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454 Overheating Problem

fmstruck said:
Huh?
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You're right that is completely not true. The typical engine water pump cannot create any significant pressure. In fact, flow will fall off exponentially as pressure(from one side of the pump to the other) as pressure increases. Which is why when the thermostat closes flow falls to almost nothing (except for the bypass passages to keep a little water moving to remove hotspots).

The pressure is created from the coolant heating up, which is why the radiator cap (which happens to be on the suction side of the pump, and there is still pressure) releaves the pressure into the reserve tank so pressure does not get excessive.

The water restrictors restrict flow so that it doesn't run too cool. They work good for consitant operations but are independent of ambient air temp. So the engine will run cooler on cooler days.

And taking a thermostat out cannot make an engine run hot unless there is some other problem. There is no way the coolant can go through the radiator too fast, that is a myth. If the radiator can remove heat faster than the engine can make it, (which it has too or it would overheat anyway), then removing the thermostat will only make it run cooler, and it will run even cooler in cooler temps. You just change the rate of coolant temp difference. You may have a lot more flow and the temp of the water flowing through the radiator may be only slight less than the engine temp, but it will be constantly flowing a LOT of water, removing a little heat per gallon with a lot of gallons, and therefore still remove the heat. If you restrict the flow in the radiator to get it too cool down more then the engine will at the same time be heating up more.

I still say hook up your vacuum advance to full manifold vacuum if you haven't. And yes, you might need a bigger radiator. And you need to make sure your fans are shrouded correctly.
 
We've beaten this to death before. Never going to resolve it apparently. Some engines run hot with no thermostat, some run cold. My experience has been cold.

"A common misconception is that if coolant flows too quickly through the system, that it will not have time to cool properly. However the cooling system is a closed loop, so if you are keeping the coolant in the radiator longer to allow it to cool, you are also allowing it to stay in the engine longer, which increases coolant temperatures. Coolant in the engine will actually boil away from critical heat areas within the cooling system if not forced through the cooling system at a sufficiently high velocity. This situation is a common cause of so-called "hot spots", which can lead to failures.</SPAN>

Years ago, cars used low pressure radiator caps with upright-style radiators. At high RPM, the water pump pressure would overcome the radiator cap's rating and force coolant out, resulting in an overheated engine. Many enthusiasts mistakenly believed that these situations were caused because the coolant was flowing through the radiator so quickly, that it did not have time to cool. Using restrictors or slowing water pump speed prevented the coolant from being forced out, and allowed the engine to run cooler. However, cars built in the past thirty years have used cross flow radiators that position the radiator cap on the low pressure (suction) side of the system. This type of system does not subject the radiator cap to pressure from the water pump, so it benefits from maximizing coolant flow, not restricting it."

http://www.stewartcomponents.com/tech_tips/Tech_Tips_3.htm

"On traditional flow configurations the block is pressurized by the water pump and functions as a manifold. The head gasket distributes the coolant through it's orifices. Block pressure must be consistent from front to rear to insure uniform coolant distribution. Low pressure will results in less flow around the rear cylinders. "

http://www.stewartcomponents.com/tech_tips/Tech_Tips_6.htm

"Extensive testing with our in-house water pump dyno system, has resulted in achieving best flow, block pressure with the least amount of shaft consumption."

http://www.adamspumps.com/index.html

"Special impeller and tight clearances provide increased coolant flow, block pressure, and balanced delivery."

http://www.edelbrock.com/automotive_new/misc/company/pdf/water_pumps.pdf

"I have used a ten gallon portable air in two of my cars. Costs about 30$ at the auto supply. We set up the return to tank (two # 10 hoses .. one from each head) to restrict water flow so that at about 5000 rpm the block is pressured to about 20 psi."

http://www.landracing.com/forum/index.php?topic=6217.0

Look at antifreeze. It's "common knowledge" that you need it to keep your engine cool. And completely false. Coolant can't move upwards (against gravity, since the water pump isn't higher than the upper hose) if pressure isn't being built with the water pump.
 
