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Unread 09-17-2011, 02:22 PM   #1
IrishCJ6
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Top radiator hoses sucks itself together under throttle

Ok so I got the V8 (AMC 360) going yesterday and I have just noticed that when cold the top radiator hose sucks itself together when I give it some quick throttle, as soon as I release it the hose returns to normal, if I slowly apply throttle it doesn't seem to do it????

Anyone have any idea why this is doing this, I thought it may be a air lock somewhere?

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Unread 09-17-2011, 02:38 PM   #2
LimeLite
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Don't know why it's doing it but, do you have the coil inside the hose? It would prevent it from collapsing
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Unread 09-17-2011, 02:44 PM   #3
IrishCJ6
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No I have the genuine GATES hose, cause I never really liked those sprial hoses, good idea though but I would like to know where the vacum pressure is coming from.
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Unread 09-17-2011, 02:52 PM   #4
81azcj7
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Just a thought ..it might have something to do with your radiator cap and the build up and release of pressure.
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Unread 09-17-2011, 04:29 PM   #5
gmakra
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Its really quite simple the OP stated when its cold the thermostat is still closed. When you rev the engine the water pump will try circulate water and with no flow it crates a negative pressure down stream of the thermostat thus collapsing the hose.
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Unread 09-17-2011, 04:52 PM   #6
IrishCJ6
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Ok, sounds possible, but I thought that in the thermostate there is a bypass hole to allow a small amount of water to pass through it therefore stopping this so called negitive pressure, does that mean that this type of thermostate does not have this bypass hole? or does this mean that this bypass hole is blocked?
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Unread 09-17-2011, 05:40 PM   #7
davbytrace
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OK guys, if the system is solid with water, there should be NO decrease in the volume of the container when negative pressure is applied. Simple physics.

Answer: You have air in your system.
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Unread 09-17-2011, 06:31 PM   #8
Nereussailor
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LimeLite posted about the coil inside of the hose, and it kind of got walked around. The 258 has a wire coil inside of the hose that keeps it from colapsing. Not the coil type hose. I'm not sure if the 360 had them, but they were there for a reason. I do agree with davbytrace on the air in the system though. Did you run the motor until the thermostat opened, with the radiator cap off?
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Unread 09-17-2011, 07:45 PM   #9
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Quote:
Originally Posted by gmakra View Post
Its really quite simple the OP stated when its cold the thermostat is still closed. When you rev the engine the water pump will try circulate water and with no flow it crates a negative pressure down stream of the thermostat thus collapsing the hose.
X2

I wouldn't worry about it unless it occurs when warm.
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Unread 09-17-2011, 10:11 PM   #10
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I'm trying to work this out, and I could be wrong, but here goes... the water pump is pulling the water from the radiator, hence the vacuum. The hose isn't rigid enough to keep its shape, thus it collapses. That's why radiator hoses have a spring/coil inside the neck, ... to prevent that. Especially after the water is heated and the rubber becomes softened. I get lost on the vacuum theory of the cooling system! I know you can pressurize the system to check for leaks, but the radiator has a vent hose that goes to an overflow canister, and it is not airtight. So how do you avoid air in the system?
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Unread 09-18-2011, 08:20 AM   #11
Nereussailor
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As long as the hose in the overflow canister is submersed in antifreeze, it shouldn't suck in any air, only more antifreeze.
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Unread 09-18-2011, 08:33 AM   #12
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The system stays solid because the spring on the radiator cap is pressing down on the filler neck seat. When the overflow system is working properly, the slightly higher pressure caused by the hot water will cause the spring to lift slightly. This allows hot pressurized water past the seat into the overflow bottle.

If the bottle has the minimum amount of water always in it (this creates a seal), then the water from overflow will, when the radiator goes to a lower pressure from cooling, travel back to the radiator to refill it. Since the overflow bottle still has the minimum amount of water in it at the end, you never introduced air into the system.

The physics trick here is that you are always keeping a water seal on the system to keep air out. This somewhat analogous to the "P" trap under your kitchen sink that keeps sewer gas from entering your house.
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Unread 09-18-2011, 09:03 AM   #13
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Quote:
Originally Posted by Nereussailor View Post
As long as the hose in the overflow canister is submersed in antifreeze, it shouldn't suck in any air, only more antifreeze.
Quote:
Originally Posted by davbytrace View Post
The system stays solid because the spring on the radiator cap is pressing down on the filler neck seat. When the overflow system is working properly, the slightly higher pressure caused by the hot water will cause the spring to lift slightly. This allows hot pressurized water past the seat into the overflow bottle.

