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Old 07-30-2017, 02:56 PM   #1
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1991 25' Airstream 250
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Beau temps

Our coach is running a little hotter than normal, something has changed because it's been pretty rock solid at 195 over the past ten years. I noticed that the large electric fan on the front of the radiator didn't seem to be turning. I wasn't sure whether it is meant to be permanently on or whether it is driven by the thermostat or another system.

Can anyone clarify how that fan works and would I be better to actually put it onto a dash switch?

thanks
Nick
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Old 07-30-2017, 05:53 PM   #2
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1974 20' Argosy 20
Richmond , Kentucky
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Originally Posted by Boom Sounds View Post
Our coach is running a little hotter than normal, something has changed because it's been pretty rock solid at 195 over the past ten years. I noticed that the large electric fan on the front of the radiator didn't seem to be turning. I wasn't sure whether it is meant to be permanently on or whether it is driven by the thermostat or another system.

Can anyone clarify how that fan works and would I be better to actually put it onto a dash switch?

thanks
Nick
Nick, I know you've had a bunch of work done to it lately. Did any of the work involve the cooling system?

I could be wrong but I was thinking the electric fan might only be expected to run when you have the dash AC turned on. At least some systems work that way.

Brad
PS, glad you found the AC bracket
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Old 07-31-2017, 12:02 AM   #3
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Yeah, lots done but I didn't switch out the water pump (a possible culprit) or the thermostat. I've run out of time before we go away, so thought the fan might be an option. I'll take a look what happens when I switch the dash air on. Thanks for the tip.

On the thermostat, is there a consensus view on whether it is better to shoot for the 180 or the 195 version?

Thanks muchly

Nick
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Old 07-31-2017, 05:47 AM   #4
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Originally Posted by Boom Sounds View Post
Yeah, lots done but I didn't switch out the water pump (a possible culprit) or the thermostat. I've run out of time before we go away, so thought the fan might be an option. I'll take a look what happens when I switch the dash air on. Thanks for the tip.
I would think the water pump would be a cooling or not cooling type of problem. A water pump that leaks a little bit shouldn't impact cooling unless you've lost a lot of coolant. At least that's that's my take on the subject.

Quote:
On the thermostat, is there a consensus view on whether it is better to shoot for the 180 or the 195 version?

Thanks muchly

Nick
On TBI controlled vehicles the computer is expecting a certain coolant temperature and if it doesn't see that temperature it will make air/fuel/timing adjustments to try and reach the desired temperature. Based on that I would say you should install the thermostat that is spec'd for your vehicle.

On my TBI build I had the tuner set my system to use a 180 degree thermostat.

Brad
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Old 07-31-2017, 06:04 AM   #5
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I'm not losing fluid, at least very little, if at all. My simple brain says that is likely to be one of the following:

Failing water pump
Failing thermostat
Failing fan clutch (replaced about 5 years ago with a Delco and kicks in full throttle at 205 ish and rapidly cools it down. I think it is working OK)
Blockage somewhere in pipes restricting water flow and therefore cooling
Failing radiator

Does anyone know if I have missed anything obvious?

thanks all
Nick
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Old 07-31-2017, 06:42 AM   #6
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Some years ago I had and was restoring an older Mercedes car. I rebuilt the engine and in my manuals MB recommended after 5 yrs. to replace the water pump. Their logic was that in that time the vanes on the pump would have been worn down and have lost SOME of their efficiency to move water and that to maintain cooling to original specs, replace it. Most of us wouldn't think in those terms and simply don't replace them until they fail by leaking. I actually had one completely fracture the housing and destroy my radiator. But that's another story.

So, it could be a failing but functioning water pump if nothing else more obvious is established.
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Old 08-01-2017, 04:02 PM   #7
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You could use a IR thermometer and read the radiator in various spots to try and find hot and cool spots while the engine is running and up to temp. That would indicate if there might be blockage in the tubes. The fan clutch should cause the fan to roar when you first start and after a couple of minutes quiet down. I had the same problem with my 350 LE and I ended up re-core my radiator. While I was in there I replaced it all. Hoses, belts, thermostat, and other misc stuff.
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