. F-350 diesel pickup over many steep long roads in 100 deg. plus temps. and never came close to being hot.
Maybe your radiators are not as clean as you think. Just an idea to check.
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Old 08-21-2018, 02:41 AM   #4
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Replace the thermostat. There is a newer model and if yours is the original it is not a bad investment. Drop the new one and old one in boiling water and watch how they open.
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Old 08-21-2018, 06:27 AM   #5
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Quote:
Originally Posted by flamebuster View Post
I don't know if all the rigs have stacked radiators. But my diplomat does. The air to air after cooler ( cools the intake air for the motor ) is in front of engine water radiator. I had to separate the radiators to clean all the bugs and debris that had built up between the 2 radiators.
Flushing from the outside of the first radiator will not remove the stuff stuck between them. It took about an hour or less to remove all the screws and brackets and lift out the front radiator so I could clean both radiators. Took a little longer to put everything back together but it was well worth the time.
I have a 400 ISL in a 40' and pulled a 9,400.lb. F-350 diesel pickup over many steep long roads in 100 deg. plus temps. and never came close to being hot.
Maybe your radiators are not as clean as you think. Just an idea to check.
I am confused by your post. This does not sound like a 2007 Diplomat. We have a 2006 Diplomat with the CAC stacked on top of the radiator. Either you don't have a rear radiator Monaco or you are talking about a different coach from your signature.

Bob
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Old 08-21-2018, 06:34 AM   #6
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Have had an intermittent problem with my ISL the past few years and tried cleaning the radiator last summer and had it looked at by a diesel guy with no help. They did check to fan function and it was OK. This winter I have the radiator flushed and the thermostat replaced and I have only seen it get close to the first hot mark on the gauge twice since. Other than that I swear the needle on the temp gauge is painted on. Not sure there is a magic bullet to solve this problem.
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Old 08-21-2018, 07:10 AM   #7
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I agree with Windsor Bill. When pulling a grade keep the RPM's in the 1800-2000 range by gearing down manually.
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Old 08-21-2018, 10:15 AM   #8
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I like the suggestion to upgrade the thermostat and just ordered one. Time I replaced the coolant anyway.

I note the interest in SilverLief and have an Aladdin system already which gives me an engine function display. The displayed temps are consistent with the temperature gauge (unusual, I know )

I found a partial answer to my actual question on another website. The fan should go to full speed when (1) the fan controller ground is disconnected or (2) the fan controller plug is disconnected. I not sure which answer is correct yet. I also saw a post that when started, the fan should go to full speed if the A/C is on. I went out and checked and mine does not, and that refreshed my memory that last year, when I would start the engine, I could hear the fan go hi - low - hi - low for several minutes before it would finally quit cycling up and down. Eventually it quit doing that and I forgot all about it.

In thinking more about it, I now do not believe I ever hear the fan howling on high when I am pulling a grade. Guess where I am going to focus my attention now?

Ps. Just to clarify, I have a side radiator.
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Old 08-21-2018, 11:57 AM   #9
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N is for gear selected and N gear it is in, the 60 is the cruse set speed i have selected and the large yellow circle will be green when the cruse is on , you can set up the screen any way you want. Go to the link Bob posted for more info, you can also down load the system to a laptop to play around with, its free just have to pay for the system that plugs into your coach computer.
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Old 08-21-2018, 12:37 PM   #10
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You haven't said what your temperature was. In tough hot climbs my rig will climb to 205
and then stay there. That is until last weekend when it was up there around 205 and went
to 210. When I stopped I check the fan and it wasn't running at high speed, so I will
have to find out why. The thing I noticed when I fueled up is I used less fuel. I tried to
buy 190 thermostats when I first bought my rig but I could only get 180.
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Old 08-21-2018, 02:02 PM   #11
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Quote:
Originally Posted by oldguy70 View Post
You haven't said what your temperature was. In tough hot climbs my rig will climb to 205
and then stay there. That is until last weekend when it was up there around 205 and went
to 210. When I stopped I check the fan and it wasn't running at high speed, so I will
have to find out why. The thing I noticed when I fueled up is I used less fuel. I tried to
buy 190 thermostats when I first bought my rig but I could only get 180.
Peter, I can't remember the exact temp but I am thinking it was around 220-225 and the gauge was just hitting the red line. Should have written it down.

I just went out and disconnected the fan controller and the fan speed went to high (loud). Thien I rechecked if it would come on at idle with the A/C turned on. It did not. I guess I will have to wait for our next trip, find a hill to climb and pull off when it hits the high temps and listen to the fan.
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Old 08-21-2018, 02:22 PM   #12
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I had a 2005 Imperial with the 400 and experience high temps out west too. If your fan switch is bad it will default to wide open all the time.Manual down shift was the only thing that worked for me.
Got a big Detroit now problem is gone
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Old 08-21-2018, 04:01 PM   #13
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https://www.google.com/search?q=side...earch=irv2.com

Check out some of these threads on side radiator fans. There is tons of information on that issue.
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Old 08-21-2018, 06:20 PM   #14
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Quote:
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I am confused by your post. This does not sound like a 2007 Diplomat. We have a 2006 Diplomat with the CAC stacked on top of the radiator. Either you don't have a rear radiator Monaco or you are talking about a different coach from your signature.

Bob
Bob you are correct. I had to go out and look up under the rv. and make sure. And yes the air to air is on top of the engine radiator. We have been cleaning so many radiators on tractors,semi's and pickups this year mainly due to the ash from all the wild land fires along with the usual bugs I guess I had them mixed up aprox 75 rigs makes it easier for me to lose track these days..Thanks for correcting me and sorry to the OP for bad info.. Doug.
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