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  #1  
Old 06-17-2005, 11:12 AM
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Lower Radiator Hose

I am in the process of cleaning out my cooling system with citric acid. I emptied the system, put in the citric acid, filled with water, and took the car for a short drive. Now that I am back home, I was just checking some things under the hood.....

I felt the back of the radiator, and its rather cool to the touch. I also felt both of the radiator hoses. Top hose is nice and hot, but bottom hose is about the same temp as the radiator. Which leads me to my question.....

Should the lower hose be hot like the top hose. Same question for the radiator... Im assuming they should be hot, considering the nature of the cooling system.

If they are supposed to be hot, could that possibly mean that the thermostat is not opening, or not opening enough?

Any help on this would be wonderful.

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Old 06-17-2005, 11:51 AM
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There should always be a temp difference between the top and bottom hoses because the coolant has passed through the heat exchanger from top to bottom, transfering latent heat energy from the coolant into the air. Also, if they aren't working hard, diesels just don't make much heat. A spin around the block (unless you live in San Francisco) probably won't be enough work to cause the thermostat to open much, thus the relative coolness of the lower radiator/hose.
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Old 06-17-2005, 12:41 PM
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Quote:
Originally Posted by superbeast1098
I am in the process of cleaning out my cooling system with citric acid. I emptied the system, put in the citric acid, filled with water, and took the car for a short drive. Now that I am back home, I was just checking some things under the hood.....
When doing the project for the head on the 617, I found something that is very interesting regarding the cooling system. Now, this should be obvious to everyone, but this example really brought it home:

I drained the radiator via the plug in the bottom.

Removed the thermostat and housing.

I'm staring at the hose from the block that is filled up with coolant, right to the top of the hose. So, the entire block, up to the level of the thermostat, is still full of coolant.

So, the only method of removing this coolant is to get under the engine and remove the plug on the side of the block. I probably got another three quarts of fluid from the block.

The reason I mention this is the citric acid flush. If you are using citric acid, be certain that you remove the block plug to drain all of the flush solution from the system. Draining the radiator and refilling is not going to cut it.
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Old 06-17-2005, 06:17 PM
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"Should the lower hose be hot like the top hose. Same question for the radiator... Im assuming they should be hot, considering the nature of the cooling system."

Not if the radiator is working. Hot water goes in the top, and comes out the bottom cool. Of course I use the terms in a relative sense, water coming out the bottom at 150 degrees may be "cool" if the water going in the top is 200 degrees.
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Old 06-17-2005, 06:48 PM
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Well, I also replaced the thermostat while I was working on everything. Now the radiator is hot most of the way down, as it should be. Before, the radiator wouldnt get more than 10 or 15 degrees hotter than the ambient temp outside. The plastic top of the radiator would get very hot though.

I dont know what is going on with this cooling system. I have replaced everything but the fan, fan clutch, and radiator. And the radiator is fairly new, about 3 years old....

Thanks for the help so far..... Any more suggestions, tips or tricks would be wonderful
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Old 06-17-2005, 10:05 PM
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Thats why the lower hoses last forever. The bottom tanks never seem to crack to.
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  #7  
Old 06-18-2005, 05:54 PM
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Super,

The top of the radiator should always be hotter than the bottom because the hot coolant from the engine goes into the top of the radiator, is cooled as it goes thru the radiator and comes out the bottom of the radiator cooler so it can cool the engine.

The temp of the radiator varies with how much heat the engine is generating and if the thermostat is open or closed. So it doesn't tell you much by feeling the radiator. What counts is what the temperature gage says.

P E H

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