Cooling Issues

[westofb]

Originally Posted by Devil Pup

Thanks for all the feed back guys. . just to go over some things, the fan shroud is the correct one for the truck/radiator and the fan that is on it stuffs this shroud. its about half way in the shroud and half way out. "perfect according to the mechanic" i recently blew up the motor due to heat when the stock gauge went out and was reading normal. so i replaced the motor, flushed the radiator and made sure that the water pump was working and put the new gauge in. so im thinkin go back to the 180 degree T-stat at least? and i will check the coolant to make sure i have the right fluids in it. anything else i should be on the look out for or that i missed? thanks again everyone, Mark

when you replaced the motor did you upgrade any parts? lots of guys go to serpentine belt systems which can be had cheap. the water pump from the serp belt system looks the same as an old long water pump, but it is made to spin the opposite dirrection. If you have the wrong water pump (turning the wrong dirrection) no matter what you do, it will over heat! just throwing this out there, may not be the case at all, but no one else mentioned it.

Did you replace motor with a new one or junk yard find? Could have a head gasket problem? Just some points to ponder.

[ERASER5]

OK, you have a 3 row and it is good. Now, do you have a short or long water pump? A short wp usually ha the alternator on the drivers side, and the long wp usually has the alternator on the passenger side. There may be different length fan clutches too. A factory fan with no clutch would not have any let off. This could stall the water pump at certain rpms. I have plastic flex fan and no clutch. My fan really pulls the air, but screams if I wind the motor up.

Oh yea, a 4X4 shroud is different than a 2X. Deeper I think.

[Devil Pup]

the motor was mine just rebuilt. so all new seals and heads. the only thing i changed was the pulleys. i went to aluminum with dual belt because i put ac on. and it has a short pump on it with the alternator on the driver side. I don't quite understand what you mean about the clutch rpm spinning. i have no clue when it comes to the clutches to be honest.

[70k52wd]

I missed where you said radiator is new.
New pulleys? Are they the same size as old pulleys?

I'll try to explain a clutch as it was explained to me.
Clutch is oil filled. This is simplified, but as the rpm is low(idle) the oil gathers near the hub creating the fan to be fully engaged, as rpm increases, the oil spreads out to outer vein perimeter thus disengaging the clutch. Make sense?

[ERASER5]

As 75k52wd said, the clutch lets the fan stop increasing rpm at some point(unloading). A flex fan flattens out at a certain rpm(unloading). A factory fan with no clutch has no way to unload and may stall the water pump if the fan is catching enough air.

Fan clutches are expensive. At least the good ones are. If you want to go with a direct fan, you need some sort of flex fan. I recommend the plastic one from Flex-a-Lite. The aluminum flex fans will hurt your truck or kill you when, not if, it breaks. The steel flex fans will last a bit longer, but are still dangerous. The plastic flex fan works great with way less danger of breaking.

Or dump the fan altogether and run an electric fan. You will have to upgrade your alt to at least 100 amps too. Do a search for electric fans. There are a lot of threads about this.

The simple thing would be to find the correct clutch length and install that clutch. But simple is not as fun.

[mclairmo]

Originally Posted by Devil Pup

the motor was mine just rebuilt. so all new seals and heads. the only thing i changed was the pulleys. i went to aluminum with dual belt because i put ac on. and it has a short pump on it with the alternator on the driver side. I don't quite understand what you mean about the clutch rpm spinning. i have no clue when it comes to the clutches to be honest.

I guess nobody is reading my posts, but I will try one more time since I can sympathize with heating issues. You say you went to aluminum pulleys. These are almost always underdrive pulleys, which means the crank and water pump pulleys are the same diameter. Oem pulleys usually have the water pump pulley smaller than the crank pulley to obtain the proper ratio to keep the water pump spinning fast enough to move the water through the system. I know you changed these pulleys with the new motor and the old motor overheated with the old pulleys but I still don't know what kind of pulleys you had prior to the rebuilt motor. I would suggest that you use a smaller water pump pulley, about 6 inches or less in diameter, and a larger crank pulley, as close to 8 inches as you can find. At least you will then have optimized the water pump rotation speed.

[69GMCLonghorn]

On something that is known to have overheating problems, I would say possibly look into a toy fan.

But fact of the matter is, when these trucks' stock cooling system is in good shape and there are no peripheral problems, they just don't overheat. If installing an electric fan is just what you want to do, that's fine. There are certainly worse things you could do. But just know that it is not a necessity to keep it running cool.

