I drive my car 2-3 days a week. Lately, I notice before I start the car in the morning, the upper hose is usually collapsed (vacuum). So i usually open the radiator cap to let air in so the hose returns to normal.

My initial thought was that it could be caused by cold temperature. It's like putting a closed warm bottle of water in the fridge. The bottle of water will contract after it's cold. But now i'm worried that it's a problem with the cooling system.

Does anybody else ever notice that ? I'm check tonight to make sure the recovery tank hoses are not clogged. Hmmmmm

thanks

 

When the car is cold it should be running in a closed loop until it comes to operating temperature and the thermostat opens up. Not sure if this is the reason, but tomorrow, go out out 10 minutes b4, start your car and let it warm up. Check the hose before and after it is at temp!

 

Are you low on coolant?
It also sounds like that hose may need replaced.

 

I would have thought that any loss of pressure in the system would result in coolant being drawn from the overflow bottle to replace the void. Could that be blocked?

 

I just read from another forum that someone with an FX was having same problem. It turned out the center piece of radiator cap was stuck...

I think it might be my case as well. I see overflow tank is nearly at FULL mark at startup, as if coolant is not drawn back to radiator overnight.

First of all - can someone explain to me how overflow tank works ? When the pressure in radiator exceeds certain pressure, it pushes up the spring of the radiator cap, allowing coolant to go to the overflow tank. As engine is cooling (pressure goes down), wouldn't the radiator cap block the overflow tank opening ?? How is coolant drawn back to the radiator ?

 

Dunno but I read recently in a discussion that if your hose has collapsed it means you have a faulty rad cap. I think it was a discussion about lack of heat inside the cabin.

 

There shouldn't be any air within the radiator or hoses. If there is than the overflow function will not work. Top off the radiator with antifreeze when the engine is cool. You might have to bleed the system of air but you can first try topping it off and hoping that the air works itself out.

Basically, when your cooling system (radiator and hoses, etc.) is correctly full of antifreeze, the overflow tank holds the excess antifreeze that is displaced out of the cooling system due to heat expansion. When the system cools down and the antifreeze contracts, the radiator will siphon back antifreeze from the overflow bottle, keeping the radiator full of antifreeze.

I think in your case, you are low on antifreeze (you should find out why) in the radiator and therefore the system is unable to siphon antifreeze from the overflow and is instead creating a vaccuum when cooling, thereby collapsing the upper radiator hose. It's possible that the overflow hose is clogged, because if it's not than im not sure there would be enough "vaccuum" to collapse the upper hose.

 

well its a good time to upgrade them to the silicone hoses and to flush out the radiator system

 

the radiator cap keeps the system pressurized to 14-16 PSI this allows the coolant not boil over as it raises the temp at which the fluid will boil

 

The coolant level in the overflow tank was way way ABOVE the MAX line after the engine was cool enough that I could open the radiator cap by hand. There was some residue at the bottom of the overflow tank. I took it out and cleaned it well. I don't think that's enough "dirt" to clog the hose. The radiator cap appeared to be in good condition, but i cleaned it anyway. I topped off the radiator with only a tiny bit of coolant. The radiator was almost full.... And I do not see any evidence of coolant leakage on the garage floor.

Temp gauge has been stable and normal. So it doesn't give me a good indication of air in the system. I just hope that it's nothing serious like blown head gasket or failing water pump or heater core problem...

 

mfung, I have the same problem that you are describing. There is no sign of coolant leak. The coolant level in the overflow tank is always sufficient.

Should I worry? Is this something that will be cover under the warranty?

 

I'd say that your rad cap is malfuctioning. It happens.
Try a new one.

C.

 

+1^^^^ absolutely, I agree with Colin, it certainly sounds like a bad radiator cap. Replace it.

 

+1^^ Check out the TSB site. I recall that there was an issue with some of the radiator caps and the dealers were changing them out.

 

thx, let me check the tsb and w/ the dealer.