If the bottle has the minimum amount of water always in it (this creates a seal), then the water from overflow will, when the radiator goes to a lower pressure from cooling, travel back to the radiator to refill it. Since the overflow bottle still has the minimum amount of water in it at the end, you never introduced air into the system.

The physics trick here is that you are always keeping a water seal on the system to keep air out. This somewhat analogous to the "P" trap under your kitchen sink that keeps sewer gas from entering your house.
Now that you bring that to light, it's obvious! Thanks for the education... I should have figured that one out.
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Unread 09-18-2011, 09:04 AM   #14
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OK, what's causing the issue,
When you have an old water pump, or when you have a replacment with poorly designed impeller in the pump,
When you hit the throttle, you CAVITATE the water.
The impeller actually rips holes in the water before it can get moving.

When you create those holes (some call them 'Bubbles', but 'Bubbles' are POSITIVE pressure,
These are NEGATIVE pressure holes in the water.

Since there are 'Holes' in the water, that's all that can be forced into the block...

When these holes in the water collapse, they cause a vacuum in the block, and you get your top radiator hose sucked shut...

------------------------------

Now, when you rev up SLOWLY the water can move fast enough to fill the block and circulate without ripping it apart, and you don't get the hoses sucked shut.

(Cost me $5,000 in the early 80's to machine apart blocks and put in lexan windows to watch and understand this, so pay attention unless you have a large milling machine, a 25 horse power electric motor, strobe lights to stop the action, ect. to do your own testing!)

A PROPERLY designed impeller and water pump housing will NOT rip holes in the water...
So you either have a CRAPPY water pump, or your water pump is on it's last legs.

The upper hose is SHOT, when they get spongy, they are SHOT, CHANGE THEM!

There are also metal & plastic springs that go into the hoses to keep the problem you describe from happening...
LOWER HOSES SHOULD ALWAYS HAVE A SPRING!

When a lower hose sucks shut, it dries out the pump for water flow (meaning the water can get into the block faster than the radiator can supply it via the hose).

This is VERY BAD for the pump and usually means you have a radiator plugged up and it can't supply enough water fast enough for the pump.
High vacuum on the inlet side of the pump will cause REAL PROBLEMS for the pump so don't let it happen,
Have your radiator cleaned out, use a spring in the lower hose, and change hoses about every two years.

----------------------------------------

As for the 'Air' in the system questions,

Any Air in the system is gone the first time the vehile reaches full temprature and the radiator cap 'Burps'.
Doesn't matter if there is a 'Puke Tank' or not, it will vent the air in the system as 'Steam' when it reaches operating temp/pressure listed on the cap.

If you have a 'Puke Tank' hooked up properly, and you have the correct radiator cap for a Puke Tank, the expelled air will blow bubbles in the tank, along with any coolant that gets puked out.

With the proper radiator cap (Two Way Valve) as the radiator/engine cools down, the coolant will be sucked back into the cooling system instead of lost.

Air in the system CAN NOT EXIST at around 15 PSI (operating temp/pressure),
Since outside pressure is around 14.7 at sea level or less, anything above the rating of the cap the system will 'Burp' any air right away.
No air means it can't be an 'Air' differental causing the issue.

It's the 'Voids' in the water that get into the block causing the vacuum at the top hose.
As the voids close up, they draw water back into where they were, and the HYDRAULIC PRESSURE of that water closing the voids is what is collapsing the hose.

Air pressure COULD NOT collapse the hose since there is no AIR PRESSURE in the system.

Again, VOIDS are not AIR, they are not BUBBLES, they are VOIDS where there is a 'Rip' in the coolant.
Coolant is 'Heavier' than water, so it's slower to close the voids, and when it finally does, it will create quite a big of NEGATIVE hydraulic pressure above the coolant pump, and it will do it at the speed of sound when the voids collapse...
It take a while for the pump to catch up, but eventually it will...

Remember, your coolant pump is NOT a pressure pump, creates VERY LITTLE pressure.
It's a VOLUME pump, it's designed to circulate the coolant, not create pressure...

Again, that's a hydraulic thing that people don't get unless they are educated in hydraulic movment and see it themselves...

-----------------------

Does this help explain what's going on?
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Unread 09-18-2011, 10:12 AM   #15
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