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11/22/12 4:28pm - Original Message: 'Flex Fan or no Flex Fan'
tinbender
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edgwood, MD - USA

Vette(s):
1975 convertible,with the hard top and power streering.it a 350 L48 with auto trans. the color is light blue.

Joined: 11/1/2007
Posts: 736
Still working on my overheating problem,I am going to change both the upper and lower hoses and the water pump. My reasoning is I don't know how old these parts are. I have a flex fan that is still in the box and was wondering if it would matter if I took off the clutch fan ...car dose not  have A/C. So would it matter if I changed the fan?
                      Thanks Rick
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11/22/12 5:06pm - Reply: 'Re: Flex Fan or no Flex Fan'
Gunslinger
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Frederick, MD - USA

Vette(s):
1969 convertible L71 427/435 4-speed black interior

Joined: 9/8/2003
Posts: 3398
Your overheating problem could possibly be caused by a bad fan clutch...it does happen.  One way to check it is to let the engine run up to normal temperature than stop the engine.  If the fan keeps on spinning the fan clutch is bad.  A good fan clutch should stop nearly as quick as the engine.  

Outside of that, I would keep the fan clutch...it's there for a reason.  With a flex fan you might gain a lot of fan noise.  If the flex fan is made of fiberglass, it can develop stress cracks with time and a blade can break off while spinning and fly into something under the hood.  That doesn't happen often but it's been known to happen.

What are the conditions your engine overheats?  Does it do so only at highway speeds, low speed or both?  Is it actually overheating?  You could have a bad sending unit, gauge or thermostat.  Has the cooling system been pressure tested (along with the radiator cap)?  Are the seals around the radiator in place?  Is the air deflector under the front end there?

Just replacing parts may not find the problem.


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11/22/12 5:35pm - Reply: 'Re: Flex Fan or no Flex Fan'
rod7515 Lifetime Member
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Red Lion, PA - USA

Vette(s):
1974 White 350 Corvette, TH400 Automatic 1972 Tangerine /Go Mango Convertible 383 Stroker, 2004r Automatic

Joined: 10/27/2006
Posts: 1172
Im in Agreement with not using a flex fan. Ive seen the damage they can do when they let go. I would hate to see someone near it at that time. The one I know of that came apart was an aluminum blade that went thru the shroud and dented the hood. Probably come thru one of our fiberglass hoods.
Remember that the car used to cool so you know if all your components are working its a proven system. You havent done any engine work that would have changed anything? When does the engine overheat. If you want to try another fan clutch I have the one off the 72 I am not using. You can give it a shot. Also does your shroud have any breaks in it? Have you checked the actual temp? Does it push coolant out the over flow while running or when shut off? Did you try changing the thermostat? Does the lower hose collaspe while driving. Im not that far from you if you need a hand sometime.
Rodney


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11/22/12 7:23pm - Reply: 'Re: Flex Fan or no Flex Fan'
F4Gary Gold Member
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Grapevine, TX - USA

Vette(s):
1972 LT-1 convertible with factory air.

Joined: 8/26/2006
Posts: 870
What kind of shape is the radiator in?

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11/22/12 9:10pm - Reply: 'Re: Flex Fan or no Flex Fan'
KDADDY79
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Dutchess County, NY - USA

Vette(s):
White '79 Corvette. It's a driver.

Joined: 8/27/2007
Posts: 2484
I replaced the fan clutch on my '79 a few years ago. Solved the problem and it was an easy job.
I'd shy away from the flex fans, too.
Kevin


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11/22/12 9:27pm - Reply: 'Re: Flex Fan or no Flex Fan'
tinbender
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edgwood, MD - USA

Vette(s):
1975 convertible,with the hard top and power streering.it a 350 L48 with auto trans. the color is light blue.

Joined: 11/1/2007
Posts: 736
 I changed the clutch on the fan two years ago,when I take the car out it overheats as soon as it starts to get warm.(don't take long).The hose going into the the thermostat housing gets really hot and if you grab it you can feel the pressure on it,the strange thing is the radiator cap is cold and has no pressure on it.I've been told by a couple of people the the bottom hose has clasped or that the impeller on the water pump is bypassing. So not knowing when these three things were last worked on I decided to change them.As for the radiator I will look it over while I have everything apart.Oh I did change the thermostat and it didn't help.  As for the flex fan from your experiences I think I will stay with the factory fan setup.As soon as I find a way to move the car to a place to work on it I will change the parts and post the results.....Unhappyright now I'm a little gun shy on working on anything in front of my house.
                Thanks Rick
 
    P.S Thanks for the offer Rod I'll keep you in mine.


|UPDATED|11/22/2012 7:27:32 PM (AZT)|/UPDATED|


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11/23/12 10:37am - Reply: 'Re: Flex Fan or no Flex Fan'
danascar
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Germansville, PA - USA