[Stocker]

Originally Posted by 70k52wd

I'll try to explain a clutch as it was explained to me.
Clutch is oil filled. This is simplified, but as the rpm is low(idle) the oil gathers near the hub creating the fan to be fully engaged, as rpm increases, the oil spreads out to outer vein perimeter thus disengaging the clutch. Make sense?

I'll add that better fan clutches are thermostatically controlled and filled with a temperature-sensitive silicon fluid. As the temp rises, the viscosity of the fluid increases, engaging the fan.

[Devil Pup]

Originally Posted by mclairmo

I guess nobody is reading my posts, but I will try one more time since I can sympathize with heating issues. You say you went to aluminum pulleys. These are almost always underdrive pulleys, which means the crank and water pump pulleys are the same diameter. Oem pulleys usually have the water pump pulley smaller than the crank pulley to obtain the proper ratio to keep the water pump spinning fast enough to move the water through the system. I know you changed these pulleys with the new motor and the old motor overheated with the old pulleys but I still don't know what kind of pulleys you had prior to the rebuilt motor. I would suggest that you use a smaller water pump pulley, about 6 inches or less in diameter, and a larger crank pulley, as close to 8 inches as you can find. At least you will then have optimized the water pump rotation speed.

sorry sir, meant to respond back to that. the pullys i had on it were stock and then i replaced them with the same diameter just aluminum and dual so i could run two belts. everyone else, i def appreciate all the feed back and would like you guys to give me your opinion on the fans that they recommend because i have the spare funds to just go electric and heard that it would cool a bit better. although i am open to clutch options if anyone can show me. would a pic of the motor and fan set up help at all?
http://www.jegs.com/i/JEGS/555/52116/10002/-1

[69 longhorn]

Devil Pup,how hot does it get in you "neck of the woods"? I am in the middle of Illinois(west boarder), & we see 95-100 degrees F on the hottest days. My old longhorn is running a mildly warmed 383, 4 row core, with dual elect fans. its all fabbed, 2 -14" flex a lites on a damn steel shelf for a shroud. I run painless controls to switch the fans, (185 on/165 off). The truck runs a 160 high flow Robert shaw stat, stock pump, & will sit & idle all day long & NEVER bust 190 on the temp. I think all these guys have some good ideas(tryin to sort it all)LOL! At any rate, problems @ idle , or low speeds in town are usually due to air flow (lack of). Problems @ highway speed are more due to flow on the radiator as a rule. As already mentioned, you really dont need the fan @ highway speed. You can , (as already mentioned) , play with the pullies. Overdrive the waterpump, & that will help you in stop /go traffic,as it speeds up the flow on the coolant, & pulls just a tad more air through the radiator. If you do opt for elect fans, you want PULLERS, as they are more efficient than the pushers that you would mount on the front side of the radiator. One other thought, if the "mill" is real fresh(tight), you may generate a little more heat till she breaks in(200-210 isnt bad in town)......more than that, I get a little nervous. also, tune can play into the game....is it possible that you are a little lean on the new combo,or timing is not quite optimized? can you list out the specs on you engine(comp ratio,cam,carb, total timing,ect? best of luck,crazyAl

[Devil Pup]

Hey longhorn, i live in Tucson, so it gets up about 100 alot of the time. and i also live in Riverside, Ca which often hits well over 100. my truck cant even begin to idle when its hot outside, pretty much the first light i stop at it spikes to 230 and will keep climbing if i dont hit the heater on. i really couldnt list the specs to be honest. its just a stock 5.7 with an RV cam in it. timing was set by a shop and carb was tuned as well. would it be a good idea to have someone re do this? and those fans that im looking for are pullers. so hopefully those would work

Here's a pic of the pulleys/fan. excuse the dirt please lol. havent had much time with the 12 hour shifts ive been working.

[69 longhorn]

Looking at the pullies, it looks like you are about 1 to 1 ratio. This has already been mentioned, but I would also try to overdrive the waterpump(smaller pulley top & larger on the bottom)....see if that helps. does it run cool @ highway speed?

[Devil Pup]

Originally Posted by 69 longhorn

Looking at the pullies, it looks like you are about 1 to 1 ratio. This has already been mentioned, but I would also try to overdrive the waterpump(smaller pulley top & larger on the bottom)....see if that helps. does it run cool @ highway speed?

no it gets hot then as well

[piecesparts]

Let's go back to the first input on ths thread. You stated that you put in a new radiator, new pulleys, new engine, and you claim the system is pumping properly. The first engine blew up due to the heat, so you understand that the proplem was there before the change out of the engine. Now you have put in a set of aluminum pulleys that are the same size as before and have removed the T/stat. I would think that there has to be something that you have NOT changed that is causing the problem, since it is still present with your new setup.

