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Old 07-15-2013, 10:42 AM
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s10 v8 idle overheating problem

Hello guys I have an issue here with overheating at idle and only at idle on both of my chevy s10's one is a 86 other is a 96. This is mostly info about my 96 but both trucks are pretty much the same outside of engine combo's and power. I can drive at 25 mph or up and have no problems with truck running hot what so ever even in 90 degree weather and high humidity.

Truck runs about 180 to 190 until I get stuck in traffic and have to sit for several minutes. So yesterday I wanted to see just how much of a problem I have so it was running a steady 190 then I sat outside my house and sat there watching it idle and the temp gauge and within about 5 minutes it got up to 210 then after a few more minutes it got up to 220. Temp gauge shows 210 then a mark then 250.

I purchased a laser thermometer gun and it did register almost the same as what the gauge did on the thermostat housing and read over 215 on the radiator and over 200 plus on the corner of the aluminum head.

Everything on cooling system is fairly new and very clean as I don't drive that much and all new 50/50 mix antifreeze. I am running a regular 160 thermostat with two holes drilled for bypass and I have also ran a 180 stat and there is no difference in how the temperatures go. I have tired the high flow thermostat before but they make the engine run too cold down the highway and during winter months its horrible so can't use them. I am currently using a high flow water pump oem style and I also tried using a stock oem water pump and neither one makes a difference in temperature for idle.

I have more then enough radiator as I am running an aftermarket all aluminum 29/17 two core radiator and each row is one inch each so that is not the problem there. Running a flex fan that pulls very good as feel anyways as you sit at idle if you put your hand toward the radiator you can feel it pull air so I am thinking its a shroud type issue as you can see in my pictures its a home made deal and nothing fancy. Does anyone have any suggestions as to what I should or can do.

I don't think a clutch fan will make any difference but I don't know as I have never used one just read some people don't like them and some are ok with them. From what I read flex fans work better for low speed air flow. I honestly want to keep my flex fan as I like it running all the time and not have to depend on a clutch style to engage as I like the peace of mind its running. I will do what I have to do to get this fixed.
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Last edited by eric32; 07-15-2013 at 10:52 AM.
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Old 07-15-2013, 01:03 PM
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Probably not what you want to hear ,First loose the flex fan they look good but I have had problems with every one I have had,

Second and Most Important is you need a shroud the cut out needs to go as close to size of your fan as possible without touckind ,don't forget engine torques to the right , and the fan blades need to set inside the shroud about 75% only 25% out as this will force All of the air through complete radiator not just the diameter of the fan ,,or use an electric fan and a shroud (,my 1st choice,). if you use a clutch fan try to find the one with a spring and oil viscous coupler I will cool at idle and disengage at highway speeds .
this puller setup works for me.
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Old 07-15-2013, 01:41 PM
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Quote:
Originally Posted by eric32 View Post
Hello guys I have an issue here with overheating at idle and only at idle on both of my chevy s10's one is a 86 other is a 96. This is mostly info about my 96 but both trucks are pretty much the same outside of engine combo's and power. I can drive at 25 mph or up and have no problems with truck running hot what so ever even in 90 degree weather and high humidity.

Truck runs about 180 to 190 until I get stuck in traffic and have to sit for several minutes. So yesterday I wanted to see just how much of a problem I have so it was running a steady 190 then I sat outside my house and sat there watching it idle and the temp gauge and within about 5 minutes it got up to 210 then after a few more minutes it got up to 220. Temp gauge shows 210 then a mark then 250.

I purchased a laser thermometer gun and it did register almost the same as what the gauge did on the thermostat housing and read over 215 on the radiator and over 200 plus on the corner of the aluminum head.

Everything on cooling system is fairly new and very clean as I don't drive that much and all new 50/50 mix antifreeze. I am running a regular 160 thermostat with two holes drilled for bypass and I have also ran a 180 stat and there is no difference in how the temperatures go. I have tired the high flow thermostat before but they make the engine run too cold down the highway and during winter months its horrible so can't use them. I am currently using a high flow water pump oem style and I also tried using a stock oem water pump and neither one makes a difference in temperature for idle.