Obviously the pump needs to create a pressure differential to move coolant. Not arguing that fact. A friend of mine ran a pressure gauge and a light on his IMCA modified because he wanted to know what was going on in the system. He always ran a thermostat and said that the pressure wouldn't even turn off his light (which was activated by a low oil psi sender 5-7psi)when the engine was first started unless you wound the crap out of it. While racing and at temperature, the pressure gauge would fluctuate, but never exceeded cap pressure. The gauge was located right next to the thermostat on the high pressure side.
 
Just a thought that hasn'tbeen mentioned and COULD be an issue. Has the OP checked to see if the radiator fins are clean of caked mud, bugs and excessive oil leakage from a tranny cooler getting onto the radiator. Maybe it's just a matter of cleaning up the front and the inside part of the fins from debris. hard for a fan setup to pull air throught a clogged, uncleaned radiator and idle or slow speeds as opposed to air being forced throught the radiator at higher speeds.
 
I know for a fact that I saw somewhere a listing of block pressures that showed 40PSI. Can I find it? Nope. :)

I will freely acknowledge however, that "taking" 3-5HP (which are the numbers I see listed for most pumps) to turn at high RPM leads me to believe that the pump can't be making much pressure, otherwise power consumption would be much higher.
But, all that said, we are back to the thermostat/restrictors, which some are going to choose need to be in place to make the coolant work.

Thermaldynamics say othewise. The hotter coolant gets, the worse it works. The longer coolant is in contact with the cylinder walls, the hotter it gets, the worse it cools, and it WILL boil, which means the engine is not getting cooled as it should. So yes, the restrictor makers are wrong.

Obviously orifice diameter will change flow, so the engine temperature can be "set" based on coolant speed through the radiator (which means it will be consistent with X engine/water pump RPM/load). It has nothing to do with absorbing heat efficiently from the cylinders, and everything to do with how fast heat is being lost through the radiator.
 
Dorian I agree with most of the things you said, except for in your first post. :wink1:

I think our ideas of pressure might be different. There needs to be a slight pressure differential or it won't move I agree, but as the pressure differential increases flow falls off exponentially. It's not a high pressure sealed pump, it's a high volume low pressure pump, it only works on the condition that there isn't much restriction, or backpressure, or it won't flow. (try to inflate a tire with a one of those air toy inflators)

I would be shocked if the pump created more than a few psi under most conditions, which is very low compared to the 14 - 20 psi of the system. The pressure is created from the heat.

I agree the restrictor is not needed to make the coolant work. It only restricts flow to reduce cooling, not to create pressure. It will create an equilibrium coolant temp, but that equilibrium temp will vary slight proportional with ambient air temp.

By the way, I am glad you posted those links because they are agreeing opinions of what I am trying to convince some colleagues of that won't believe me. They should help. Thanks :D
 
I believe it was even Stewart where I saw the claim of 40PSI block pressure. I really wish I could find it again, perhaps I took it out of context, for whatever reason I can't find it. Perhaps Stewart made a mistake and I ran with it. :)
 
I've read all the posts. Let me start by saying that most of you seem to have vastly greater mechanical skills than I do. However, if he is getting good temps at speed and overheating at idle etc why wouldnt it be a basic issue? Like I stated in my other post with a clogged radiator on the outside with mud, dirt or oil. Or the inside of the radiator has "gunk" clogging the tubes etc. Is it possible the pully on the pump is the wrong diameter and not allowing the pump to spin fast enough? Does the pump spin the right way?

I'm not understanding the whole pressure thing anyways so maybe that's what's happening. Just seems that if the radiator is cooling sometimes it has got to be a bad/sticky thermostat or radiator.
 
I think some of you are on crack. We have run with and without thermostats and with and without restrictors. The system cools any of the ways. We had a 318 in a challanger that never saw over 140 deg and needed a thermostat to warm up. We run a washer to restrict coolant in the dirt track car but it runs the same either way and just makes the old school driver feel better with it in. It never runs hotter than 175 degrees even after 20 laps at 7200.

