Hi i hope someone can help me , my car started overheating recently , so i took it down the garage the mechanic cannot seem to find the fault , the problem is the fan that cools the engine does not come on when the temp rises , anyway we checked everyother thing , we replaced the fan switch which we thought was the problem , and still its not working , we connected a jumper and the fan does come on when directly connected , we checked for leaks theres no leaks anywhere , we suspected the thermostat but so far we think its working , because we get the top hose hot and bottom cool as well as the heater working on all levels, the ac when put on does activate the fan that cools the engine , but it doesnt come on by itself , it is 2001 honda accord 1.8 vtec

 

ON the thermostat housing there should be a large temperature switch.
Unplug the switch, turn the key to run but do not start the engine.
Use a paper clip to bridge the 2 pins in the harness connector you unplugged.
Radiator fans should turn on.
This verifies everything can operate if the switch tells it to (checks everything electrical except the temperature switch in the housing).


If there is a breeze blowing through the radiator, that can negate the need for the fans to run.



If the cooling system has lost antifreeze and you had to refill it, there may be a bleeder valve atop the thermostat housing to help burp air out.

Pic of an older Accord, yours may or may not be similar


If the radiator core (the tiny tubes inside it) is clogged with calcium/lime deposits, that can restrict liquid flow to the point of inhibiting heat transfer.

 

I guess I should add that a thermostat stuck closed would cause about the same symptoms as a clogged radiator.

The top hose will almost always get hot, as the thermostat is located in the inlet from the lower hose not the upper.

 

Thank you for the reply , i will check it out ,

 

on top of the thermostat housing isnt that the radiator fan switch?

 

Honda usually put the fan switch in the thermostat housing back then...and I cannot see what your car has.
Is there more than one sensor in the thermostat housing? Does it turn the fans on when you jumper the terminals of the connector?


You are in the UK, I'm in the USA. You have a car/engine combination that we did not get over here.
Plus, you are asking about an Accord in a Fit/Jazz forum.

 

yes i understand , i am sorry i didnt know until after i posted the question that this is a honda jazzforum , i thought i might get some help anyway , yes the fan turned on when i jumped the terminals of the connector , the problem am having is the fan not turning on when it starts to overheat , i have put a new fan switch still made no difference , i dont know if the temprature sensor is causing this or the oil pressure switch , i have bought another thermostat which i will fit on soon as i get the chance ,

 

i have attached an image of ,my engine bay with my question at the top , on my honda the fan switch is located on top of the thermostat housing

 

The way the system is typically designed, the radiator fan switch is between the lower radiator hose and the thermostat..... so as long as the bottom radiator hose stays cool, the fan switch will not get hot enough to turn on the fan.

If there is a circulation problem that prevents flow through the radiator, be it a stuck thermostat, water pump impeller, or clogged radiator, then you would have no fan operation while the engine is overheating because the hot liquid is not reaching the fan switch.

You could boil test the thermostat in a pan of water to see if it will open

You could do a makeshift flow test on the radiator by disconnecting both radiator hoses and using a garden hose to see if it is badly restricted.
It cannot be due to an oil pressure switch. That operates the red oil warning light (the gravy boat symbol LOL) for engine oil pump pressure too low.

You say it is overheating, is that just seen on the gauge?
Does the radiator or reservoir overflow? Boiling out? Steam?

Could the gauge on the dash be inaccurate? Just a thought.
Confirm using a scanner the temperature data agrees with the gauge on the dash??


I was using a phone earlier, now I'm on a laptop and I can see your pic better. I don't remember ever seeing a fan switch sticking straight up on our Accords over here.


Thermostat is probably the cheapest part to toss at the car.
While you have the coolant drained out take a look inside the radiator and see if the little tubes inside are clogged with lime and calcium deposits.

 

Thank you very much for all the advice i will try everything on the weekend and get back to you,there is possibility of the gauge being faulty but i am pretty sure we crossed it off the list when it was getting checked out by my mechanic friend , hope you have a good weekend ,