lower radiator hose

[89xj]

Does anyone have a list of typical reasons the lower hose would collapse?

I just put a new water pump,all new NPA hoses,CSF radiator,new cap,new T-stat and flushed the system.Now the new hose is collapsing(I have been checking it for leaks and have noticed it sucked until it collapses)Once I pull the rad cap of it pops back open.

This is with all new parts....any ideas?

year? with a radiator cap im assuming 91 or up.

i would also say from the lack of coolant becuase of an air pocket or the wrong water pump. the xj pump is a reverse direction pump. should have an "r" stamped on it somewhere.

 

[sjkimmel99]

I think there's a potential issue with higher levels of suction being created before the thermostat opens. Once the t-stat is open if the hose has the structural integrity to do so it should open up again. Or not. It could be one of those situations where it takes more force to initiate the collapse but only a little force to continue to hold it in the collapsed state. Kind of like the H&K P7 squeeze cocker line of pistols.

Did you notice if the t-stat had any holes drilled around the flat part? Sometimes people add them to allow air out but they may have the effect of also breaking the suction created by the pump before the t-stat opens.

I've read where some people replace as much of the lower hose as possible with copper pipe and just have a short section of hose to connect to the pump and radiator.

however, the air pocket theory sounds good too. With the system full of water how would the pump evacuate enough water from the hose to cause it to collapse. Put another way, in a full system where would the evacuated water go since water doesn't compress.

 

[johnnyc]

I had a problem with both of my hoses collapsing. I discovered that the tube to the overflow bottle was clogged. So when the engine got hot and tried to suck in extra coolant, a vacuum was created, causing the hoses to collapse. (Actually, I don't know if this is a correct analysis, but it works in my brain.)

So anyway, I cleared the tube with compressed air, and it's been fine ever since.

 

[R.Rice]

Man,thanks for all the replies guys.

Here are more of the specifics;Like mentioned above the entire cooling system is new on 1999 4wd xj(ex police model)with a 4.0.

I noticed the hose was collapsed and that it rebound after taking the rad. cap off.I then put the old OEM cap back on to find that it still collapses the hose.

After looking more closely the hose seems to only be doing this after it is cooling down.I drove it home from work today and let it idle in the driveway while looking at the hose.While running the hose was fine.

I am going to go outside in a few minutes and check the over flow hose like Johnny C says.Is there a possibility that the T-stat isn't functioning properly?

I checked the new water pump and compared it to the oem one and the impellers where the same direction.

How cool should I expect this thing to run?After doing all this I found out that my aux fan isn't working due to the motor crapping out.I have a new motor and I am going to install it and wire an on/off switch for it.However,this thing still gets up to about 195-200 with a 180 t-stat(it has been 95deg here the past few days)should I expect this thing to be running cooler than that?

 

[joe_peters]

I would say that the hose collapsing issue was known to the SAE engineers working for Jeep, otherwise the factory hoses would not have come with the springs in them to prevent the collapse.

So, now that the aftermarket (and dealer too?) hoses don't come with the springs, the therory has been put forward that because of improved hose construction the spring is no longer required. My view of mankind is that it is cheaper without the spring, thus no spring.

I advise you find a SS spring of the appropriate size and install it.

 

[5-90]

I had a problem with both of my hoses collapsing. I discovered that the tube to the overflow bottle was clogged. So when the engine got hot and tried to suck in extra coolant, a vacuum was created, causing the hoses to collapse. (Actually, I don't know if this is a correct analysis, but it works in my brain.)

So anyway, I cleared the tube with compressed air, and it's been fine ever since.

Surprise! That's just about spot-on.

Typical reasons for the lower hose to collapse? Just one that I can think of - it's gotten old and soaked with petroleum (usually power steering fluid combined with road oil,) and petroleum is antagonistic to most elastomers. The hose gets soft and weak, and the typical suction provided by the water pump is enough to draw the hose down flat.

Even though the water pump isn't a "positive displacement" type, the flow it generates is still going to create a suction upstream of it - and the first place that offers a potential point of collapse is a weak lower hose.

Good thing engine water pumps aren't of the PD type - you'd probably have to have the support coil moulded into the hose layup, or have a support coil made from flat stock instead of wire stock (such as you'd find in industrial hydraulic suction lines.)

 

[R.Rice]

Update;

I just went outside and the hose was collapsed(it has been sitting for 2 hours)I unplugged the overflow hose and it made a loud sucking sound.The lower hose immediately popped back in shape.

I am going to get a new overflow tank hose tomorrow.The end where it slides onto the radiator looks like it is coming apart on the inside.