If it doesn't cool in town it needs more airflow. My 600hp bbc camaro has 04 impala fans on a cheapy dirt track radiator switched with a chrysler mini van switch and runs 170-180 (where the switch operates) all the time no matter the vehicle speed or temp.
 
Oh and if you look at speedways tips in there catalog they will tell you if you have cylinder pressure (from a bad head gasket) it will expand the tubes of the radiator and stop cooling. If your pump put out 40 psi it would blow off the hoses, the cap and wreck the radiator. Have you ever seen guys try to keep hoses on a turbo system with 20 psi?
 
i personally believe, if they keep going with trying to determine what does what in a cooling system, they are going to be down to the level of telling us what each different molecule in water and coolant chemicals do under certain pressures and temps....
 
4xcrazy said:
i personally believe, if they keep going with trying to determine what does what in a cooling system, they are going to be down to the level of telling us what each different molecule in water and coolant chemicals do under certain pressures and temps....
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qft
 
TIMING, TIMING, TIMING..... That was the problem! A couple of buddies and I did some research here and on the the Net. And we desideed to start out with the timing. It needed to be advanced. But just a little. The radiator was getting cooled but the engine was not. So the dual fans where doing their job. Thank God! (I did not what to go to manual fan. Just because I did alot of Fab work to make my duals work.)
After advancing the time. It almost cooled the engine right away. I have NO overheating problems now. Engine runs between 160 and 175 degrees with a 160 T-stat. All the time! I can not believe I was so close but yet so far!!

But thanks to all of your input. We were able to start from the easiest point first. And it worked!!! Lucky for me. I think I will go buy a lotto thicket. Maybe I can get lucky there to!!!
 
Dude Get out of my Truck. 350tbi new 3core alumin radiator Three new Tstats. 160 degree New water pump same Damn Problems. New Gauge too. Now temp climbs and stays around 170. Yesterday climbed to 240 then all of a sudden 165. driving me Nucken Futz. No fans all stock o and even a new Fan clutch.

simplysigns said:
OK I have check all the threads on overheating and I am going nutts!! So bare with me.

Here is what I have....
Engine....1972 Chevy 454 (came out of a 2wd 3/4 ton truck). Has been rebuilt but nothing crazy. 30 over, Mild cam, heads back to stock, After market aluminum intake, Holly 670 avenger carb, Headers. This engine is 98% new. I have put every hour on it (I installed a hour gauge).

Cooling system.... After market High flow water pump, 3 core Aluminum radiator, 160 degree T-stat, Dual 15" electric fans with a shroud.

Now here is what goes on. Going down the road I have no problems. Gauge stays around 160-180 degrees. It only gets hot on trails and at idle (after 10 or 15 minutes). If I get back on the road. It cools back down. So this tells me it is air flow. Right?

Here is what I have done. Went through 2 T-stats (1 180 degree & 1 160 degree, both do the same). Went through 2 Radiator caps (both good, same). All new hoses (no kinks). Coolent is flowing fine. And there is nothing blocking the grill in front. Everthing is clean. The fans are pulling air through the radiator like crazy. But not enough! WHY????

I did read a post about the timing may be off. Causes overheating. Is this something I should look into? It runs great. I have a small hesitation if I hammer it from stop position. But after that, it runs like a bat out of hell.

Any input is always welcome. So please feel free. At this point I am up for anything!!
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TDAWG1 said:
Yesterday climbed to 240 then all of a sudden 165. driving me Nucken Futz. No fans all stock o and even a new Fan clutch.
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back when mine used to do that, i found it was about a gallon and a half or so low on coolant, that of course is when i later found out is was a leaky headgasket causing the water to go elsewhere too..

ever since the replacement motor went in though, new t-stat and same 4 core rad, it runs at or not much higher than the t-stat.

and BTW 160 t-stat? in a TBI motor? you like burnin the fuel up, don't ya :wink1:
 
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