Vette(s):
1974 Coupe 358ci 4 speed Black w/Medium Saddle interior w/79 custom leather seats. 1999 Covertible, 6 speed, Atomic orange, Oak interior

Joined: 1/28/2010
Posts: 763
Try removing the T-stat and run it....you could have gotten a bad new one. Hose going into T-stat hot and under pressure sounds like T-stat not opening

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11/23/12 8:12pm - Reply: 'Re: Flex Fan or no Flex Fan'
Andy61
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, - Australia

Vette(s):
1969 convertible blown 350 4 speed manual

Joined: 11/20/2012
Posts: 15

There may be another issue namely with your engine, check the water and make sure there is no oil in it and also check the oil on the dipstick, if the oil on the dipstick is creamy coloured, you may have done a head gasket. Advanced timing will also make the engine run at a higher temp, I had the same problem with overheating and found the distributor lock bolt had loosened and the timing advanced on it own enough to cause overheating.

 
Just a thought.


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11/23/12 8:23pm - Reply: 'Re: Flex Fan or no Flex Fan'
tinbender
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edgwood, MD - USA

Vette(s):
1975 convertible,with the hard top and power streering.it a 350 L48 with auto trans. the color is light blue.

Joined: 11/1/2007
Posts: 736
 Well I got the top hose replaced,water pump replaced then the problem Shocked ....I couldn't find the right bottom hose. I found plenty of hoses ,but none had the spring so I called corvette america and order one. Should be here Tuesday. I want to give Rich (Yostusota) a thank you for the phone help today. Well when I'm done everything except the radiator has been changed in the cooling system so I will see if problem solved.
                                    Rick
 
           Only bad thing is I have to leave the car on the street till fixed


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11/23/12 8:31pm - Reply: 'Re: Flex Fan or no Flex Fan'
tinbender
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edgwood, MD - USA

Vette(s):
1975 convertible,with the hard top and power streering.it a 350 L48 with auto trans. the color is light blue.

Joined: 11/1/2007
Posts: 736
 I think gunslinger hit the nail on the head the spring on the bottom hose was shot,But instead of just doing it I decided to replace everything (no telling how old the hoses were and water pump was original.No water in the oil (thank goodness)
                                     Rick


|UPDATED|11/23/2012 6:31:41 PM (AZT)|/UPDATED|


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11/24/12 1:31pm - Reply: 'Re: Flex Fan or no Flex Fan'
JohnRR
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Joined: 2/22/2011
Posts: 110
You guys talk about Flex Fans letting go.  The previous owner of my '73 BB had the stock clutch fan fly apart.  It took out part of the shroud and blew a large hole in the hood!  It took him 3 days on the road to get parts and get it fixed.  I never liked the sound of the fan on this engine. At higher RPM's all I can hear is the fan.  It makes me want to shift to get rid of the crappy noise.  I'm going with DeWitts dual electric fans and hopefully, they'll only come on in traffic.

John


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2009 Z06 Mostly Stock
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11/24/12 1:37pm - Reply: 'Re: Flex Fan or no Flex Fan'
Gunslinger
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Frederick, MD - USA

Vette(s):
1969 convertible L71 427/435 4-speed black interior

Joined: 9/8/2003
Posts: 3398
If your fan is as loud as you say then someone may have replaced the original fan clutch with an incorrect one.  That's not uncommon when they're replaced.  

I will say that if you're not concerned about originality electric fans are the way to go.  


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Poet...Mystic...Soldier of Fortune. As always...self-absorbed, adversarial, c o c k y and in general a malcontent.

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11/24/12 10:58pm - Reply: 'Re: Flex Fan or no Flex Fan'
yostusota
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York, PA - USA

Vette(s):
1969 daytona conv. all original 350 350 380 4 sp w/air..and hard top

Joined: 5/18/2010
Posts: 1518
Flush out that radiator while you got it apart....I mean alot!!! I flush mine 2 times every year....it looks like stalactites in there!! Or I hate to say remove it and have it cleaned.....but...flush kits are cheap and clean out the goop really good...LMK!!!!

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11/24/12 11:32pm - Reply: 'Re: Flex Fan or no Flex Fan'
JohnRR
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Joined: 2/22/2011
Posts: 110
If you're flushing it twice a year and getting out lots of junk, then it sounds like there is something else wrong with the cooling system.  

John


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2009 Z06 Mostly Stock
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11/25/12 3:13am - Reply: 'Re: Flex Fan or no Flex Fan'
lukesvette Lifetime Member
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HOWELL, NJ - USA

Vette(s):
1979, Targa Blue (72 Color), Pace Car rear spoiler, L88 hood, Dark blue factory interior, 525HP 406, HD 700R4, 370 gears,Steeroids, composite rear spring, TT IIs wrapped in T/A Radials.

Joined: 5/18/2004
Posts: 6806
Rick, I had the same symptoms and was finally cured by a bottom hose with the spring. What was happening was the bottom hose without the spring would collapse while driving. The spring cured it - everything else on the car was new so no other gremlins.

