This can be due to one of a few different things...First of all, water flows from the engine to the bottom of the radiator, using the water pump and gravity, and the water returns from the radiator back into the engine on the top side.
Thermostat isn't opening...this causes the water / antifreeze to remain in the engine, and not flow through to the radiator. If the water / antifreeze gets hot enough, it should activate the thermostat and water should flow into the radiator through the bottom radiator hose.
The bottom radiator hose is either worn out (there is a spring inside the length of the bottom hose. it is there to keep the hose from collapsing under the suction pressure during normal use) If the hose feels spongy, soft, or shows signs of cracking, replace it.
The radiator may be clogged, preventing the water from flowing freely through all of the 'fins' in the grill section of the radiator. Hot water usually isn't just in the top section during a clogged radiator situation...
SOURCE: 1990 toyota corolla wagon 1.6 liter 5 spd. overheating
you've got a possible blockage in the head or block.
SOURCE: 2002 dodge 1500 Changed radiator, thermostat, and hoses. No heat
Why was radiator replaced?Did it have heat before ? If it was plugged, the heater core may also be plugged. Try flushing it with a water hose in both directions. I dont know why the botton radiator hose would be cold, the radiator should be a uniform temp and the air coming through the radiator should be HOT, when the engine is at operating temp. What condition was the old coolant? if it was rusty, the water pump may have lower flow than normal.
SOURCE: 1991 honda accord is overheating. Installed new
When the car is completely cool,check the electric fan(s) for smooth rotation.
Clean/check/change the thermo sensor,contact and wire.
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Excavate air pocket in coolant system / check for head gasket leak
This test will kill two birds with one stone.
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MAKE SURE THE COOLANT SYSTEM and ENGINE IS COLD!
RAN THIS TEST IN A WELL VENTILATED AREA ONLY!
You will spill some coolant during this air pocket purge test.......BE
KIND TO THE ENVIRONMENT and ANIMAL please clean up after the test!
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Put the front end on a pair of ramp or park your car on a VERY STEEP HILL (radiator facing top of the hill) .
Top of the coolant reserve tank
Let it ran for 10-15 minutes.
Monitor for air pockets escaping from coolant reserve tank.
Small amount of bubbles is OK at 1-5 minute mark
After the thermostat open up (after 195 F warm up) at
5-12 minute mark or after high idle you should see less bubbles.
If you do not see any in rush of bubbles then your thermostat may be
partially stuck or rusted badly inside the thermostat hosing.
Give the thermostat host few gentle taps.
If you see larger bubbles surfacing after 15 minutes then should do a
hydrocarbon (HC) dye test to test for potential head gasket leak.
Let engine cold down and top off coolant reserve tank.
Start monitor for coolant lost
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A coolant flush is require every 2 years or 24,000 miles.
I recommend the thermostat that has a relief pop-let to reduce the change of burst radiator and coolant hoses.
Make sure you get a new thermostat gasket,black RTV and fresh coolant for the job.
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SOURCE: 1991 daihatsu applause super selection eng-HD-E1
let the car get up to operating temp and squeez the top radiator hose, if you feel the coolant squeeze out into the motor you thermostat is fine, but if you feel the hose and it feels presurized you need a thermostat. Also check to make sure the fan is operating at operating temp because that would cause overheating. ALL vehicles require the cooling system to be bled. Some have a bleeder screw (usually near the thermostat ) if not fill the radiator and keep toping it off at the coolant tank.
SOURCE: no heat bottom radiator hose stays cold and top
You either have some kind of blockage like a plugged radiator or a colapsed hose, or your water pump is not moving any coolant. It's not very common, but it is possible of the impeller inside the pump to come off of the shaft or become so coroded they dont't move the water anymore. (very rare) What you are describing sounds like a plugged radiator, if you can see the tubes at the top of the core when you have the cap off and they have a lot of blockage then they will be like that all the way accross. I have had limited success with store bought chemical flushes from the parts house and a new radiator for this truck is not very expensive and the are super easy to replace.
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