On my 70 SS 396, a short while after I shut the car off the upper radiator hose will start collapsing! What would cause this and how to fix? Any help would be appreciated.
Ken
Ken
collapsing hose
ken70ss396
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On my 70 SS 396, a short while after I shut the car off the upper radiator hose will start collapsing! What would cause this and how to fix? Any help would be appreciated.
Ken
Ken
Collapsing hoses are a sign of trouble somewhere in the system and should not happen under ordinary circumstances.
When the system is cooling, the air inside is cooling and contracting to the extent that it pulls all the coolant toward the vacuum or low pressure center of the air pocket, usually at the top of the tank. In my experience, this is due to a leaky radiator cap that leaks under pressure or you have opened the sytem when hot, and never let the system compleletly cool and return to atmospheric pressure before recapping....a common mistake. Try that first.
If during heating the cap is not holding pressure and vents a bit, then holds pressure going the other way because the pressure under heat is far greater than the vacuum being created, a common occurance I might add, then that will do it too. Fill the system to almost the top, replace the cap with a new one, hopefully a 14 lb or better, and it should not happen again. If it does, believe it or not, you may have a pin hole leak in the top of the radiator in the air space location some where that is so slow that under pressure of heating will exspell air faster than the other way around. I have seen this too and is hard to find. A leak down test usually gives this away overnight.
Springs should be only necessary in some lower hoses in older car applications. This use to be the case where the pump was pulling on an old small tubed radiator and creating negative pressure in the bottom of the system collapsing the lower hose. Usually not a factor with the newer and larger rads of today...esp the big tubed aluminum ones!
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Steve Jack - ConceptOne Pulleys and Brackets / Engineering & Marketing Technologies
When the system is cooling, the air inside is cooling and contracting to the extent that it pulls all the coolant toward the vacuum or low pressure center of the air pocket, usually at the top of the tank. In my experience, this is due to a leaky radiator cap that leaks under pressure or you have opened the sytem when hot, and never let the system compleletly cool and return to atmospheric pressure before recapping....a common mistake. Try that first.
If during heating the cap is not holding pressure and vents a bit, then holds pressure going the other way because the pressure under heat is far greater than the vacuum being created, a common occurance I might add, then that will do it too. Fill the system to almost the top, replace the cap with a new one, hopefully a 14 lb or better, and it should not happen again. If it does, believe it or not, you may have a pin hole leak in the top of the radiator in the air space location some where that is so slow that under pressure of heating will exspell air faster than the other way around. I have seen this too and is hard to find. A leak down test usually gives this away overnight.
Springs should be only necessary in some lower hoses in older car applications. This use to be the case where the pump was pulling on an old small tubed radiator and creating negative pressure in the bottom of the system collapsing the lower hose. Usually not a factor with the newer and larger rads of today...esp the big tubed aluminum ones!
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Steve Jack - ConceptOne Pulleys and Brackets / Engineering & Marketing Technologies
Steve, I bet you are an engineer, your explanation makes me think so and I didn't have any trouble following it, but I would have said to replace the rad cap because the vacuum valve is sticking, but that is just me.
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Leo Paugh
Maryland Chevelle Club #017
A.C.E.S.#3731
progress has little to do with speed, but lots to do with direction.
Maryland Chevelle Club
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Leo Paugh
Maryland Chevelle Club #017
A.C.E.S.#3731
progress has little to do with speed, but lots to do with direction.
Maryland Chevelle Club
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I think the coil or spring is only in the bottom hose,right? Not the top one.I had thought about the rad cap thing but i decided not to post and let the experts handle it.
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Thanks for the info,Yes I did open the cap when it was hot and did not let it cool before closing the cap again. I'll start there, and then replace the cap (16lbs Stant 230) if necessary.Seems a pressure check is in order to see if there is a pinhole leak too. I'll do one step at a time. " The info on this site is worth way more than the price of admisssion!"
Ken
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Ken
My Chevelle
Ken
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Ken
My Chevelle
Chev64, yes indeedy do, an engineering AND technology schools grad of Purdue.
I am sure that the hot opening is the culprit on this. But, take it one step at a time and see what happens. It might be something else.
A good time to bring up a point here on cooling systems and why you should not open them when hot, not to pick on anyone. A lot of people do it. When you open the system when hot you release the friendly pressure in the system that elevates the corrected vapor point of the coolant. This means that if you remove the cap when hot, then replace before cooling the system, it will lose about 25 degrees of boiling protection. The average pressure build up of 10 psi under normal expansion will produce about 239 degrees of boiling protection for just water. So, you can see what happens if the pressure is removed. This also causes the collapsing hose syndrom as mentioned above.
Just some dribble about cooling systems.
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Steve Jack - ConceptOne Pulleys and Brackets / Engineering & Marketing Technologies
I am sure that the hot opening is the culprit on this. But, take it one step at a time and see what happens. It might be something else.
A good time to bring up a point here on cooling systems and why you should not open them when hot, not to pick on anyone. A lot of people do it. When you open the system when hot you release the friendly pressure in the system that elevates the corrected vapor point of the coolant. This means that if you remove the cap when hot, then replace before cooling the system, it will lose about 25 degrees of boiling protection. The average pressure build up of 10 psi under normal expansion will produce about 239 degrees of boiling protection for just water. So, you can see what happens if the pressure is removed. This also causes the collapsing hose syndrom as mentioned above.
Just some dribble about cooling systems.
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Steve Jack - ConceptOne Pulleys and Brackets / Engineering & Marketing Technologies
Thanks for the really great explanations, we sometimes get so involved with trying to solve something with what looks to be the obvious that we overlook the small stuff that will sometimes cure what ails us.
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Leo Paugh
Maryland Chevelle Club #017
A.C.E.S.#3731
progress has little to do with speed, but lots to do with direction.
Maryland Chevelle Club
------------------
Leo Paugh
Maryland Chevelle Club #017
A.C.E.S.#3731
progress has little to do with speed, but lots to do with direction.
Maryland Chevelle Club
Joined
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1,253 Posts
Thanks again for the info! I topped off the system, replaced the cap and then took the car for a ride. No more collapsing hose. I also double checked the hoses to see if I could find any leaks,but found none.
![Image]()
Thanks
Ken
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Ken
My Chevelle
Thanks
Ken
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Ken
My Chevelle
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