Radiator hose flattens when revving engine. - Hot Rod Forum : Hotrodders Bulletin Board
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Old 03-21-2008, 05:16 PM
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Radiator hose flattens when revving engine.

Just installed 406 in my Cutlass, got it started and let it run for a min to allow time to heat up. I noticed only when I raised the engine both the top/bottom radiator, and heater hoses would swell then flatten out. I have swapped thermostats and tried 2 different radiators, but still having the same problem...

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Old 03-21-2008, 06:01 PM
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You have good flow, that's for sure! LOL

When that happens (normal but not usually seen), you could have really soft hoses OR need hoses with the springs inside to keep them in form.
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Old 03-21-2008, 06:31 PM
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Originally Posted by Jmark
You have good flow, that's for sure! LOL

When that happens (normal but not usually seen), you could have really soft hoses OR need hoses with the springs inside to keep them in form.
I was thinking maybe it wasn't getting enough flow hence the flattening of the hoses. You said something about hoses w/springs in them I've not seen such a thing, unless your talking about the metal/aluminum hoses that a lot of people use to dress up their engine.
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Old 03-21-2008, 07:02 PM
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The make molded hoses that are made for exact model of engines and some flexible hoses that have a wire wound in a spring like shape that are inside the rubber hose. They keep the hose in shape.
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Old 03-21-2008, 07:16 PM
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Quote:
Originally Posted by DeathRattle
The make molded hoses that are made for exact model of engines and some flexible hoses that have a wire wound in a spring like shape that are inside the rubber hose. They keep the hose in shape.
Well I'm definitely going to check into that because right now this is the only thing holding me back from driving the car. I saw the flattening of the hoses and freaked.

Now another question: What would be the symptoms of having too small a radiator?
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Old 03-21-2008, 07:48 PM
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Quote:
Originally Posted by Olds86
Just installed 406 in my Cutlass, got it started and let it run for a min to allow time to heat up. I noticed only when I raised the engine both the top/bottom radiator, and heater hoses would swell then flatten out. I have swapped thermostats and tried 2 different radiators, but still having the same problem...
You're seeing RPM induced pressure surges created by the pump. I wouldn't call it a problem unless you've got an overheating issue you can't chase down. What you're seeing this is normal, however, you don't want the lower radiator hose to the pump to collapse. This is the pump intake and is under suction, if it closes off that will starve the pump for coolant.

The return hose at the top front of the engine to the radiator is normally under pressure and will expand somewhat as revs, thus hydraulic pressure in the engine rises above hydraulic pressure in the radiator. If the throttle is suddenly closed from fairly high RPM you might see this hose and the heater hoses expand and contract some as hydraulic pressure surges form in the engine.

I use the term "hydraulic pressure" to denote a difference between pressures induced into the coolant by the actions of the pump against the restrictions of the engine's cooling passages and the regulation of the thermostat. This is different from what one normally thinks of radiator or coolant pressure which is caused by the combined effects of heat expanded coolant and its vapor pressure which are what the pressure cap is managing.

Bogie
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Old 03-21-2008, 10:28 PM
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If you have a spring in the hose it goes on the bottom hose, the top hose does not need one. Try burping the cooling system, run it with the cap off for 10 minutes, let the thermostat open all the way and the coolant circulate for a while and get all the air out. When the thermostat first opens up with the cap off the radiator will push about a quart of coolant out onto the ground, then the level in the radiator will go wayyyyy down. Top it off and repeat one time and it should be free of air.
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Old 03-22-2008, 04:16 AM
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Quote:
Originally Posted by oldbogie
You're seeing RPM induced pressure surges created by the pump. I wouldn't call it a problem unless you've got an overheating issue you can't chase down. What you're seeing this is normal, however, you don't want the lower radiator hose to the pump to collapse. This is the pump intake and is under suction, if it closes off that will starve the pump for coolant.

The return hose at the top front of the engine to the radiator is normally under pressure and will expand somewhat as revs, thus hydraulic pressure in the engine rises above hydraulic pressure in the radiator. If the throttle is suddenly closed from fairly high RPM you might see this hose and the heater hoses expand and contract some as hydraulic pressure surges form in the engine.

I use the term "hydraulic pressure" to denote a difference between pressures induced into the coolant by the actions of the pump against the restrictions of the engine's cooling passages and the regulation of the thermostat. This is different from what one normally thinks of radiator or coolant pressure which is caused by the combined effects of heat expanded coolant and its vapor pressure which are what the pressure cap is managing.

Bogie
So what your saying is, this is all normal, and nothing to concern myself w/unless the car starts over-heating??? This will definitely be something I will continue to monitor. Just a scary sight to see ya know, because the hose was flattening as if it wasn't getting enough coolant, as if too little water was passing through it...Thanks all for the responses they are greatly appreciated!
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Old 03-22-2008, 10:53 AM
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I'd also try a new radiator cap, I've never seen all the hoses get sucked closed but if the top one is going flat it's usually the cap.
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Old 03-22-2008, 11:25 AM
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Quote:
Originally Posted by gregb
I'd also try a new radiator cap, I've never seen all the hoses get sucked closed but if the top one is going flat it's usually the cap.
I'm going to pick-up a new radiator cap today sometime...
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