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Author
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Topic: What is the best way to flush the cooling system?
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BaLleRz68
Gearhead Posts: 113
From: Bay Area, CA
Registered: Aug 2002
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posted 12-19-2002 04:17 AM
 
I took my radiator off because it has a leak on the top and its getting fixed. What is the best way to flush the cooling system? Can I stick a water hose inside top radiator house and let it drain to the bottom hose until I see clear water? Can I do this while the car is running? Are there any precautions I should take? Any thoughts are appreciated. THanks.
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Fastback68
Gearhead Posts: 4511
From: Sucat, Paranaque, Philippines
Registered: Jul 99
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posted 12-19-2002 05:54 AM
You're a little off target  Grab a bottle of radiator flush from your local gas station, and it should have the instructions on the bottle. You add it to your radiator, run the engine, detach the lower hose, and see how it looks. If it's still cruddy, you do it again.
Now if you're engine's seriously filled with crud (which means you probably have an overheating problem), there's a whole more dramatic approach.
And once you're done, fill up with distilled water, not tap water, especially if you have hard water in your neighborhood.
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cobravenom71
Gearhead Posts: 1349
From: Poinciana, Fl USA
Registered: Aug 2002
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posted 12-19-2002 08:27 AM
I've been using the 'Flush N' Fill' kits for years. You know, the ones that you splice a 'T' into the heater inlet hose? Those have always seemed to work very well for me.
I don't see a lot of people using them much lately, though. Is there a problem with using them that I don't know about?
I have never had a problem using one, and it always seems to get a LOT of crud and rust out, even when the 'sample' from the top of the radiator appears 'clean'.------------------
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69 Sportsroof
Gearhead Posts: 2814
From: Valley, Alabama, USA
Registered: Mar 2002
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posted 12-19-2002 08:40 AM
According to my local radiator shop, when the seam around the tank starts leaking, its almost impossible to effectively repair it. It seems that they can replace a core but not the tank. I just had mine worked on and the shop recommended I use a 7 lb cap instead of the 13 lb and I should be able to make it through winter before I have to replace the radiator.
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SteveLaRiviere
Administrator Posts: 48752
From: Saco, Maine
Registered: May 99
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posted 12-19-2002 08:59 AM
The Prestone stuff works great. Sometimes too good if crud is plugging a leak.------------------
'70 Mustang Mach 1 - '72 Mustang Sprint - '94 F-150 Be sure to remember our sponsors, Mustangs Plus, NPD, and Osborn Reproductions.
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V8 Thumper
Gearhead Posts: 4777
From: Phoenix, Arizona
Registered: Dec 2001
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posted 12-19-2002 09:14 AM
Ditto on the 'flush and fill' kits and the Prestone flush treatment. Read the directions carefully... it's pretty mean stuff and is only meant to be ran for 15 minutes before flushing.As far as radiator caps go, I too run a 7# cap. One psi equals a two degree raise in the boiling point; 13# cap would raise the boiling point of straight water to 238, a 50/50 mix of coolant/water would put it in the 250 range  Do you ever intend on running your motor anywhere near 220, let alone 250? All that pressure isn't necessary, it just taxex your gaskets/radiator/heater core/fittings/hoses ------------------
1965 GT coupe, 333ci aluminum headed/solid cammed stroker, four speed, 3.70:1 9" All Blue Oval, no blue bottle
http://mustangsandmore.50megs.com/V8Thumper.html
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cobravenom71
Gearhead Posts: 1349
From: Poinciana, Fl USA
Registered: Aug 2002
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posted 12-19-2002 12:59 PM
There's a a little confusion on the radiator cap pressure issue. It is true that a higher pressure cap will allow the boiling point of a fluid to be raised, which is reffered to as the 'latent heat of vaporization'.
However, a higher pressure cap does not raise the temperature of your engine. In fact, it does just the opposite!
If a lower pressure cap is used, the total amount of heat that your coolant can hold, and therefore carry away from your engine is lower.This means that your engine cannot release as much heat into the coolant, since it is already 'full'. Hence, a hotter running engine.
