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Upper Radiator Hose Collapsing When I Rev Engine??

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Big6ft6

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Location
Madison, WI
1991 350 TBI

What would cause the upper radiator hose to collapse when I rev the engine?

Cooling system seems to be working fine, we've had some hot days and no problems.

just seems wierd.
 
Bad hose. Replace it.

Some new ones even come with a wire insert that helps hold it open.

May as well replace the lower one while you're at it. Last time I did one, then the other started collapsing as well, so I had to drain everything all over again! :doah:
 
Bad hose was my first thought..(And I think is old) but then I got thinking, why is it creating such a negative pressure in the upper hose when there are other pathways from the waterpump?

Maybe I'm over-thinking it. I'll replace the hoses and check the thermostat, I also have a new radiator sittin' in the garage from when I thought I had a radiator leak, might as well put that in too.
 
I have seen the upper hose completely collapse. It was causing an overheating issue.

Make sure the new hose has wire in it to prevent this
 
Just went through this with my mothers '94 pick up, she even went to a shop and they charged her over $200 to flush out the system, still did it, and they didn't even clean off the radiator cap of the sludge that seems to be a typical thing in the 4.3 v-6's.

Anyways, it's a breathing system of sorts I found out, while under load, it tries to pull extra coolant from the overflow tank, when the excess coolant isn't needed, it pushes it back. In her case, the little hose going to the overflow tank was clogged with this muddy sludge type stuff, not letting it pull any extra coolant, basically creating a vacuum, so the only thing it could do, was pull the upper hose shut.

Her and my dad cleaned out that hose and tank of the crud and it's been working fine ever since.
 
and I have yet to see a new hose to be sold with this coil wire inside it like the lower ones have
 
likewise, haven't seen a wire in 10-15 years. Gates or Goodyear have good hoses. Or does Goodyear make gates, or gaterback, dunno, can't remember.
 
4xcrazy said:
Just went through this with my mothers '94 pick up, she even went to a shop and they charged her over $200 to flush out the system, still did it, and they didn't even clean off the radiator cap of the sludge that seems to be a typical thing in the 4.3 v-6's.

Anyways, it's a breathing system of sorts I found out, while under load, it tries to pull extra coolant from the overflow tank, when the excess coolant isn't needed, it pushes it back. In her case, the little hose going to the overflow tank was clogged with this muddy sludge type stuff, not letting it pull any extra coolant, basically creating a vacuum, so the only thing it could do, was pull the upper hose shut.

Her and my dad cleaned out that hose and tank of the crud and it's been working fine ever since.
Click to expand...

Ding ding ding!

Just learned about this today.
Couldn't have said it better myself.

The muddy sludge is actually rust. :doah:

Another thought, is a jammed t-stat can also cause this.
As the pressure is attempting to pull fluid, with the t-stat jamming up the passageway.

Thusly, causing a 'sucked in' pressure hose.

But you would have an obvious 'running hot', issue.
 
Also, a bad vaccuum hole, in yer radiator cap, will cause excess pressure in the system.
It's job is to let air into to the system, and out of it, to regulate coolant system pressure.

Bam!
 
Older vehicles usually had a spring inside the lower hose,to prevent it from collapsing under high speed driving conditions....but not every engine has or needs one ....................................................................................................I'm not sure if since newer GM's use a reverse rotation water pump with the serpentine belts,if that would make the upper hose the "suction" side of the system,instead of the lower,as on the older vehicles--if thats the case,it wouldn't hurt anything to add a spring to the upper hose,if you can find a suitable one...I learned to save things like that instead of tossing them in the rubbish with the old hoses--sometimes things like that are "impossible" to find separately and aren't cheap if you can!..
 
Water still flows the same, just the different pump design, yes the pump spins reverse, but the vanes inside still direct the water in the same direction as the old setups.
 
4xcrazy said:
Anyways, it's a breathing system of sorts I found out, while under load, it tries to pull extra coolant from the overflow tank, when the excess coolant isn't needed, it pushes it back. In her case, the little hose going to the overflow tank was clogged with this muddy sludge type stuff, not letting it pull any extra coolant, basically creating a vacuum, so the only thing it could do, was pull the upper hose shut.
Click to expand...


Spot on. Overflow system works all the time. A hot engine will 'push' a little coolant into the overflow and a cold one will draw it back in. When you rev up a cold (or malfunctioning) system, the higher coolant pressure between the water pump and the thermostat creates a lower pressure on the suction side (thermostat to pump inlet) which is supposed to draw fluid from the overflow until the system is full. Water is not compressible, but air is. The collapsing hose is a sign of too much air in the system.

Also, rotation makes no difference. All radiator inlets are at the top and outlets at the bottom b/c hot water naturally wants to rise and cold falls and the column of water in the radiator helps the NPSH of the water pump and keeps it from cavitating. Also there's usually a small amount of air at the top.
 
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