Do you believe that the air flow through your radiator is good? You stated that you have a cooler for your tranny and an A/C coil up front, have you verified that the fins are clean and letting air through them to your radiator? I have an 84 truck with a stroker motor along with a tranny cooler and A/C coil with basically the same pulleys that you are running and I do not have an issue with the cooling. I used to run a standard radiator with a stock fan connected to the water pump. I now run an aluminum radiator with a set of electric fans from "BeCool" and they work great. The change was my choice, since the system was cooling properly prior to the change. I definitely would look at the coils in front of the radiator and make sure that you are getting air into the core. I would also look for ANY place that air could be "short circuiting" the radiator and not going through the fins for cooling. In other words, is it coming from behind the radiator and feeding into the fan? If the shroud is gapped improperly, that could cause this. Put at least a 180 degree T/stat in (that is what I run with no issue, but the 195 will work also). The problem is inside the engine bay and not inside the engine, it has to be part of the truck's setup--since the problem has not changed with the updates that you have performed.

[piecesparts]

There IS something that we have NOT talked about, yet. What is your timing set at on the engine? If you are running retarded too much, the eninge wioll run hot and not perform well. also, it could have been your reason for the last engine's death. just a thought.....

[Stocker]

Oops -- edited for a bonehead mistake....

[Devil Pup]

the fins on the ac cooler are fresh and still as clean as can be, the tranny cooler is as well. so i need to check the gap in the fan shroud for sure and put a T-stat in it. and to be honest i have no clue what the timing is at

[highperf4x4]

A thermostat does not make your engine run any cooler. You can throw that out of your mind right off the bat and narrow down your stressors. The sole purpose of a thermostat is to bring your engine up to an acceptable temperature as quickly as possible to reduce carbon buildup. That's it. If you're running a gen1 engine then your motto is "cooler is better". If you want to run anything higher than a 165 then go ahead but it will not help your motor cool whatsoever. It will simply get to that temperature faster. Thermostats are cheap so you buy one of each and test it yourself. If your engine is overheating it will be the same no matter what thermostat is in it.

Likewise, a clutch fan is not going to improve your cooling much either. A flex fan is designed to flatten the blades at higher rpm's to reduce the strain on your engine and improve gas mileage. The flex fan will pull the most air at lower rpms where you need it. The same is true for a clutch fan however, when the ambient temperature is higher, a clutch fan will not "release" at higher rpms.

Your 3 core radiator should be sufficient to cool your engine provided that it isn't rediculously high on compression like 10:1. If your timing is slow or your fuel is too lean it will make your engine run slightly hotter but it's barely noticeable in stock engines.

All I can do is offer you some questions to consider.

1. Is your A/C properly charged with freeon? Your condensor will heat the air coming through your radiator and if the system is over charged then the condensor will be extremely hot. In fact, it will burn your hand if you touch it.

2. What type of heads/head gaskets are you running on your current engine? When you say the engine continues to run hot at highway speeds it leads me to suspect the heads.

3. Are you sure your water pump is not reversed for a serpentine belt system?

4. Are you sure your flex fan is not a reversed blade fan?

5. Is the crossover for coolant in your intake manifold blocked off?

6. What is your heater core setup? If you still have the factory inline valve to stop the flow of water through the heater core is it getting enough vacum to close it? You can buy a manual valve and install it in the line going from your intake to the heater core to shut off the flow of water in the summertime. Water that flows from the engine to the heater core gets dumped back into the radiator on the same side as the lower suction hose for your water pump. Therefore, it bypasses the radiator core and goes right back into the engine at nearly the same temperature as it came out. I had to install the manual vavle in mine.

7. Where is the sending unit for your temperature guage located? Is it mounted in the head or the intake? Have you let a mechanic check the temp of your engine with a digital gun while your guage says it's overheating?


You biggest ally is more water. If you can't resolve the issue you can always go to a 4 core radiator. It's a problem solver for many issues. If it were me, I'd spend the money on the 4 core before I'd invest it in electric fans. The fans will only help you if your problem is airflow and they won't be all that much better than the flex fan you have now. If you say the fins on your radiator/Condenser/Tranny cooler are in good shape and you're running the proper fan shroud then your problem is not air flow unless your fan blades are reversed.


These are just my thoughts based on experience and no disrespect is intended to anyone that's posted before me. Hopefully something I offered will help and goodluck with it.