Should I expect this thing to run a bit cooler once the new over flow hose is on?

 

[winterbeater]

My 2000 runs at 210 and everything seems fine. That is normal. Get rid of the 180 tstat. It will make your computer run everything rich. Bad gas mileage, fouled plugs, excess wear on cylinder walls, buildup of gas in oil, etc. Your vehicle is engineered around a 195 tstat.

 

[R.Rice]

I was thinking about putting a 195 in it after talking to a few friends who are all mechanics.

I will get a 195 t-stat today when I get the new over flow hose.

 

[R.Rice]

Turns out Johnny C was right.I changed the overflow tank hose and no more collapsed radiator hoses.

Now I have to figure out why this thing isn't running as cool as I hoped it would have.

 

[Ecomike]

thanks guys i appreciate it!

seems easy enough

how about flushing be4 i change the hoses to get the whole system clean?
and then changing hoses be4 putting coolant?

You can do it either way, or do both. Just make sure the other end is open, and do not apply full city water pressure to the system, especially the radiator if you use a garden hose for flushing. Sounds like you have a good idea how to do the chemical plus DI flush already with the old hoses still on it.

My lower radiator hoses are the universal, corrugated hoses that don't need the steel spring, as the hose itself is corrugated.

 

[johnnyc]

Turns out Johnny C was right.I changed the overflow tank hose and no more collapsed radiator hoses.

Now I have to figure out why this thing isn't running as cool as I hoped it would have.

Cool. I'm not right very often. So it's nice to be helpful for once. :thumbup:

 

[Ecomike]

Does anyone have a list of typical reasons the lower hose would collapse?

I just put a new water pump,all new NPA hoses,CSF radiator,new cap,new T-stat and flushed the system.Now the new hose is collapsing(I have been checking it for leaks and have noticed it sucked until it collapses)Once I pull the rad cap of it pops back open.

This is with all new parts....any ideas?

Typical reason is air in the radiator with a closed thermostat, and or a partially blocked radiator that is restricting flow to the water pump, or just air in the radiator, especially with high flow pumps. As already noted a non-functioning return supply that lets air build up in the open system as it cycles hot-cold-hot will result in the air in the radiator version.

 

[Ecomike]

I had a problem with both of my hoses collapsing. I discovered that the tube to the overflow bottle was clogged. So when the engine got hot and tried to suck in extra coolant, a vacuum was created, causing the hoses to collapse. (Actually, I don't know if this is a correct analysis, but it works in my brain.)

So anyway, I cleared the tube with compressed air, and it's been fine ever since.

The engine coolant system only sucks coolant in when the system cools back down and the coolant volume contracts, unless it has an easier path to suck in air instead of coolant. It overheated because it had air where it should have had liquid coolant, thus allowing the hose to collapse. And air does not pump well with a centrifugal water pump.

 

[R.Rice]

Typical reason is air in the radiator with a closed thermostat, and or a partially blocked radiator that is restricting flow to the water pump, or just air in the radiator, especially with high flow pumps. As already noted a non-functioning return supply that lets air build up in the open system as it cycles hot-cold-hot will result in the air in the radiator version.

If that is the case and I now know that the overflow line was blocked(and now has been replaced)should I be looking for something to make sure all the air is out of the system?

 

[Ecomike]

I would say that the hose collapsing issue was known to the SAE engineers working for Jeep, otherwise the factory hoses would not have come with the springs in them to prevent the collapse.

So, now that the aftermarket (and dealer too?) hoses don't come with the springs, the therory has been put forward that because of improved hose construction the spring is no longer required. My view of mankind is that it is cheaper without the spring, thus no spring.

I advise you find a SS spring of the appropriate size and install it.

The only time I can see the need for the spring is on a cold start up just as the thermostat opens and the flow surges, and the internal coolant pressure (versus ambient) is still low. Until the thermostat opens the only flow is through the heater core or renix bottle (the by pass). Once the coolant warms up just a little the internal pressure quickly exceeds the external pressure, especially in the open system which should have no air in it. Pressure build up is much more gradual in the renix since it has air in the coolant bottle all the time, so the renix system may have had more need for the spring. I could see a lower hose collapsing if the thermostat and or radiator are partially blocked, but in that case the spring is not solving the real problem, which is blockage.

Just out of curiosity, how many people here permanently solved an overheating problem by adding a missing a spring? How many developed an overheating problem by leaving the spring out?

All my fluid mechanics and thermodynamics education tells me if that lower hose collapses on a warmed up system, it is due to a low pressure area in that hose, caused by a pump sucking on a clogged radiator or stuck thermostat.