Radiator Hose is flat????

[kenny811]

So after a day of wheeling yesterday I noticed that my bottom radiator hose was flat. While the motor was at an idle( I was airing up ) the lower hose was sucked flat. This is my 4th jeep and I have never seen or heard of this. I noticed this a few weeks ago but just thought it was pressure or hot / cold. But it did it again. Any ideas???

 

[the_weirdo]

There is usually a spring inside the lower hose to keep this from happening. The water pump is sucking water through and collapsing the hose.

 

[kenny811]

All the hoses I looked at didn't have the spring. But why would the water pump have so much suction?

 

[old_man]

The problem isn't the amount of suction, but rather the restriction in the radiator.

 

[kenny811]

The problem isn't the amount of suction, but rather the restriction in the radiator.

So are saying that it might be a blocked or clogged radiator?

 

[Lowrange2]

There's a restriction somewhere, yes. Flush the whole system. If it's bad enough to collapse the hose I'd suggest a new radiator.

 

[NotMatt]

The factory Mopar lower radiator hose (about 30 bucks from the dealer) has the proper metal spring coiled inside to prevent this. Every aftermarket parts store hose I've ever looked at does NOT have it.

Er-go... I buy the factory mopar one whenever I have to replace a lower hose. I've seen the lower hose suck flat with brand new radiators and a flushed system that has no restrictions. I don't know why the lower hoses suck flat, but obviously chrysler decided it was a good idea to put that spring in... so I'll only use hoses with it.

 

[Lowrange2]

The factory Mopar lower radiator hose (about 30 bucks from the dealer) has the proper metal spring coiled inside to prevent this. Every aftermarket parts store hose I've ever looked at does NOT have it.

Er-go... I buy the factory mopar one whenever I have to replace a lower hose. I've seen the lower hose suck flat with brand new radiators and a flushed system that has no restrictions. I don't know why the lower hoses suck flat, but obviously chrysler decided it was a good idea to put that spring in... so I'll only use hoses with it.

Yet, I've used a hose without the 'spring' for as long as I've had the Jeep and never had an issue.

 

[Ian Christiansen]

Did you recently upgrade to a high flow water pump?

 

[jeeperjohn]

If the vent on your radiator cap is not working it could create a suction in the system but it would be sucked down before you started the engine. If the hose is sucked down at idle it would starve the engine for coolant at anything above idle.

 

[kenny811]

Wow some great posts on this, I have been around allot of jeeps, and have never seen or heard of this. Found one guy that used the spring in the hose and the spring got sucked into the water pump. Mine is not a high flow water pump and even though its in the 30's & 40's here in the pacific north west the engine temp doesn't go above 185 / 190. No where near 210 so it makes me think its not a flow issue. Tonight I will flush the system and make sure there is no block. The hose with the spring might be a good fix for a flat hose, but something is causing the hose to suck flat, I would rather know why and then pick the right hose, then just put a deal OEM hose on it.

 

[kenny811]

If the vent on your radiator cap is not working it could create a suction in the system but it would be sucked down before you started the engine. If the hose is sucked down at idle it would starve the engine for coolant at anything above idle.

Last night with the engine cold, hose sucked flat, I popped the cap and got a release of pressure and the hose went back to almost round. I have new caps on the shelf I will try a new one.

Thanks John

 

[Outlander560]

the reason it sucked flat is because you put an open in the system allowing it to suck air in..the caps not at fault. the system runs at about 14psi most coolant systems do...when you took the cap off you took away the systems ability to create pressure so the hose rounded off..like previously mentioned get a new lower hose with a spring inside of it. the hose itself is thin to begin with so obviously it will collapse which is not good..

you flushed it which was good especially if you have not done it for quite sometime...before you start throwing new radiators or caps into the equation replace the hose with the correct one.

 

[NotMatt]

the reason it sucked flat is because you put an open in the system allowing it to suck air in..the caps not at fault. the system runs at about 14psi most coolant systems do...when you took the cap off you took away the systems ability to create pressure so the hose rounded off..like previously mentioned get a new lower hose with a spring inside of it. the hose itself is thin to begin with so obviously it will collapse which is not good..

you flushed it which was good especially if you have not done it for quite sometime...before you start throwing new radiators or caps into the equation replace the hose with the correct one.

IMO, this is one of those cases where whatever the parts store hands you is not necessarily the right part. I can think of another similar problem with Dorman harmonic balancers not fitting, flexplates that don't have the holes in the right place, etc.

Somewhere, some engineer designing replacement parts at some manufacturer decided that "silly" spring wasn't needed and they could save a few pennies by doing away with it... they made a billion lower radiator hoses without it, and they sell them to all the companies like Gates, Napa, Duralast, etc that brand it with their name and resell it... and then you end up with not being able to ever find the correct part in a parts store.

To the OP: Go to the dealer, get the right part. Sometimes that's the answer even though I hate to say it.