[capev86]

i plan to upgrade from a 2 row to a 4 row radiator and run a 180 deg thermostat. 195 is good for a lightly worked car or a truck in a cold climate. will also stick with the stock fan or the nice flex blade i got lying around with the stock shroud. this will be cooling a 406sbc (block and heads crossdrilled) and might try to adapt the trans cooler portion of the radiator for use as an engine oil cooler. figure i want all i can get for durability and protection while towing. i don't have a/c and no plans to add it, so that is one engine load i don't have to worry about.

[Devil Pup]

Hey high perf. thanks for the suggestions, i dont believe my fan is reversible. how would i tell? and yes they checked it with a heat gun and it gets to the temp that the gauge reads off of the block right at the driver side by the exhaust. i do know when i first charged the ac there was too much in it but we released it and recharged it to the proper amount. would you recommend looking into that again?

also a member prior recomended using 100% distilled water with some wetter water because i live in AZ. "not much freezing goin on here" what does everyone else think?

[highperf4x4]

Your fan won't be reversible but you could have a "reversed blade" fan. Does that make sense? In other words, you can get a flex fan for a serpentine belt system like the one I have in my 4x4 and the blades are backwards because it's a reversed rotation fan. As long as your fan is pulling air through the radiator and not trying to push it out the front then you're ok.

As for the freeon, I would definitely check it agian. If you switched the system over to 134a then you should have only charged it to 80% of the capacity it called for with the R12.

What I see so far is this.
You have a new 3 core radiator, condensor, tranny cooler that are all in good shape to allow plenty of air flow.
You have the proper fan shroud.
Your fan is in the right location and doesn't have a clutch.
Your sending unit is in the proper location
Your gauge is reading accurately.
You don't have a stuck thermostat.
Your water pump is new.

That leaves me with the impression that you have a problem either internally in the engine like the wrong head gaskets, an A/C condensor that's getting too hot, water flowing through your heater core and back into the engine, or a very high compression ratio.

As for the water wetter, it will help some but you need to make sure you flush ALL of the antifreeze out of your system first. They are not compatible. However, I would switch it back to a 50/50 mix for winter.

[Stocker]

Is that a flex fan (pic in post #36 above) or a fixed-blade? I can't tell for sure...

Originally Posted by highperf4x4

Likewise, a clutch fan is not going to improve your cooling much either. A flex fan is designed to flatten the blades at higher rpm's to reduce the strain on your engine and improve gas mileage. The flex fan will pull the most air at lower rpms where you need it. The same is true for a clutch fan however, when the ambient temperature is higher, a clutch fan will not "release" at higher rpms.

Great post, but I disagree with this statement.... My truck has never run hot with a clutch fan, but consistently overheated during the brief time I ran a flex fan. And yes, it was the correct flex fan for my truck. As to a clutch fan 'releasing' at higher RPM in high ambient temps, it should -- unless the coolant temp is too high. This is based on experience with my truck and various work trucks over many years.

Originally Posted by highperf4x4

You biggest ally is more water.

Yes, and I can't recall if it's been mentioned, but a closed system with a recovery tank will help a bit, since the system will be completely full of coolant at all times.

Originally Posted by highperf4x4

As for the water wetter, it will help some but you need to make sure you flush ALL of the antifreeze out of your system first. They are not compatible. However, I would switch it back to a 50/50 mix for winter.

http://www.redlineoil.com/Products.aspx?pcid=10
* Reduces or eliminates bubbles or vapor barrier that form on hot metal surfaces to reduce coolant temperatures by up to 20°
* Superior heat transfer properties compared to glycol-based antifreeze
* Compatible with new or used antifreeze (including DEX-COOL and long-life versions) to improve the heat transfer of ethylene and propylene glycol systems
* Improves heat transfer and reduces cylinder head temperature



Was there a reply yet as to the fit (gaps) of the fan shroud?

[Sinister]

Originally Posted by Devil Pup

... and to be honest i have no clue what the timing is at

Set the timing before you start throwing money at it.

[piecesparts]

Have you checked your radiator cap, for proper operation? If it is bad, then there will be no pressure buildup in the core and overheating will happen.

[ERASER5]

I would never recommend straight water for a daily driver. Antifreeze is also Anti-boil. The many ingredients in antifreeze both lower the freeze point and raise the boiling point. A 50/50 mix is not the absolute best mixture, but is the easiest to obtain. Just check the mixture with a hydrometer. The good range is quite large.

As for water wetter, some are better than others. Some cannot be used with glycol and some can. But if you are actually overheating, water wetter will not fix the problem.

Check you radiator cap or just replace it. Caps range from about 7psi to 17psi. I like the 7psi cap myself. More pressure raises the boiling point, but also pushes on the radiator and all the hoses. I like to reduce the stress when I can.