Hot Rods Lower Radiator Hose collapsing

Hi All:
Running a 350 Chevy crate motor in my street rod with a Walker radiator and Yogi overflow tank. After attending the last Good Guys in Pleasanton I popped the hood and noticed the lower radiator hose was collapsed. Car was not overheating (180-degrees) or boiling over. As soon as I loosened the radiator cap the vacuum was broken and the hose returned to normal. Any ideas what is causing the hose to collapse in on itself? Radiator cap? Bad thermostat? I could put a spring in the lower hose to keep it from collapsing, but that's not fixing what the real problem is. Any ideas out there??

 

Because of the suction from the water pump, and the heat, lower hoses DO want to collapse. The cure IS a spring in the hose. This used to be standard practice, but manufacturers found yet another way to get cheap, and removed the spring. Works in a lot of cases. Not yours. Add a spring, stop stressing.

Cosmo

 

Actually, the missing wire spring in the lower hose *is* the problem. Your water pump is pulling the water through it and- in doing so- collapsing the lower hose.
If you use a lower hose that includes a spring inside it, you'll solve the problem.

 

I believe the water pump may be collapsing the lower hose,,it needs a reinforcing spring.

BTW,that's a nice looking deuce. HRP

 

Looks like Cosmo types faster than me.

 

also try to find a cap that allows the vacuum to pull the water out of the overflow tank too not all caps have this function . as when it cools the vacuum is supposed to pull the makeup water out of the overflow tank if the portion of the cap is not working the hose will collapse also as it cools .

 

I've never really understood how a system with 15 psi in it can collapse a hose, but it does.
I've not given it much thought because the spring is the way to keep the hose from collapsing

 

mostly from the restriction of the radiator core passages and external air pressure on the hose surface and the suction of the pump impeller , if it gets bad enough the impeller gets pits on it from cavatation implosions .

 

The pressure isn't the same throughout the system, when it's at operating temp and above.

 

Just went through this with a Mopar guy that was having heating probs at speed. His pump was actually putting enough suction on the bottom hose to collapse it. He had problems finding one to fit his application with a spring in it, so eventually had to buy another hose the same diameter just to rob the spring out of it. I've searched online and found springs for early Mustang hoses, and I know they are available for suction lines for sprayers, but some of the odd sizes are not easy to find. If someone is looking for a marketing opportunity start making springs out of stainless steel for cheapy rad hoses. If you end up making your own, or cutting one down, make sure you kink the end of it in, away from the hose. If you don't, it will eventually eat it's way out of the hose from vibration and give birth like an alien.

 

What Cosmo said.
Lower Hoses DID HAVE the spring inside the hose, some manufacturers have eliminated them.
KKEYSER, the missing spring is the problem, installing the spring IS the fix.

 

The answer is always ''put a spring in it'' but where the hell do you find a spring? I'm always looking for shit like this at the junk yard with no luck. Dave

 

Gates hoses and Goodyear used to have it in the back of the books . have to go to a quality parts store to get them . Napa used to carry them , but the way they are going ..

 

You may have to buy another bottom rad hose with a spring and remove the spring and put into the bottom hose you have now, if you can't find one?


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Had this happen and my helper didn't realize the spring would still work even rusted in 2 pieces and removed it, thank god for duct tape because it stiffened it enough to finish the weekend!

 

ummm..... I don`t get it, but maybe I`m missing something... you guys build the most awesome guys on the planet, but have trouble finding a radiator hose spring....? Just get some 3-4 mm weldingwire (use stainless if that makes you feel better ),wrap it around a correct diametre pipe, bent the ends inward and stuff it into the hose...

 

We certainly don't build "awesome guys".

 

Head down to the parts store and get a radiator hose of this style, there is zero chance it will ever be sucked closed.

 

oops...LOL cars that is.... ;-))

 

Probably should have added - Advance Auto Parts sell the springs, in three sizes, so that you can get the correct one.

Cosmo

 

I did this on my blower motor and it's still holding good, 3 years on..

 

When you see a hose collapsing, the radiator must be a restriction I guess.

+ 15 psi ( roughly 2x atmospheric) on the top tank and less than 0 on the bottom tank.

 

Not zero. The atmosphere is crushing the hose with 14.7 psi. (at sea level.) It just has to be slightly less than atmospheric inside the hose, to squeeze the rubber.

(pressure in the tank is 15 psi on a gauge, but ~30 psi absolute.)

 

Just think about how pliable that hose becomes when it gets hot, and 15lbs is just what the cap holds back under positive pressure, not under negative pressure, where there is no limit at all. It could be a lot more than 15 lbs, but even if it isn't, I think 15lbs of suction could easily distort a hose under temp.

 

Change the radiator cap


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It takes very little pressure difference from inside to outside to collapse the hose.

Lay the hose (without spring) on the table & lay a 2lb hammer on it. The hose starts to go flat.

Put it in the car & wind 'er up. If cold, there's just 14.7 psi in the top tank (and everywhere else at sea level), but you're pulling so much water through at high RPM the radiator blocks just a little flow & now there's only maybe 13 psi in the bottom tank at high flow rates.

There's still 14.7 psi on the outside too, so the hose starts to go flat. chop the throttle & it swells again.

If the radiator's somewhat plugged this could happen all the more readily.

 

Good advice if the system's not building pressure.

(Does anyone use a "pump" type cap tester anymore? I used to have one with an adapter--you tested the system pressure, or could use the adapter to test the cap too.)

 

You guys would make a wet dream complicated....

Argue with a fence post ....

And Not explain or accomplish a damn thing.


An open radiator has a pressure reading of ZERO in open atmosphere.

You know it all guys understand IF / then statements ?


IF the bottom hose collapses,
Then the open atmospheric pressure is greater than the internal hose pressure.

With the top tank at 15 psi -
if bottom tank is not at 15 psi
Then the core is a restriction between the top tank and the bottom tank.

 

Well, I wan't arguing with you. I just thought this was confusing:

"+ 15 psi ( roughly 2x atmospheric) on the top tank and less than 0 on the bottom tank."

...and yes the core is a restriction. It's a big restriction at high RPM.

<Edit> OK, sorry, I was disputing the "less than O" thing, but just because of how it's phrased. Less than O sounds like a vacuum is being drawn. There's no vacuum in the lower hose. It just collapses if it's less than atmospheric pressure inside the hose.

You clearly understand the principle of it all. Your last post explained it quite well too.

 

Last time I checked, anything less than atmospheric will draw vacuum in inches.
Yes less than zero psi is a vacuum.

Earlier you stated that if you had 13 psi in the lower hose it would collapse.
Uuuuuhh? What?

You need some pretty damn sophisticated equipment to measure pressure that includes atmospheric pressure also, so unless you have one in your tool box lets keep this on a normal level. And 14.71 might as well be 15 for discussion sake. Open atmosphere reads Zero psi on most gear head gauges.

If you read 13 psi in the hose you have 13 psi inside the hose and zero outside. The hose is not going to collapse. You have zero psi inside the hose and zero outside the hose will not collapse. Once you have less than zero inside the hose the hose will collapse.

So now get your scientific calculator out-
Tell me how the hose collapses with 13psi in it?

If any of this is unclear, refer to the first 3 lines of post #28