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#1049194 - 03/24/17 02:14 AM Radiator Fan On Constantly....  
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longislandcamper Offline
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longislandcamper  Offline
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Port Jefferson Station, NY
Let me preface this by saying that most of what I know about working on cars I've been taught by forum searches, youtube and my buddy these past few weeks. When I got my Monte last month it marked the first time I've owned 2 cars at the same time which gives me the capability to work on one while driving the other. So far, so good.

My Monte radiator fan runs whenever the engine is on, no matter what temperature it's at. I've got the mechanical fan. My searches on this topic lead me to believe that there are 2 types of fan clutches, thermal and non thermal. A thermal fan clutch will engage once the radiator reaches a certain temperature. A non thermal fan clutch will run whenever the engine is on.

Do I have that right so far?

When the car is off I have tried turning the radiator fan and there is definitely some resistance as I turn it which I believe is a good thing. It's a metal fan. I out my hand on the front of the fan clutch and it was smooth. I didn't feel any coils and I'm not about to take the shroud off right now since it's late and cold. lol I'll probably get around to looking at it on Saturday when it's a bit warmer.

Anyway, if my suspicions are correct then I have a non thermal fan clutch and it's perfectly fine that it runs constantly. Does it sound like I'm on the right track?

#1049195 - 03/24/17 02:57 AM Re: Radiator Fan On Constantly.... [Re: longislandcamper]  
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ChasUno Offline
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Bradenton, FL
From my understanding, a thermal (viscous coupling) fan will still turn with the engine running, regardless of the operating temperature. What DOES change depending on the temperature, is how much resistance the viscous coupling gives.

A better way to check is to try and turn the fan by hand at cold engine temps, and then after the engine has got up to temp. (both with the engine OFF, obviously).

A viscous coupling fan, when cold, you should find it very easy to turn the fan by hand. This is because the viscous coupling is designed to give least resistance when cold, thereby not turning as much per engine revolution and thus not cooling an already cold engine. When hot, you should now find it much harder to turn the fan by hand. The viscous coupling will be doing its job by causing greater resistance, which in turn, causes the fan to spin more in relation to engine revolutions compared with when the engine is cold. This increases the cooling effect of the fan, which is needed when the engine reaches higher temperatures.

A fixed fan will be impossible to turn by hand, unless the drive belt is slipping. It's driven by the crankshaft pulley, so if you try and turn it, it would only turn if the engine turns with it. If your drive belt is in good condition and tensioned correctly, you will find this almost impossible to do. That's exactly the behavior you would expect from a fixed fan.

Also bear in mind that as most MCSS models came equipped with AC, the fan (I think) does need to run at all times (albeit not always at full power) to enable the condenser to do its job. Modern cars fitted with AC and electric cooling fans often have an additional electric fan just for the condenser. A viscous coupling will still enable the fan to turn enough at cool temps to facilitate air flow through the condenser. This is also why when some owners convert older cars to electric fans and delete the viscous coupling, they have issues with the AC not working as effectively due to lack of air flow through the condenser during certain conditions. Some fit another switch in the system to trigger the fans to run at lower speeds, even if the engine temp doesn't require it.

Regarding your comment, "A thermal fan clutch will engage once the radiator reaches a certain temperature. A non thermal fan clutch will run whenever the engine is on.", I think you are confusing a fixed fan with a viscous coupling (thermal) fan clutch - both are 'mechanical' fans. A fixed fan has no clutch and will indeed run at all times, its speed is directly related to engine revolutions, regardless of temperature. A viscous coupling fan will also run at all times, the difference being how much it turns in relation to engine temperature and engine speed. The ratio of fan turns to engine turns varies depending on temperature (increases when warm, decreases when cold).

That's my understanding of viscous coupling fans vs fixed fans.


1986 Monte Carlo SS

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#1049200 - 03/24/17 10:48 AM Re: Radiator Fan On Constantly.... [Re: longislandcamper]  
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LXXXIV SS Offline
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LXXXIV SS  Offline
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Lower Peninsula, Michigan
If when you start the car for the first time in the morning, you hear a loud howl which last about 30 seconds or so, then quiets down... everything is working normally. This means the fan is running at full speed while it gets ready to take over it's duties.

Whenever the car gets too hot, you'll hear the same howl until it cools down enough. The fan will always turn while the motor is running. It just turns at different speeds.

#1049203 - 03/24/17 02:38 PM Re: Radiator Fan On Constantly.... [Re: longislandcamper]  
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kevins88ss Offline
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Southern Maine
Thermal fan explanation

The air temperature coming through the radiator is sensed by the bi-metal thermal spring on the front of the thermal fan clutch. It expands and contracts with the change in air temperature operating a valve inside of the clutch. When cold, the silicone drive fluid is pumped from the working area to the reservoir. When hot, the valve opens allowing fluid from the reservoir to be transferred to the working area thereby increasing the fan speed. The clutch disengages as the air temperature decreases, closing the valve and allowing the silicone fluid to be pumped back into the reservoir.
A thermal fan clutch is engaged on a cold startup because the fluid drains into the working area when the engine is shut off. The fan clutch will slow down shortly after startup as a result of a pumping action produced by a difference in speed between the shaft and the body of the clutch.

Most models are designed to duplicate original equipment performance. Some Chevrolet/GMC truck models are specifically designed to engage at lower temperatures than the original equipment parts that they replace

#1049211 - 03/25/17 12:59 AM Re: Radiator Fan On Constantly.... [Re: longislandcamper]  
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longislandcamper Offline
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longislandcamper  Offline
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Port Jefferson Station, NY
When I got home from work today I went in the garage and tried to turn the fan. It spins but there is definitely some resistance to it. Teh car hadn't been started in a few days so the engine was cold.