I have more then enough radiator as I am running an aftermarket all aluminum 29/17 two core radiator and each row is one inch each so that is not the problem there. Running a flex fan that pulls very good as feel anyways as you sit at idle if you put your hand toward the radiator you can feel it pull air so I am thinking its a shroud type issue as you can see in my pictures its a home made deal and nothing fancy. Does anyone have any suggestions as to what I should or can do.

I don't think a clutch fan will make any difference but I don't know as I have never used one just read some people don't like them and some are ok with them. From what I read flex fans work better for low speed air flow. I honestly want to keep my flex fan as I like it running all the time and not have to depend on a clutch style to engage as I like the peace of mind its running. I will do what I have to do to get this fixed.
The motor runs normal temps on the highway. That tells me that you have enough radiator and that the air has a way in and a way out. The problem is with the amount of air that the fan is pulling through the radiator and that ain't much. Air, water and electricity will always take the route of least resistance. The route of least resistance in your case is the fan pulling air from everywhere except through the radiator. It's obvious from your photos. It's pulling air from underneath, from the top and from the sides behind the radiator, but not THROUGH the radiator.

Either buy a commercially-available shroud or construct one yourself, closing the fan off so that it cannot see anything but the radiator. Keep the flex fan if you want to and see how it operates with a shroud. I don't like flex fans because they generally don't have enough pitch to move enough air. If you lay the fan blade down on the work bench and measure from the edge of one of the vanes to the work bench surface, you will find the pitch. I normally like about 2" to 2 1/2" of pitch on a steel OEM-type fan blade.

You might think you are doing yourself a service with a flex fan, but think about it. It takes fan speed to lay the blades back and that speed comes from the motor turning the fan. Now, if it takes hp to lay the blades back, how in the name of all that is holy are you saving any power?

Also, I think you are misunderstanding how a fan clutch works. It's like a small torque converter. There is no on or off, just a certain amount of slip based on resistance of the fan blades to the air, so that it drives the fan blade at full speed at idle and gradually begins to slip as the rpm's increase because you don't need any fan at all at highway speeds over about 35.

Another misconception you and others have is about operating temps. An internal combustion motor needs to run at 195 degrees or more to burn off acids and other non-combustibles.

So, there you have it.
1. Shroud with fan blades halfway in and halfway out or 2/3 in and 1/3 out, you get the idea I'm sure. Leave 1" of clearance all the way around between the tips of the blades and the inside of the shroud. The motor is on flexible mounts and torques over under power.
2. A real fan blade assembly with 2" - 2 1/2" pitch. 7-blade, 18" OEM steel is best. If you really want to move some air, use a fan blade assembly from an 80's Olds diesel. I think the pitch is right at 3". Be careful and don't choose a fan assembly from a serpentine arrangement. The blades are oriented differently. Stand in front of the radiator and look down at the top of the closest blade. If the orientation is Northwest to Southeast, it's a conventional fan blade. If the orientation is Northeast to Southwest, it's a serpentine fan blade assembly.
3. 195 or higher high-flow thermostat
4. Fan clutch

Last edited by techinspector1; 07-15-2013 at 01:52 PM.
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Old 07-15-2013, 02:31 PM
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I'll echo the others on getting rid of the flex fan and using a good quality clutch fan with six or seven blades.

The other thing to consider is, are you using ported or manifold vacuum for the distributor? With ported vacuum, you get no advance at idle. Factory cars that use ported vacuum also use an thermal vacuum switch that switches the distributor to full manifold vacuum if the car starts to overheat.
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Old 07-15-2013, 04:04 PM
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Wow what a lot of info thanks guys. I will have to see about the shroud and I do have some knowledge on the cutch fans and how they work its just I never owned anything that I drive that has one except the wife's envoy but its not a performance vehicle with a customized v8 installed.

