No coolant circulation

2008 MAZDA 626
116,000 MILES • 2.5L • 4 CYL • 2WD • AUTOMATIC
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ERIC30
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Had a leak in the radiator, so took it to a shop. They replaced the radiator, thermostat, hoses, and water pump. Upper hose gets hot, but lower hose stays cold, so I replaced thermostat two more times and radiator again, same problem each time. They did pressure test, no leak down, so head gasket is good, no water in oil either. When running and warm It builds up pressure, but lower hose still cold. I had no problems at all before. I am no mechanic, but sounds like bad thermostat. But can three be bad? Third one was a Mazda thermostat. Also, burped system numerous times. Both the shop and I are stumped. Any ideas?
Jan 9, 2018 at 4:42 PM
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STEVE W.
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Okay, so the only issue prior to the repairs was the leak in the radiator correct? They replaced the water pump, radiator, hoses and thermostat and then you have this issue. You replaced the thermostat and radiator again. I would check the hoses first, it is not unheard of for one of the caps on the new radiator to be left on by accident and block the flow.
Next check the water pump, first be sure the belt is driving it in the correct direction, if it is, remove it and verify that the impeller is also turning and is the correct direction as well. Also, check the impeller to coolant passage for clearance issues. I have seen more than once that a replacement pump had been assembled wrong and the inlet side had excessive clearance. That basically means the pump just pushes the water around inside itself with very little flow through the system.

Also, could you verify the vehicle year/make and engine please?
Jan 9, 2018 at 8:27 PM
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ERIC30
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After more time at the shop, they determined that the head is cracked, so I dropped the car off at another shop to get another opinion.
Jan 10, 2018 at 3:44 PM
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STEVE W.
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If it is getting hot real fast and building pressure a bad head is possible. A combustion gas test would show that.
Jan 10, 2018 at 5:31 PM
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ERIC30
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First estimate was $3500, an looking for another.
Jan 13, 2018 at 2:40 PM
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STEVE W.
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Is that for just head work or replacing the engine?
Jan 13, 2018 at 8:08 PM
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ERIC30
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That is for head gasket, machine work on head, plus timing set and labor.
Jan 13, 2018 at 8:14 PM
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STEVE W.
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You might want to see about getting a rebuilt head, could save you money overall.
Jan 14, 2018 at 7:41 AM