Hope the bottom hose solves the mystery for you.Smile

Paul


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11/25/12 7:49am - Reply: 'Re: Flex Fan or no Flex Fan'
yostusota
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York, PA - USA

Vette(s):
1969 daytona conv. all original 350 350 380 4 sp w/air..and hard top

Joined: 5/18/2010
Posts: 1518
John...the problem with my car is that the radiator is original and had little to no maintenance in its life..I may remove it this winter and get it cleaned out...hope Rick doesn't have to do that and the new hose with the spring works out.

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11/27/12 7:56pm - Reply: 'Re: Flex Fan or no Flex Fan'
tinbender
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edgwood, MD - USA

Vette(s):
1975 convertible,with the hard top and power streering.it a 350 L48 with auto trans. the color is light blue.

Joined: 11/1/2007
Posts: 736
Got my new hose today from corvette America. If all go right I'll be putting it on Thursday afternoon( got a interview in the morning) ....so I will post after I try it out will let you all know if successful. Rick

|UPDATED|11/27/2012 5:56:50 PM (AZT)|/UPDATED|


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11/27/12 10:09pm - Reply: 'Re: Flex Fan or no Flex Fan'
Norsky Lifetime Member
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Twin Lakes, CO - USA

Vette(s):
SOLD - "The Toy" - 1970 Convertible
SOLD - "The Beast" - 1990 ZR-1 (#682)
"BLKBRRD" - 1978 Trans Am, 400ci/285hp, 4 spd, Black w/black interior, Hurst t-tops

Joined: 1/23/2002
Posts: 6714
Hope the new lower does the trick.  Running abit without the t-stat in place would also let you see it the radiator is indeed cooling enough.  If there is a build up of rust and/or scale in the radiator that could impede the cooling.  A fellow on the Model A club I've joined has recommended running pure vinegar in the cooling system to dissolve the crub.  He claims it cleaned everything out clean as a whistle.  I know the cooling systems between a Model A and a C3 Corvette are quite abit different but they're very similar in function.
 
Also make sure the radiator support seals are in place.  Any air slipping through the gaps between the radiator support and the radiator is air that isn't helping to cool.


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Jim Olson 

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11/27/12 11:12pm - Reply: 'Re: Flex Fan or no Flex Fan'
kstyer Lifetime Member
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CUYAHOGA FALLS, OH - USA

Vette(s):
1975 C3 Red, T-Tops, Black Interior. All I need is time and money! Getting there!

Joined: 12/2/2003
Posts: 6410
Just two comments.
 
Don't forget to check the actual flow.  I have seen water pumps that seem okay but have impleller blades rotted or rusted to the point they either are not there or have come loose from the shaft.    It just won't pump the coolant.   Uncommon, but not rare.
 
Removing the thermostat completely will allow a quick check, but when driven can acutally CAUSE and overheat problem.   The stat acts like a restrictor to flow, slowing it down at high engine speed.   IF the coolant flows too fast it can travel through the radiator quicker than it can be cooled, resulting in still too hot coolant going back into the engine, and not cooling, but overheating instead.
 
While this usually does not happen at low to medium engine RPM,  many driving conditions can cause this to happen.   Often racers will remove the t-stat but install a restrictor in it's place.  This is nothing but a large washer with a hole in it to control the coolant flow.
 
Of course removing the t-stat and starting the car will allow you to see the volicity of the coolant flow through the radiator, if you can see in the tank.  Some of our designs may prevent getting a clear view, but most will allow it.


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11/30/12 8:00am - Reply: 'Re: Flex Fan or no Flex Fan'
knotacare
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Newark, DE - USA

Vette(s):
1968 Conv, 454HO,500HP-600TQ, TKO-600,3:70 HD rear,hotrod air, custom paint & suspension,1973 Ruby Red,T-top, 383 Stroker, TK)-500,frame off restro, 1977 Yellow (1 of 51 ) L-48 4 spd, 99% original.

Joined: 7/26/2004
Posts: 453
Good flex fans work fine & will tolerate 10K RPM. I've used them on various cars for many yrs with no problems. If your car is overheating & you have a correctly placed fan, clutch,flex or electric you have other issues. Making sure all air goes through the radiator is a real problem & will cause overheating at highway speeds on C-3's. If your bottom hose is being sucked in your radiator is probably clogged. Water wetter will really help bring the temp down 10-20 degrees & running a 25% antifreeze mixture will help too. water dissipates heat much better than antifreeze, but you need some antifreeze to control corrosion. I personally use flex fans on 2 high performance engines & they keep the engine right at 175-180 degrees in all weather. I also have one with electric  fans that also work  fine. Flex fan can be noisy , but if you exhaust is noisy you'll never notice it.  So I think it really comes down to a personal choice. Flex fans can be adjusted in & out to really get the proper air flow which is critical to coolling efficiency.
Alan


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