Cooling system overheats. radiator stays cool. have replaced everything short of the radiator. any ideas? changed the phlange, water pump, thermostat, radiator switch, fan module, and fan motors. seems to get air bound or not circulate. Mechanic let it idle for three hours without incident. I drove 1/2 hour home and it is overheateing again. Do I really have to take the whole nose off to replace the radiator or is there a simpler and faster way?

flushing a cooling system is the same method as any other motor

do it without the thermostat fitted
or water pump opening

sacrifice an old radiator hose to adapt a garden hose fitting
for radiator flush

air in system fix
your thermostat housing has no air bleed valve
no top radiator cap

old school way
heater on full
run motor till thermostats fully open
burp radiator hoses
wait till water is running up into over flow bottle without bubble
replace cap
turn off heater
correct level in over flow bottle

why still over heating
you fitted everything i would have ... yet still overheat
possibles
leaking inlet manifold gaskets
hose clamps loose
cooling fans spinning too slow
thermostatic fan switch faulty
aluminum radiator is a big one
air ..fins bent or some water channels blocked

or possible head gasket leak

Are the cooling fans coming on ? Go under the hood in the engine compartment , with the vehicle running have some one turn on the A/C , do you see and or hear the cooling fans come on ? Could be the coolant temperature gauge is bad ! How many miles on the vehicle ? Ever have water pump replaced ?

1

Check for a loss of system pressure.
Is there a loss of system pressure?
--
Go to Step 2 yes
Go to Step 3 no

2

Inspect and repair any faulty hose connections.
Does the engine still overheat?
--
Go to Step 3 yes
System OK

3

Check for low coolant protection (-37?°C/-34?°F).
Is there low coolant protection (-37?°C/-34?°F)?
--
Go to Step 4 yes
Go to Step 5 no

4

Test solution. Replace the coolant if necessary.
Does the engine still overheat?
--
Go to Step 5 yes
System OK

5

Check the water pump belt for low tension.
Is the water pump belt tension too low?
--
Go to Step 6 yes
Go to Step 7 no

6

Replace the water pump belt tensioner.
Does the engine still overheat?
--
Go to Step 7 yes
System OK

7

Check for an inoperative thermostat bypass.
Is the thermostat bypass inoperative?
--
Go to Step 8 yes
Go to Step 9 no

8

Replace the bypass.
Does the engine still overheat?
--
Go to Step 9 yes
System OK

9

Check the water pump.
Is the water pump inoperative?
--
Go to Step 10 yes
Go to Step 11 no

10

Replace the water pump.
Does the engine still overheat?
--
Go to Step 11 yes
System OK

11

Check the radiator fins for obstruction.
Are the radiator fins obstructed?
--
Go to Step 12 yes
Go to Step 13 no

12

Inspect and clean the radiator fans.
Does the engine still overheat?
--
Go to Step 13 yes
System OK

13

Check the cooling system passage for obstruction.
Is the cooling system passage blocked?
--
Go to Step 14 yes
Go to Step 15 no

14

Inspect and flush the system. Reroute or replace the hose if necessary.
Does the engine still overheat?
--
Go to Step 15 yes
System OK

15

Check the water pump belt for damage.
Is the water pump belt damaged?
--
Go to Step 16 yes
Go to Step 17 no

16

Replace the water pump belt.
Does the engine still overheat?
--
Go to step 17 yes
System OK

17

Check the cooling fans.
Are the cooling fans inoperative?
--
Go to Step 18 yes
Go to Step 19 no

18

1. Inspect the electrical connector. Replace if necessary.
2. Does the engine still overheat?

--
Go to Step 19 yes
System OK

19

Check the throttle body circuit flow.
Is the throttle body circuit flow restricted?
--
Go to Step 20
Go to Step 21

20

1. Inspect the orifice and associated hose. Replace if necessary.
2. Does the engine still overheat?

--
Go to Step 21
System OK

21

Check for a stuck thermostat.
Is the thermostat stuck in the closed position?
--
Go to Step 22
--

22

Replace the thermostat.
Does the engine still overheat?
--
--
System OK

Two things to check:

1. Make sure you do not have an air bubble in your cooling system. Easiest way is to park facing uphill and let the car cool off. Remove the radiator cap, start the car and let run until the thermostat opens. If there are air bubbles in the cooling system the should be forced out. Top off fluid.
2. Are you sure that the cooling fan is running? When the car is getting hot, open the hood and make sure the radiator fan is actually turning.

try a pressure test on the radiator while it engine is running.. If your head gasket is broken the compression of the engine goes into the cooling system. If the pressure rapidy increases it would indicate a head gasket problem.

Most likely you put the thesmostat in upsid down. Good luck

the cooling systems consists of a radiator, radiator cap, water pump, thermostat, hoses, heater core and sometime a heater control valve that open water lines to heater core. You may need a cooling system flush if water pump, radiator have been replaced. flush the system.change the thermostat and have the heater core checked too if you can get to it.
does the cooling fan kick on to cool the radiator..check that too.replace radiator cap and check cooling fan yourself...let me know if need anything else.
Thanks for using fixya and please vote.

Okay sounds like you have a clog within the system, first of all, drain the whole cooling system, run clean water thought the top of the radiator, look to see when the water comes out nice clear, replace the lower hose if you have a petcock close that, refill the top of the radiator, until it is full, start the engine, with engine running turn your heater, let the car warm a little, then reopen the petcock or loosen the lower hose and let the water draw out a little until is pouring out nice and fast, then re-close the petcock and stop the engine.
try and get 40% of the water out, and replace it with 50/50 antifreeze fill to the right point of the cars specs.

On a water cooled engine... the impeller on the water pump is no longer working correctly. It has probably come loose from the input shaft and is no longer pumping water. You can prove this on a warm engine by filling the radiator to the top and then accelerating / decelerating the engine... if you don't get a change in the water level the water pump is shot.

Kelly

Pretty common on subaru's, try elevating the front of the car whilst bleeding the cooling system.

The only real way to answer your questions is for you to open the hood and look it over. Once it has cooled down, re-fill the cooling system (use water...it's cheaper and to do repair you will need to repalce it anyhow...Once full carefully look everything over to find where the leak is.Also make sure that the drivebelt is there. (from what you said, likely it is) If it's water pump, you will see coolant running out from under the pulley. Once you have looked everything over, if you have not found leak, start engine and close the cap...look again...as pressure builds, small leaks will become more obvious. If you don't find leak, remove the thermostat and change it.
After changing stat, if problem persists, it's likely that you have either a plugged radiator or an internal engine gasket problem. If you have any auxiliary electric cooling fans, make sure they are working and also check the fan clutch on the mechanical fan (it should not excessively freewheel when hot). Whole testing, any time you replace the radiator cap you must allow engine to cool down before removing it again. Watch temp gauge while testing...don't allow engine to overheat.