Need help on diagnosis on engin hot problem.

The car is Mazda 626, 1995 with manual transmission. After running for 10 minutes, the engine becomes hot. The temperature is not consistently very high, sometimes it goes back close to normal. I checked cooling fan a few times, the fan always works. It does not look like temperature sensor is faulty. Because when the car just starts, the indicator shows low temperature, which gradually increases as car is running. The temperature stays at normal for a while, then goes higher. I changed thermostat, but found when engine was hot, the coolant hose with thermostat was still cold. So I changed to another thermostat, and found the same thing happening. Now, I am thinking maybe water pump does not work, and coolant does not circulate. so even when thermostat opens, the hot coolant does not flow, and this hose is still cold. Does this sound right? Thanks.

所有跟帖： 

• Make sure thermostat installed in correct orientation -cire622- ♂ (583 bytes) () 10/13/2009 postreply 17:37:49

• Several things -biglow- ♂ (296 bytes) () 10/13/2009 postreply 18:01:46

• I have checked and here is the facts: -wimax88- ♂ (217 bytes) () 10/13/2009 postreply 18:25:20

• put a new water pump if no coolant lost. plastic blades of water -fixanycars- ♀ (91 bytes) () 10/13/2009 postreply 18:50:45

• Then open the radiator cap and observe the liquid flow -biglow- ♂ (169 bytes) () 10/13/2009 postreply 20:43:47

• when the engine is hot, turn on the heater fan -xxhhwxc- ♂ (81 bytes) () 10/14/2009 postreply 07:09:30

• Second xxhhwxc that logged radiator sounds more likely. -QYZ- ♂ (549 bytes) () 10/14/2009 postreply 07:40:37

• this radiator has been changed about 4 to 5 yes ago. -wimax88- ♂ (285 bytes) () 10/14/2009 postreply 08:58:22

• Thanks everyone for your ideas. I plan to take the car -wimax88- ♂ (64 bytes) () 10/14/2009 postreply 09:00:28

• 很簡單 -潤濤閻- ♂ (184 bytes) () 10/14/2009 postreply 17:39:28

• if冷卻水流入氣缸一小部分, you should see white smoke from the tail pipe. -QYZ- ♂ (0 bytes) () 10/14/2009 postreply 19:18:41

• 他的情況是：高壓把氣體壓入冷卻水，而冷卻水的壓力不足以 -潤濤閻- ♂ (256 bytes) () 10/14/2009 postreply 19:26:10

• Then why coolant does not return to radiator through thermostat? -wimax88- ♂ (0 bytes) () 10/15/2009 postreply 08:53:42