I then started the car and you could feel a huge rush of air if you were by the front tires. I had a rolled up magazine and I began to insert it in the fan blades just to see how forceful the blades were and I got shreds of paper coming out. After about a minute or so the engine compartment got a little quieter and I didn't feel that same rush of air if I was standing by the front tires. I began to insert the rolled up catalog and again got shreds of paper coming off.

I was idling at about 1,600 RPM's the entire time. A few times I popped the gas pedal but the idle always returned to 1,600 RPM's, even as the water temp rose. Putting the car in drive dropped the RPM's to about 1,200.

#1049221 - 03/25/17 04:14 PM Re: Radiator Fan On Constantly.... [Re: longislandcamper]  
Joined: Sep 2011
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LXXXIV SS Offline
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LXXXIV SS  Offline
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Lower Peninsula, Michigan
Originally Posted by longislandcamper
When I got home from work today I went in the garage and tried to turn the fan. It spins but there is definitely some resistance to it. Teh car hadn't been started in a few days so the engine was cold.

I then started the car and you could feel a huge rush of air if you were by the front tires. I had a rolled up magazine and I began to insert it in the fan blades just to see how forceful the blades were and I got shreds of paper coming out. After about a minute or so the engine compartment got a little quieter and I didn't feel that same rush of air if I was standing by the front tires. I began to insert the rolled up catalog and again got shreds of paper coming off.

I was idling at about 1,600 RPM's the entire time. A few times I popped the gas pedal but the idle always returned to 1,600 RPM's, even as the water temp rose. Putting the car in drive dropped the RPM's to about 1,200.



What you found was that the fan-clutch is working normally. You'll know it's time to replace the clutch when it doesn't produce that high speed flow of air and howling noise at startup.

As for the high idling, that's a separate issue, unrelated to the fan.

#1049226 - 03/25/17 11:45 PM Re: Radiator Fan On Constantly.... [Re: longislandcamper]  
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longislandcamper Offline
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longislandcamper  Offline
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Port Jefferson Station, NY
Sounds good, thanks.

Last edited by longislandcamper; 03/26/17 12:20 AM.
#1049491 - 04/02/17 12:42 AM Re: Radiator Fan On Constantly.... [Re: longislandcamper]  
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longislandcamper Offline
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longislandcamper  Offline
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Port Jefferson Station, NY
But how fast should the fan be going? Yes, I get the big wish of air upon startup that dies down after 20 seconds or so but the radiator fan still seems to be going pretty fast.

It definitely slows down because you can feel it. When the car is in my garage and the hood is up then the front of the car is like a wind tunnel and the papers on my walls blow around until about 20 seconds after starting. If you stand at the grill then you can feel your pants getting sucked into the grill.

Eventually you don't have the whoosh of air blowing the papers around and your pants don't feel like they're getting sucked as hard into the grill.

#1049496 - 04/02/17 02:38 AM Re: Radiator Fan On Constantly.... [Re: longislandcamper]  
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Jameson Offline
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Jameson  Offline
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Elizabeth City, NC
The fan isn't going to stop spinning with the engine running, I feel you're over thinking it because the operation sounds normal.


1988 Monte Carlo SS Eaton 112 5.3/T56 swap, Way to many mods to list.
2015 GMC Sierra Denali



#1049545 - 04/03/17 01:34 PM Re: Radiator Fan On Constantly.... [Re: Jameson]  
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longislandcamper Offline
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longislandcamper  Offline
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Port Jefferson Station, NY
Originally Posted by Jameson
The fan isn't going to stop spinning with the engine running, I feel you're over thinking it because the operation sounds normal.


I'm just a little paranoid because the needle was pegged all the way to the right when I bought it and it was also leaking coolant due to a loose hose clamp. I swapped out the gauges recently and sometimes the temp gauge works and sometimes it doesn't.

#1049546 - 04/03/17 02:25 PM Re: Radiator Fan On Constantly.... [Re: longislandcamper]  
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Witness86SS Offline
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Hatfield, PA
Originally Posted by longislandcamper

I'm just a little paranoid because the needle was pegged all the way to the right when I bought it and it was also leaking coolant due to a loose hose clamp. I swapped out the gauges recently and sometimes the temp gauge works and sometimes it doesn't.


If your radiator is full, the top hose is hot, the fan is spinning and your overflow tank isn't overflowing then you are fine.


Justin
1986 Black SS
Upgrades: 350 L05 - Hooker Longtubes - FlowMaster True Dual 2.5" - Electric Cutouts - Electric Fans - Transcooler - Proforged Steering Kit - Astro Shaft - AR62 OUTLAW II Wheels - Energy Suspension Bushings - Bitflipper Chip - 87 ECM - Moog Springs and Ball Joints - Bilstein Shocks - Bucket Seats
#1049547 - 04/03/17 02:28 PM Re: Radiator Fan On Constantly.... [Re: longislandcamper]  
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LXXXIV SS Offline
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LXXXIV SS  Offline
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Lower Peninsula, Michigan
Originally Posted by longislandcamper
Originally Posted by Jameson
The fan isn't going to stop spinning with the engine running, I feel you're over thinking it because the operation sounds normal.


I'm just a little paranoid because the needle was pegged all the way to the right when I bought it and it was also leaking coolant due to a loose hose clamp. I swapped out the gauges recently and sometimes the temp gauge works and sometimes it doesn't.


We've already established that your fan is working properly. The fan will always be turning. If it ever stops turning when the motor is running, then you've got a problem.

If the temp gauge is working intermittently, like yours, then you have an electrical, or sensor problem.

The first thing you need to do is get on Ebay and buy the factory service manual for your year monte. You also need the electrical troubleshooting manual that accompanies it.

Find a used original copy, and NOT one on CD, or from GM Restoration Parts. The GM restoration parts manual is garbage.


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