Now from what I read on other forums doing a google search one side says a flex fan worked better then a clutch fan and dropped there temperature 20 degrees at idle and worked way better just changing out the fan. And others said using a clutch fan was way better then using a flex fan. I have no experience when it comes to this stuff.

My first idea is making a bottom piece to go around the bottom of my home made shroud so the air flow wont be blowing towards the bottom of the ground on the bottom half and help for the air being pulled through the radiator to be better concentrated through the fan radius.

What are you opinions on this? If I were to switch over to a clutch fan I feel like it might not work still cause it will basically be blowing the air the same way regardless of what fan I use. I know that a proper shroud is very important and I bet if I get it straightened out it will work fine. If that is the case and what I got does not work I don't know anything about getting a replacement shroud as my trucks are both cut and customized to fit a bigger radiator in the front in order to cool a v8 and a factory shroud for a s10 will never fit.

I understand the temp has to be around 190 in order to burn and run good and mine is about 190 during the summer months and 180 during winter but during summer like I posted it will get too hot and run as high as 230 and still want to climb as I turned it off yesterday when it got to that point as it never stopped.

As far as timing goes I ran manifold vacuum advance before cam swap but changed out heads and put a more performance cam and developed carb off idle backfire problem and doing different timing settings made no difference till I had to run ported as it running off of manifold with my initial they did not get along with the carburetor and no amount of changes would get rid of it till I changed from full manifold to ported and a little more initial and regardless it did not make any difference on idle temperature. I would be happy to do a clutch fan in order to not have to install a electric setup. Thanks guys for your help as it is worth its weight in gold as I need to get this fixed.
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Old 07-15-2013, 04:13 PM
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My current 6 blade flex fan is 17 inches and I looked at summit and I would not know where to start if I need to go to a clutch fan setup.
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Old 07-15-2013, 04:26 PM
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I forgot to mention .if your radiator is standard heigh and wigth a 4.3 v6 s10 fan shroud should almost be a bolt on since is is same demensions as a 350 (not the lengh),,I saw you stated it had 1 in tubes that is good.Hope these post help you.
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Old 07-15-2013, 05:45 PM
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Use a 5-blade fan and a OE thermo-controlled clutch fan, not a El Cheapo viscous controlled fan. A thermo-controlled clutch fan has a bi-metal spring in the front to sense air temperature coming through the radiator. When the air temperature ithrough the radiator reaches a per-determined temperature, the bi-metal spring locks the fan clutch and the fan becomes a solid fan. That is designed to occur at idle speeds on hot days (i.e: traffic lights). The fan free-wheels and does not rob horsepower at higher RPM when lack of air flow is not a problem. .

Use a 5-blade fan. A 7-blade fan acts as an air-dam and restricts air flow at highway speed. Five-blade varible-pitch fans work with a proper designed fan shroud. Some high-performance GM engines came equipped from the factory with varible pitch fans to prevent horsepower loss at high RPM.
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Old 07-15-2013, 06:39 PM
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The factory clutch fan and shroud still work the best in my opinion. I am not a fan of the flex fans at all. You can try it with a shroud it may or may not work.
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Old 07-16-2013, 06:14 AM
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Just by coincindence, a discussion about the used of a 5-blade fan in comparison with a 7-blade fan as used on a GM thremo-controlled clutch occurred the last Saturday in June at the monthly "Cars and Coffee" outdoor car show. The several Corvette owners at the gathering agreed that the 5-blade fans coolled better than the 7-blade fan on their Corvettes and they said they have tried them both. According to the Vette owners, GM put 5-blade thermo-controlled clutch fans on Corvettes, with or without A.C.

That prompted me to experiment and change a 1992-1995 7-blade steel fan and thermo-controlled clutch back to the original 1991 5-blade steel fan and thermo-controlled clutch on my 1991 S10 Blazer 4x4. I immediately saw a slight improvement in cooling but only at highway speed with no difference in traffic. GM used a 5-blade steel fan on S10 Blazers with RPO C60 A.C. through 1991. Starting in 1992 through 1995, GM used a 7-blade steel fan and starting in 1996, GM used a 11-blade plastic fan arrangement.

