96 Outback Overheating

[Willie]

I just had my timing belt, water pump and thermostat replaced at 120k miles. A few days after this work my car started overheating. Took it back to mechanic and he thought there was air in the system. He bled the system. Still overheated (not regularly), so he replaced thermostat and bled system again. I am now always overheating after going only about 5 miles on the road. I tried bleeding the system myself (running at 2500 rpm for 5-10 minutes) and the car never overheated. After getting back on the road, 5 miles and the car overheats. Could this be a radiator problem? Two mechanics have told me no way on a head gasket or cracked block. I am stumped!

 

[Carl 1 Lucky Texan]

are you losing coolant?
If you want to, try putting the front up on ramps (or the curb or
someething), TURN THE HEATER ON MAX, open the radiator and run until
hot, make sure there is plenty of coolant in the overflow bottle and the
rad., put the rad cap on, allow to cool. Monitor the o'flow for severla
drive cycles, IT MUST NEVER BE DRY. You didn't mention if the rad cap
was replaced (they usually are when a new t'stat is insatlled) make sure
you got a new one. Some folks claim it takes 600 miles of driving to get
all the air out. Does your exhaust smell sweet? Did the mechs actually
test for combustion gases in the coolant? Better insist on it if they
didn't.

Carl
1 Lucky Texan

 

[Willie]

Coolant is being forced out of overflow by air
buildup in the left side of the radiator. The last time I
had the car I ran until hot, stopped the car, released
the air/steam through the bleeder valve on the radiator. I left the bleeder valve off and during cooling, the radiator was still sucking fluid from the overflow back into the system.
How could this be possible?