Hello to all,
After I drive the car and I turn off the engine, the radiator fan stays on for 1-3 minutes once in a while.
Sometimes I hear the reservoir water boil. But the car does not overheat, temperature gauge stays in the middle.
Is this normal? or I need to be concern of a problem with the cooling system.

 

The cooling fans come on when the coolant is over a certain temperature when the car is turned off. It is normal for the fans to come on for a minute or so. When the engine is cold, take off the radiator cap and make sure that the coolant level is pretty much to the top.

If the antifreeze hasn't been changed in a while, then I would buy some of the radiator flush and run that through the system to remove any deposits. Then run water through it several times for about ten minutes to remove any residual crap left from the flush. Replacing the thermostat with an OEM one from the dealership would be a good idea, since you are changing the coolant. Refill the system, bleed any air by opening the valve on top of the thermostat housing, top off radiator and fill overflow tank, and you are done.

 

On top of PAhonda good advice,,, if coolant is low , pressure test the system to chk for leaks . also, test the radiator cap , make sure that it holds pressure, If you indeed hear water boiling than something is not right with the cooling system,, it is overheating ..and yes , you do need to be concerned and fix it ASAP..

there is a write up on our DIY section about overheating ..chk it out

 

something is wrong. the radiator fans do not come on with the car off unless the secondary fan switch tells them to. this means the coolant tempthermoswitch(A) that controls the cooling fans located in the thermostat housing is probably sticking or completely inop. it should open at 194F and cool the engine like normal.

the second thermoswitch(B) is located where teh upper radiator hose connects to the cylinder head. this is the switch causing your fans to come on when the engine is turned off. it is probably the only switch operating the fans while the engine is running. it's designed to turn on the fans after 226F. this is obviously MUCH hotter than intended.

if i were you i would test the thermoswitch (A). if it's bad i would replace that switch, the thermostat and the coolant. i'd also inspect the radiator and hose condition and replace both if necessary.

check the radiator for corrosion. you don't want to see any seepage or wetness anywhere. you also don't want a ton of fins missing or fanning out(you'll know what i mean if you see it).

the hoses shouldn't be soft or spongy, they should feel tight and firm...(oooo la la)

 

One small concern with pressure testing the system, sometimes when you pump your hand pump pressure tester up to the cap limit, lets say 15 PSI and it holds good, it is very possible that lets say the water pump will not leak until the pressure comes down to lets say 10 PSI such as when the car is cooling down normally. Are you quite sure that you dont have any leaks in your parking spot. If not then do as mentioned above, if a new OEM tstat does not fix it up then start inspection for a blown head gasket.

Thermoswitch A and B work as explained above, the fan can be controlled, by a timer, for some time after the engine is shut off, this is normal, a bad timer has been known to kill batteries in the middle of the night, yours sounds good.

If there is no actual liquid coolant touching the temp sending unit, then your temp gauge will not show overheating, it does not registar hot steam until its extremely overheated so beware of this scenario. Again, if you squeeze a radiator hose and it sounds like it is crumbling on the inside, the entire system will need serious maintenance and a head gasket leak kit used to test for it, I think it tests for CO.