Either a 5-blade or a 7-blade fan was standard equipment with RPO C60 A.C. The RPO C42, without A.C., were equipped with 3-blade fans. My 1963 Pontiac Cantalina with a RPO Police and Ambulance option without A.C. was equipped with a 5-blade solid fan, and no fan shroud. The 1963 Pontiac with Police and Ambulance option, witout A.C., had a low fin count, 3-tube radiator for improved air flow at high speed. Only the 1963 pontiacs equipped with A.C. had a fan shroud and thermo-controlled fan clutch.

There is no definitive proof which number of blades and what type of fan is best under all driving conditions.

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Old 07-16-2013, 08:47 AM
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I did some research and according to what I found there is a standard duty then heavy duty and then super duty clutches for a clutch fans. Now checking out summitracing they only have standard duty clutch fans and the best you can get is either a heavy duty or super duty clutch setup but since they don't have any heavy duty style clutch fans I don' know what to do about that. But I did find that summit also has aluminum shrouds that you can customize from a 15 inch to 19 inch fan and I might go that route first before changing out the fan at this point but I am going to make some big changed to what I got first and maybe cut some of it back and get a factory shroud set up to maybe fix it to clamp on my existing one and close up the bottom. I am getting ready to do a paint job next week so all that will be addressed. But thanks to you guys I do have some ideas. If I have to go to a clutch fan the thermo style is the way to go but they all have different temp ratings and I don't know what to get on that as I would like it to be fully engaged at idle if around 190 to 200. Like I said I never had one on truck before. I also would like it to be either a 5 or 6 blade heavy duty steel fan not a cheapo plastic one.
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Old 07-16-2013, 09:49 AM
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I purchaced a severe duty fan clutch from auto zone around 90.00 as compared to gm I think around 250.00 with spring and viscous coupling I is for temp other is for rpm I use mine to pull a 33 camper and a car trailor so average around 6000-6500 lbs ,I cured my overheating problem ,only drawback I have if it is a problem for you it Does make more noise when it enguages a positive lock up and freewheels when not needed ,also it will spin when Cold until oil warms up then it works as designed ,,Works Great for me ,hope this helps

also you will need about an extra 1 in space between radiator and fan as it is thicker.
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Old 07-16-2013, 10:45 AM
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Quote:
Originally Posted by eric32 View Post
My current 6 blade flex fan is 17 inches and I looked at summit and I would not know where to start if I need to go to a clutch fan setup.
On mine I had fans from an intrepid I believe, shroud and all, one was switched, and i would leave it running always, the other was on a stat that turned it on a 200, in that configuration the hottest it ran was 210 in stop and go traffic at 40* weather. If I didn't have the switched fan on it ran 210 constantly and would creep higher in traffic. The previous owner had removed the seal at the back of the hood to the cowl and said that made a big difference as well.
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Old 07-16-2013, 11:50 AM
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The number of fan blades alone does not determine how much air a given fan will move. Automakers will vary the number of blades, blade spacing, blade shape, and fan diameter based on available space and even things like noise reduction. A seven blade fan is probably quieter, not necessarily more efficient than a five blade. Fans are also optimized for a specific RPM range. This is like designing a propeller.
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Old 07-16-2013, 12:57 PM
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When I changed from a 7-blade CCW rotation fan back to the OE 5-blade CCW rotation fan, I also replaced the thremo-fan clutch just because the OE clutch had 160,000 miles on it. Even with that many miles, the OE thermo fan clutch seemed to still be in good condition.

I installed a new AC Delco 15-4630 (GM-15709933), CCW rotation, thermo-controlled fan clutch. I purchased it from a seller on e-bay, NIB, for $60. It is still available from GM for $182 msrp.

LOL I did not know they still made those green fiberglass flex fans. A 1969 - 1970 Pontiac GTO with the Ram Air IV engine was equipped with a steel solid flex fan.
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