Hi All,

My 1989 Hyundai Excel (1.5 ltr, 4 cylinder, carby model) tends to run hot when idling for a while. When travelling in excess of 60 kms/hr, the temperature is close to normal. The radiator cooling fan and cooling fan switch checked out ok. The radiator cap looks ok. Could it be the thermostat? What other checks should I perform on the cooling system? I do not have a cooling system pressure tester but could arrange to have this done. Any hints or tips would be appreciated.
Thanks

Mike

 

make sure the coolant level is full and that the cooling fan cycles on and off when idling.
is the engine actually overheating.
it is common for the temp guage to read slightly higher when idling as you have no airflow to reduce engine temp until the fan comes on.

 

If Bejay's advice checks out ok, replace the thermostat. It should be easy and cheap to do and could be the cure.

 

Hi

Thanks for the advice. I will change the thermostat as this is the cheapest and quickest thing to do at this stage. The coolant level is ok. I did mention that the cooling fan does not operate at all even though I have checked that it is ok by shorting the switch terminals. I have also checked that the switch is ok as it switches on at approx 88 deg C and switches off at approx 83 deg C, as per the specification, when tested in water with a thermometer. Appreciate any further advice. Thanks

Mike

 

At 1st you said the radiator cooling fan and cooling fan switch checked out ok. I thought that meant the fan was operating. If the fan isn't working at all then that should be the reason for overheating. You need to find out why the fan isn't working. Is the coolant level full?

 

Hi,

The fan and switch check out ok as mentioned i.e. when tested separately. However, I feel that the water temperature in the radiator bottom tank (where the switch is fitted) is much lower than that in the engine, that is why the switch isn't operating. I assume that either the thermostat is remaining closed, or possibly a blockage in the radiator. Will have to do some more checks on thermostat, water pump etc. Thanks

Mike

 

...radiator hose gets hot, the stat is working. if that's the case then the top of the rad will also get hot...like too hot to touch and your problem is the radiator...the rad should be cooler at the bottom, but hot enough to reach fan switch "on" temp. the easy way to verify this is with a infrared thermometer. a little expensive...but VERY accurate

 

... to check the cooling fan relay. I'm not an expert, so I'm not sure where the relay would be. The switch is good, the fan works, so that leaves the relay, wiring between everything, and possibly a ground problem. I kind of doubt a ground problem, but you never know! One last thought... maybe a fusible link???