I was messing with my car today, as I was doing some tweaking I was under the hood and revving the engine - when I did, I noticed that the lower radiator hose was collapsing and sucking shut. I know that some hoses have the metal spring inside to prevent this, obviously this one doesn't.

Everything in the cooling system - radiator, water pump, hoses, cap, thermostat - is brand new.

Not sure what causes this or what I can do (if anything) to fix, other than find a hose with the metal in it. Thanks.

Fluid dynamics. The solution:

Great, thank you - will find the proper hose.

One more question, though - practically speaking, what issues does this cause? I'm definitely going to fix it, but I'm making my punch list and have about 15 items to deal with, not sure where to slot this. High priority? Or get to when I can? I have no overheating issues, the car never gets above 190 even when pushing it.

Good luck finding an aftermarket hose with the spring in it.

The spring came from the factory only and is present in the hose because the system was vacuum filled on the assembly line, otherwise the spring served no other purpose.

Think about this: The lower hose in on the suction side of the pump, so it should not collapse, because it is pulling water from the radiator.

The only way the lower hose can collapse would be if the return line (upper hose) was not flowing coolant back to the radiator.

The t-stat is closed and coolant is not returning to the radiator, which is normal or you have defective t-stat, clogged radiator, or other restriction on the return side ...

Was the car up to temp and the t-stat open, the upper hose pressurized? or did you just cold start the car and throw some revs at it?

Fluid Dynamics 101

No, the car was fully warmed up. I had driven it for about 20 minutes, pulled up and popped the hood. I thought I heard an exhaust leak, so with my head under there I grabbed the throttle and gave it a little gas (maybe to 2,500 RPM or so). When I did, I happened to look down and saw the hose suck shut. Honestly, I didn't pay much attention to the top hose so I have no idea if it had pressure or not. I'll do some more checking...

if this is a stock car you probably have a 190 degree t-stat...

So the t-stat will cycle open and closed based on the coolant temp, even on a hot day it will still cycle..

After a 20 minute drive you probably warmed the coolant.. but when the fan(s) start cycling.. ..the stock fan switch I believe comes on at 180 off at 170.

Remember coolant had to be 190 or hotter for t-stat to open,
when the t-stat is closed the water pump is not circulating water.

if the car is not "overheating" I would not worry about it. the guys at GM know what they did when they designed the SBC cooling system, so I would not overthink the matter.

All late model cars have 190 or higher t-stats... this help clean up emissions. because it helps engine runs hotter / leaner...

I disagree. Water pumps are of the centrifugal type, and without flow, there is no delta-P across the pump. That is one of the reasons a recirculation path is built into the system.

The reason the hose is collapsing is atmospheric pressure being greater than the inlet pressure on the pump above which the pliable rubber hose can withstand. Being warm means the stiffness of the hose is reduced. And, of course, this is why the factory uses an internal spring to resist this collapsing. It isn't limited to 3rd gens, it's been used for decades before that.

If you can't find a hose with a spring, or a spring, one solution would be to get a flexible hose with the correct end diameters and approximate length. They have the spring molded into them.

http://www.martiauto.com/faqfocus.cfm?qid=20


I prefer to read and understand.


Atmospheric pressure is only valid when the engine is cold. (t-stat not open) when the t-stat is closed the water pump
re-circulates the coolant thru the engine block/heads and will do this until the coolant temp reaches the opening temp of the t-stat... 190 degrees for a stock 3rd gen. (your delta-p non-sence)

as stated in the article: "The events that lead to the thought that "I need a spring" are based on either an insufficiently warmed up engine or a clogged radiator.

The spring does not take care of these events. It merely masks a symptom. If, after your vehicle has reached normal operating temperature but you experience a collapsing hose, have your radiator tested."


But go on and look for that elusive spring. I am sure someone is selling them to the un-informed.

Fronzizzle, make sure that the cooling system is full. No air what-so-ever. Also check the water level in the overflow bottle when cold, then that it is higher when the engine is hot.

The older systems did use the spring in the lower hose as there was air in the system. The radiators were never fully filled.

RBob.

www.cjponyparts.com

Stainless lower hose springs.
Ask them if 1 will fit your application. A guy on another forum said it would, but if you want 1 verify it would fit. IIRC like $7.00

You have the wrong type of radiator cap

If yours calls for vented/non vented make sure it has it and is the correct poundage. Been there done that. You wont need a spring

dynamikz

I wondered about the cap as well. I'm not sure what the correct cap is - do I just look one up for a stock 1985 IROC? The waterpump on my car is stock, but I have a 180 T-stat and 3-core aftermarket radiator that came with a cap.

Replacement hoses did come with the spring just like the factory hose, but over time manufacturers deleted the spring altogether. My guess is as demand for these hoses dropped, so did adding the spring in order to keep costs low.

My one question is have you tried removing the cap when cold and starting the engine? Doing this and letting the engine come up to temp will bleed the trapped air in the system. I do this any time I've changed hoses and/or changed cooling fluid. The radiator will "burb" when the thermostat opens and spill out fluid from the filler neck. Simply top off at that point and put the cap back on. The cap should be rated for the stock pressure which should be 16 pounds. This should take care of the hose collapsing entirely, although you'll still see some hose collapse when kicking the throttle to high revs.