All: Recently replaced my thermostat with a toyota genuine part for my 2000 Camry (4 cyl and california emissions).

I noticed the temperature between the two radiator hoses to be considerably different....the lower hose (goes into thermostat end) gets warm but not hot like the upper hose coming off of the top of the radiator. I notice the car temp runs consistently in 192-198F range. The fans do turn on briefly once temp rises up well into the 190s.

I ended up taking out the new thermo to 1) ensure I put it in in the right direction and 2) to ensure it was opening correctly. On #1 it was correctly put in with the pointy end sticking forward. On 2, I placed in a pot of warm water and heated it up using a thermometer to monitor water temp. Sure enough the 82C thermo clearly opened up around 180F. So, I reinstalled and filled with fluid and pumped the hoses by hand to clear air and added until the system appeared to be full.

So, is the hose temperatures (via hand) variance an issue...(i.s., should the hoses be about the same temps? If so, it would seem to me that more fluid is getting through the top hose than is moving through thru the thermostat hose. Thoughts?

 

Was the air vent hole in the T-stat flange in the up position?

What position is the temp gauge needle indicator when the engine is at normal operation temp? Does the needle move once the engine at this temp?

When do the radiator fans come on?

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Joey:

Was the air vent hole in the T-stat flange in the up position? not sure what this is/means.

What position is the temp gauge needle indicator when the engine is at normal operation temp? right smack halfway between cold and hot, or exactly where one would observe the temp gauge to be in a normal operating condition. Does the needle move once the engine at this temp? no, even on my scantool (OBDII laptop display) when the engine temp range fluctuates in the 180's and 190's...even into the low 200's the temp gauege on the cars dashboard does not move all that much and certainly not near "Hot". It just strikes me odd the the lower radiator hose is not near as warm (near hot) to the touch as the upper hose.

When do the radiator fans come on? if the car is at idle in the driveway (no load) it will heat up to the 180's into the 190's after a few minutes of running. I can hear and observe the fans kicking on once the temp hits the upper 190's or into the low 200's. Once that happens, they run for maybe 15-30 seconds and kick off....there's a slight delay in my scan tool but I do observe the engine temp to as a result (to like the high 180's/low 190's), so the fans do come on and do have some impact.

Maybe this is normal and no issue whatsoever, but I'd be curious if you, or others observe this radiator hose temp difference I describe in your vehicles(?)

Respectfully,

 

Based on your replies the coolant system is operating normally.

The purpose of the radiator is to lower coolant temp. The top hose (coolant out of engine) should be hotter then the lower hose (coolant into engine). How much depends temp difference between hoses depends on outside air temp and air flow, coolant flow, etc.

When the car is stationary or at slow speeds the air flow is minimal, then the fans move the air. If they did not does this the engine would over heat.

 

Thank you Joey....your explanation makes perfect sense!