Upper radiator hose

[Mjmsc5]

What can cause the upper radiator hose to be pressurized.  When the thermostat opens you cannot even squeeze the hose.  Temperature using an ir gun shows the temp only at 170.  If you take the cap off it obviously depressurizes.  Is this normal?

[spamtank]

What can cause the upper radiator hose to be pressurized.  When the thermostat opens you cannot even squeeze the hose.  Temperature using an ir gun shows the temp only at 170.  If you take the cap off it obviously depressurizes.  Is this normal?

The cap seals the radiator.  It it meant to build up a pressure internal to the cooling system.  This will make the upper (and lower) hose hard to squeeze.  It helps the cooling system function.  Both the air and the coolant in the system expand as they heat up.  Your cap holds that back.  I bet if you check your cap, it may have a pressure rating on it. 

As the coolant expands it may leak past the cap through the overflow hose and into the catch bottle. 

Hope that helps 

[Mjmsc5]

I just figured if it never got above 212, how could it build up pressure.

[spamtank]

I just figured if it never got above 212, how could it build up pressure.

Everything expands a little bit when it heats up.  That's the reason for the overflow tanks on cars now-a-days. 

A quick search on "radiator cap pressure" resulted in a few interesting hits.  Here's a link to look at:

http://www.carsdirect.com/car-repair/understanding-radiator-cap-pressure-ratings

 

[Strawdawg]

The water pump pressurizes it.   The water pump should build quite a bit more pressure before the thermostat in order to further raise the boiling point inside the block.  This prevents localized hot spots from causing the coolant to boil inside the engine.  The radiator cap may be rated at 17 psi which raises the boiling point of straight water  from 212 degs at sea level to 263 degs.

Yet the pressure increase in the block that result from the resistance of the thermostat and radiator tubes can raise the boiling point inside the engine to over 300 degs helping to prevent steam pockets that prevent the heat from being carried away from the block and increasing the likelihood of detonation.

That is one of the potential benefits of an hv pump.

[Mjmsc5]

I understand about the pump developing pressure, but this seems excessive.  The hose itself is visibly expanded and cannot be squeezed at all and the temp is only 160-170.  It is almost as if the radiator is completely clogged.  The radiator is new.

[MEK-Dangerfield]

Just out of curiosity, what is the rating of your radiator cap? It should be something like 13 PSI or 15 PSI. I would think the cap would vent before the hose deformed.   

[Mjmsc5]

It's a new champion rad with a 13# cap I believe.  I let it run today with cap off till thermostat opened and it does flow through the rad.  Put the cap back on and drove around the block.  Hose was nice and hot but not pressurized to the point you could not squeeze down on it.  

[Strawdawg]

...pressure from the pump is pressure..does not matter if the temperature is 170 or not to any great degree.  I would wonder if the hose is soft.

I would also be concerned about a 13# cap being blown open if this is a vertical flow radiator with the cap exposed to high pressure if the hose is not the problem and the pressure is really that high.     If this is a horizontal flow radiator which it sounds like because you say you can see the water circulating, then the cap is on the low pressure side.  If the radiator has small tubes, the radiator might have too much restriction in the case of a vertical unit.   

You might also pressure test the system to see if it holds to make sure a leaky headgasket is not pressurizing the cooling system.  I would think it would be overheating if that is the case when driving the car.

I would vet the hose first, tho

[Strawdawg]

...pressure from the pump is pressure..does not matter if the temperature is 170 or not to any great degree.  I would wonder if the hose is soft.

I would also be concerned about a 13# cap being blown open if this is a vertical flow radiator with the cap exposed to high pressure if the hose is not the problem and the pressure is really that high.     If this is a horizontal flow radiator which it sounds like because you say you can see the water circulating, then the cap is on the low pressure side.  If the radiator has small tubes, the radiator might have too much restriction in the case of a vertical unit.   

You might also pressure test the system to see if it holds to make sure a leaky headgasket is not pressurizing the cooling system.  I would think it would be overheating if that is the case when driving the car, or blowing the cap open.

I would vet the hose first, tho as a 13 psi cap would pop open if the system had unreasonable pressure in it...hose should be hard, but, it should not swell too much unless it is one of the soft ones on its last legs.   Surely the car has a thermostat in it.