A higher pressure cap raises the boiling point (vaporization point) of the coolant. Since a liquid can continue to absorb heat until it begins to vaporize, a fluid held under pressure can 'hold' more heat on its way to the radiator.
Otherwise, we would all just run 0-pressure caps!
Of course, higher pressure-caps do put exra strain on the entire cooling system, so make sure that yours is in adequate shape. ------------------
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Fastback68
Gearhead Posts: 4511
From: Sucat, Paranaque, Philippines
Registered: Jul 99
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posted 12-19-2002 08:12 PM
Cobravenom, maybe I've misunderstood you, but I think you're reading something into the way rad caps work that might not be there.
As I understand it, a radiator with a low pressure cap can hold exactly the same amount of heat as a radiator with a high pressure cap, right up to the point where the cap blows. A high pressure cap simply allows you to run your engine hotter, and as V8 Thumper is saying (I believe), it's better to have your rad cap blow than run your engine too hot.
Are we all on the same page? Or are we saying different things?
Simon
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Fastymz
Moderator Posts: 22791
From: Reno Nv M&M #1240
Registered: Apr 2001
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posted 12-19-2002 08:26 PM
The flush and fill kit,I do my alittle different.Rather then cut and splice my heater hose.I just disconect the heater hose.And plug the flush and fill fitting one end and a short piece of heater hose on the other.That way I dont have to leave the flush and fill fitting on my heater hose.I've read that the Ford DIESEL flush works real well.Anyone every hear this or used it. SCOOP ------------------
oddly obsessed with big scoops on little Mustangs 2.26 60'S
14.9 @ 90.86MPH 65 coupe,351w,C4,Big Boss 429 hood scoop,8"3.40 TracLoc,Cragar SS,Black Suede. https://mustangsandmore.com/ubb/Fastymz.html
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cobravenom71
Gearhead Posts: 1349
From: Poinciana, Fl USA
Registered: Aug 2002
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posted 12-19-2002 09:34 PM
OK, here we go... The boiling point of water at sea level(ambient pressure) is 212 degress. That simply means that water can be heated until it reachs 212 degress, at which point it will begin to vaporize (boil).
Upon vaporization, a fluid will release any stored heat. The water has now changed from a liquid state into a gaseous state. This is known as the 'Latent heat of vaporization' law. This phenomonon is what the basics of refrigeration and air conditioning are based on.
As the vaporized liquid (gas) molecules release the stored up heat, they will cool, and when they reach the temperature of the surrounding medium (air), they begin to condense back into a liquid state. This is the nature of dew on the grass in the morning, and liquid on the outside of a cold glass of ice tea on a hot day.
By increasing the pressure placed upon a liquid, you are raising the point at which it will vaporize. This is because as the liquid's molecules move farther apart from one another as they heat up, they exert more pressure on the surrounding atmospheric contra-pressure(ambient).
When the liquid is pressurized, it's molecules try to expand and 'push' harder
against the surrounding higher contra-pressure before it's molecules 'burst'. This is the boiling point, technically known as vaporization.
A liquid will continue to absorb and hold heat until it reaches it's vaporization point.
For every pound above ambient (at sea level) the boiling point of water is raised by 3 degress. Therefore, a 16-pound cap will increase the boiling point of the water by 48 degrees, to a total of 260 degrees.
Now, if you have a 160 degree thermostat, that does not mean that your engine is operating at 160 degrees. It means that your COOLANT is operating at 160 degrees.
With a 7 pound cap, your cooling system would be capable of 'holding' approximately 233 degrees of heat before it will begin to spontaneously release it. This is what the overflow/recovery bottles are for. As it vaporizes, it leaves the system in the form of steam and goes to the overflow, where it condenses back into a liquid, and is then drawn back into the system when it cools to the same temperature.
There are many areas of a typical engine that get much hotter than 250 degrees, but our temperature gauges are measuring the temp of the coolant at only one specific point in the engine, not the engine itself.