 

[frijolee]

Something doesn't add up. Radiator cap pressure values are given in gauge pressure (not absolute). Positive gauge pressure is by definition above ambient. If your hose is collapsing you're well below ambient pressure which means the water pump is trying to draw fluid but there's enough restriction upstream to create a significant pressure drop. It should be more likely to happen with the engine cold because the pressure drop is relative to ambient instead of positive pressure in a hot system. If it does it while hot either your cap isn't holding pressure or you have more than 14 psi pressure drop to get below ambient.

Even without a spring it should take quite a bit of pressure drop to collapse a hose. That pressure drop has to come from restriction somewhere. How's the top hose feel? If it's tight then we have a pretty clear radiator restriction. If there's no pressure or if it collapses easily under finger pressure that says the draw from the water pump is not affected much by the radiator and the restriction is upstream.

+1 for a fluid flush (IE, pull the thermostat and stuff a hose in the block, then do the radiator too)

The Jeep spring hose may help but there's more going on here as standard internal fiber hoses work fine in 99.99% of applications. I'd want to figure it out the root cause before putting a band-aid fix in place to fix a symptom.

 

[kenny811]

If it turns out to be the hose, and it indeed needs a spring I will be the first to admit it. But like NotMatt said they make a million of these hoses with out springs, I cant be the only one that has "flat hose" So I will first flush the system, if that doesn't do it I have a brand new radiator from my 89 ( its an open system ) I will try that. Im sure the spring house is a great product but no hose should suck flat for any reason unless there is a problem. Im going with a block or a clog in the radiator. But I will post up as soon as I do it and let you know the findings. Stay tuned!! And you would think that as may xj's & mj's out there someone else would have had this happen at some point.

 

[NotMatt]

If it turns out to be the hose, and it indeed needs a spring I will be the first to admit it. But like NotMatt said they make a million of these hoses with out springs, I cant be the only one that has "flat hose" So I will first flush the system, if that doesn't do it I have a brand new radiator from my 89 ( its an open system ) I will try that. Im sure the spring house is a great product but no hose should suck flat for any reason unless there is a problem. Im going with a block or a clog in the radiator. But I will post up as soon as I do it and let you know the findings. Stay tuned!! And you would think that as may xj's & mj's out there someone else would have had this happen at some point.

Let us know what you find out.

I've seen it happen on at least three other rigs with hoses that don't have the spring. However, none of these other rigs seemed to show any cooling problems from what I could tell... just the squished hose. Whether that means the hose wasn't completely flat and did let some coolant through, or it opened back up at something other than idle, I'm not sure. Every time I saw it, (two of my rigs, and one of a friends) the lower hose was replaced right away with a dealer one with spring and the problem went away obviously.

Which makes me think it may be more common than we think, but since the hose is buried down underneath the power steering pump and factory electric fan, and the "flat" hose may not completely restrict the coolant, maybe it just doesn't get noticed.

 

[G2WANIT]

Something doesn't add up. Radiator cap pressure values are given in gauge pressure (not absolute). Positive gauge pressure is by definition above ambient. If your hose is collapsing you're well below ambient pressure which means the water pump is trying to draw fluid but there's enough restriction upstream to create a significant pressure drop. It should be more likely to happen with the engine cold because the pressure drop is relative to ambient instead of positive pressure in a hot system. If it does it while hot either your cap isn't holding pressure or you have more than 14 psi pressure drop to get below ambient.

Even without a spring it should take quite a bit of pressure drop to collapse a hose. That pressure drop has to come from restriction somewhere. How's the top hose feel? If it's tight then we have a pretty clear radiator restriction. If there's no pressure or if it collapses easily under finger pressure that says the draw from the water pump is not affected much by the radiator and the restriction is upstream.

+1 for a fluid flush (IE, pull the thermostat and stuff a hose in the block, then do the radiator too)

The Jeep spring hose may help but there's more going on here as standard internal fiber hoses work fine in 99.99% of applications. I'd want to figure it out the root cause before putting a band-aid fix in place to fix a symptom.

I don't think you're taking into account the fact that the hose will get more playable the hotter it gets, and from my experience this is accentuated with age. If this hose is old it will fold like a wet taco under pressure.

My 1992 VW GTI called for a lower hose with a spring in it as well, its obviously something they use in certain applications where the manufacture knows it is needed. If the parts store is selling you a hose without the spring they are peddling an inferior product to you or a product that is not application specific.

 

[frijolee]

I agree that they can get softer with age but your logic about heat doesn't work because if it's hot it should be under pressure internally so where did that pressure gradient come from to have it collapse at all in the first place? That only happens with a restriction in the line. I hardly think the absence of a spring is singularly related to an inferior product. You could just as easily argue that only an inferior product would need the spring. Fwiw I've never seen a silicone hose that had one.

 

[kenny811]

Ok here is what I found and the results. I flushed the block & radiator, ran the jeep for a day. When I checked the hose the next day there was so much pressure on the hose im surprised it didn't blow up. The pressure didnt relese at the cap because the overflow tube was clogged at the cap, and in 3 other spots between the radiator and the overflow bottle. I fixed it and the lower hose as been fine for 3 days. I check it as often as I can and its fine. So again im not saying it was the overflow tub, but it seems that way. I will keep checking it.