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Old 10-01-2012, 05:49 AM   #11
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It looks like its gonna be the starter. I think it took longer to get that starter off than to diagnose the problem. After 25 years those bolts did not wanna budge, but its out now. Thanks all again for your input.
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Old 10-01-2012, 11:39 AM   #12
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Originally Posted by LobstahClaw View Post


The radiator cap doesn't build pressure.

It's simply an over pressure relief valve.

T & P relief valves are very common safety devices. Just look on your boiler or water heater. You also find them on hot water coils.

They're built into the top of every propane tank you use.

They're also used in private & municipal fresh water systems. That way if there's a failure in the pressure switch your pipes don't get blown apart.
I agree with you on the cap acting as a safety valve but...

How a Radiator Cap Works
The antifreeze and water mixture in your car's radiator is like any other type of liquid and has a boiling point. When any type of liquid is exposed to heat and reaches its boiling point, the liquid begins to evaporate. By placing a liquid inside of a pressurized container, you can considerably raise its boiling point. This is exactly what a radiator cap does for the antifreeze and water mixture in your car's cooling system—it raises the boiling point.
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Old 10-01-2012, 06:19 PM   #13
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Quote:
Originally Posted by 13Harleyfan
I agree with you on the cap acting as a safety valve but...

How a Radiator Cap Works
The antifreeze and water mixture in your car's radiator is like any other type of liquid and has a boiling point. When any type of liquid is exposed to heat and reaches its boiling point, the liquid begins to evaporate. By placing a liquid inside of a pressurized container, you can considerably raise its boiling point. This is exactly what a radiator cap does for the antifreeze and water mixture in your car's cooling system—it raises the boiling point.
The container as a seals unit ( radiator, block hoses etc ) maintains internal pressure. The expansion of water as it heats creates the pressure. The radiator cap simply provides a relief point. If you removed the cap an sealed the filler, by welding it shut for example, it would still be pressurized , thus raising boiling point. The next weakest point in the system would then act as the relief valve and release pressure when it got too high. Most likely a freeze plug or hose would fail and release pressure. The cap itself provides no pressure, only release.
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Old 10-01-2012, 07:36 PM   #14
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Interesting topic.

With the cap in place it's a closed system that builds to a pre-set pressure. That pre set is the rating on the cap.

As the liquid in the engine warms it expands and creates volume and pressure. At the set point the pressure valve built into the cap opens and allows coolant to flow into the reservoir.

As the engine cools it creates a vacuum and the fluid in the reservoir gets sucked back into the radiator.

The boiling point is irrelevent to what we're talking about because the thermostat maintains a pre set temperature. Most of the thermostats open at 180 degrees ? That's well below the boiling of a 50/50 mix.

What i was concerned about was answering the question of why the pressure was allowed to build in the OP's motor to a point where it could blow a hose off the radiator.

One of the clues that the serpentine belt may have failed in some way was that the power steering went out. The belt is the one common thing shared between the cooling system, the charging system, and the power steering system.

Who knows .... half the time it's guesswork at best.
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Old 10-01-2012, 09:22 PM   #15
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Quote:
Originally Posted by LobstahClaw
Interesting topic.

With the cap in place it's a closed system that builds to a pre-set pressure. That pre set is the rating on the cap.

As the liquid in the engine warms it expands and creates volume and pressure. At the set point the pressure valve built into the cap opens and allows coolant to flow into the reservoir.

As the engine cools it creates a vacuum and the fluid in the reservoir gets sucked back into the radiator.

The boiling point is irrelevent to what we're talking about because the thermostat maintains a pre set temperature. Most of the thermostats open at 180 degrees ? That's well below the boiling of a 50/50 mix.

What i was concerned about was answering the question of why the pressure was allowed to build in the OP's motor to a point where it could blow a hose off the radiator.

One of the clues that the serpentine belt may have failed in some way was that the power steering went out. The belt is the one common thing shared between the cooling system, the charging system, and the power steering system.

Who knows .... half the time it's guesswork at best.
Your exactly right. If the cap fails to relieve pressure it will continue to build until something else gives. Along that line the overflow tube could be plugged.
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Old 10-10-2012, 12:43 AM   #16
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Question question about overflow tank

Ok, I understand how the cap works, etc. I am wondering if the overflow tank has some sort of valve on it, and if so, is it on the bottom, or built in? It looks like the coolant in my overflow tank never runs out, and nothing ever runs into the tank. How can I check it? Surely, somewhere along the way, there would be movement in or out, especially after driving a long way in stop n go traffic. Thanks.
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Old 10-10-2012, 08:50 AM   #17
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When the tank boils over that's where your coolsnt goes before the cap pops. Also when it cools down low it sucks fluid out of there to fill the radiator.
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It's just stiff and hard
Lube will always help this
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Old 10-10-2012, 03:43 PM   #18
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There is no check valve in the tank and its cap isn't strong enough to hold pressure so you should be fine there. You may as well clean it out while you are at it though.
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Old 10-10-2012, 07:54 PM   #19
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There is no check valve in the tank and its cap isn't strong enough to hold pressure so you should be fine there. You may as well clean it out while you are at it though.
Definately. Clean the tank, make sure the overflow tube is clear, and change the radiator cap out on a regular basis.

I learned about the radiator caps being a regular maintenance item the hard way when the top of the radiator on my E-150 blew right off the core.

It wasn't much fun to have to solder it back in place.
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Old 10-10-2012, 08:12 PM   #20
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Ok, I understand how the cap works, etc. I am wondering if the overflow tank has some sort of valve on it, and if so, is it on the bottom, or built in? It looks like the coolant in my overflow tank never runs out, and nothing ever runs into the tank. How can I check it? Surely, somewhere along the way, there would be movement in or out, especially after driving a long way in stop n go traffic. Thanks.
It gets into the nitty gritty of things.

I don't know about other motors but on my 300/6 the rule of thumb when you were refilling the radiator was to leave the level 1 inch low.

As long as the cooling system is working the way it's supposed to that 1" air space at the top of the closed system acts a compressible "pillow" to accomodate normal expansion and contraction due to changes in temperature.

The radiator cap really is more of a safety devise than anything else for when something isn't right.

ie: You didn't leave that air space & overfilled your radiator. The cap allows the extra coolant to flow into the reservoir.

ie: You've got a small leak somewhere in the system and the engine is consuming 1/2 pint every 5,000 miles.

The cap allows the cooling system to draw in some "make up" up coolant from the reservoir to top it off to the correct level as it's needed.

It's kind of a neat design really. More for safety and environmental protection than anything else. Back in the day most vehicles didn't have a reservoir so if you did happen to overfill your radiator the excess would just dump on the ground.

Your dog or cat would come along and lick up that sweet tasting puddle under the truck and get poisoned.

Last edited by LobstahClaw; 10-10-2012 at 08:14 PM. Reason: typos
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Old 10-10-2012, 08:12 PM
 
 
 
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