Your engine is going to produce the same amount of heat no matter what pressure cap you use, even if you use no cap. The point is, how do we get rid of that heat. The difference is that with ambient or a low pressure cap,the total amount of heat that can transfer into the coolant and out of the engine's materials is low. this is because the coolant is not capable of holding any more heat.
A higher pressure cap allows the coolant to hold more total heat,which in turn allows the engine's materials to 'dump-off' more heat in the same amount of fluid.
This extra heat is obviously carried to the radiator where the heat is released to the surrounding atmosphere.
This is why a radiator that is hot will be fine as long as the cap is not removed. The pressurized 'atmosphere' inside the radiator is 'squeezing' the coolant molecules tight, which keeps it from vaporizing (boiling).
If this cap was removed from a hot radiator, the atmospheric pressure drops from high to ambient immediately, and the high pressure molecules of the hot coolant suddenly have no resistance to thier natural tendancy for expansion. They will violently expand(vaporize), and the now-boiling coolant will look for the easiest path of least resistance which is the open radiator fill.
So, a higher pressure cap does not raise the operating temperature of the engine. It only raises the total amount of heat that a cooling system can effectively remove from an engine.
A low pressure cap gives the coolant less ability to hold heat, so the engine itself will 'store' this heat until it can find another source of release.(pistons, connecting rods, oil etc...)
But, if your particular vehicle can operate effectively with a 7 pound cap, then that means that the coolant is carrying away a sufficient amount of heat. Otherwise the coolant would vaporize, and the engine would overheat. Under these circumstances, there would be no need to use a higher-pressure cap, as it would put unnecessary strain on the cooling system componenets.
Yet, if you have a relatively powerful, high-compression engine, a low pressure cap will probably not be sufficient, as these types of engines produce a lot of heat.
Many, many people make the fundamental mistake of thinking that a bigger radiator is all that is needed to keep a hot-running engine cool. Thier flawed logic goes something like this: 'More coolant can hold more heat, plus the larger radiator puts more coolant in front of the air-flow so it can release more heat to the atmosphere.'
While it is true that a larger radiator will handle more heat, that difference alone is so miniscule as to be almost inneffective. Here's why: Remember, the medium of transfer is the coolant itself, and if the coolant cannot hold enough heat and take it to the radiator, then the radiator will never have a chance to utilize its capacity. You gotta' GET the heat to the radiator before it can do its job. A low pressure system will only take the amount of heat it can hold to the radiator. If the radiator never 'recieves' the heat in the first place, it has limited ability to release it. This is why you will see many street rods with HUGE radiators, a couple of fans that are ALWAYS running, and they still seem to overheat.
This is also why newer cars from the factory (especially jap cars) can use such tiny radiators without ever overheating. Thier system is designed to remove the maximum amount of heat from the engine, and the radiator is designed to handle JUST THAT MUCH heat transfer. ------------------
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steve'66
Gearhead Posts: 9835
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 12-19-2002 09:46 PM
cobravenom71,Thanks for that thesis on radiator cooling, it was well done and took a lot of effort. Well done,
SteveW
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steve'66
Gearhead Posts: 9835
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 12-19-2002 09:49 PM
quote:
Originally posted by 69 Sportsroof:
According to my local radiator shop, when the seam around the tank starts leaking, its almost impossible to effectively repair it.
I've got a radiator in my fleet that leaks at the upper tank's seam. Does that mean I should just buy it a new radiator? The radiator is only 3-4 years old.  SteveW
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69 Sportsroof
Gearhead Posts: 2814
From: Valley, Alabama, USA
Registered: Mar 2002
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posted 12-20-2002 10:37 AM
quote:
Originally posted by steve'66:
I've got a radiator in my fleet that leaks at the upper tank's seam. Does that mean I should just buy it a new radiator? The radiator is only 3-4 years old. SteveW
According to the radiator shop I use the answer is maybe. He said that usually the repair wont hold up. If it does, that's great. If not, you're gonna have to cough up about 2 bills.
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Fastback68
Gearhead Posts: 4511
From: Sucat, Paranaque, Philippines
Registered: Jul 99
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posted 12-20-2002 12:11 PM
Hmmm, a good repair is certainly not rocket science.
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