Overheating when under load

[Oompaloomp]

Hi
Recently noticed temperature gauge going up when engine is under load, such as going up an incline or motorway driving. Goes from the usual half way point to just touching the red. When the load is reduced or I pull over with engine running the temp gauge goes back to half way. Not losing any coolant, heating is working, top rad hose gets hot. any ideas or suggestions gratefully received as I cant work it out!
Thanks

 

[Enuo]

Clogged radiator?

 

[Oompaloomp]

That was a thought. Planning on flushing system. Hoping it is something as simple as that.
Thanks

 

[Oompaloomp]

Also noticed that bottom hose of radiator is hot but radiator feels cool. Should'nt bottom hose be cool?

 

[pollyp]

check the cooling fins cos every cm3 of bent or blocked fins will degrade its cooling ability.
check the thermostat is fully open at 82c on a pan of boiling water.
reverse flush the cooling system from any old debris.
and reverse flush the radiator.

 

[Oompaloomp]

Thanks Polly. Do you have a link to one of your posts for an idiots guide to this?
Thanks again

 

[frank]

Thanks Polly. Do you have a link to one of your posts for an idiots guide to this?
Thanks again

paul has a very useful index on his blog

 

[pollyp]

suggest getting a haynes for detailed instructions how to remove the rad & thermostat and flush the system.

for testing the thermostat I have a video here
http://micra.org.uk/threads/pollymobiles-rebuild.35251/page-95#post-633626

 

[Oompaloomp]

Well I'm running out of ideas now. Flushed rad (good flow, no crud). New thermostat. Back flushed the system. New antifreeze. Ran at normal temp for about 150 miles, then old problem returned with overheating going up long inclines and under load.

 

[frank]

is the fan kicking in ?

 

[Micra1.3lx]

I maybe wrong but it could be a symptom of a failing pump, ive known in extreme cases for the impeller , or blade to disintegrate, yet the pump shows no outword sighns or makes any noises. Just a thought

 

[Oompaloomp]

Frank - I,m not sure when the fan should be kicking in. Theres times when its overheated and when I've switched off the fan's been running and times after I've just driven it normally. Other times the fans not running after its overheated.

1.3lx - No noise from the pump buts its creeping on to the list of suspects!

 

[frank]

Frank - I,m not sure when the fan should be kicking in. Theres times when its overheated and when I've switched off the fan's been running and times after I've just driven it normally. Other times the fans not running after its overheated.

1.3lx - No noise from the pump buts its creeping on to the list of suspects!

it should kick in any time the gauge goes over half mate, thats the 1st thing to check when a car is overheating but not drinking coolant tbh, and the pump impellers are steel

 

[Micra1.3lx]

I didn't say it was the pump, I just said was something to consider.

 

[frank]

you could remove a heater pipe and test the flow, this is the flow suffering from a very very slack belt

 

[petros047]

I have the same problem first i replace thermostat with no luck fan radiator work perfect but the temperature rise when the car run with load.
unfortunately the engine burn engine gasket so I buy new motor.
So try to resolve the problem in a garage and dont test it on road.

 

[NikosRollercoaster]

If the pump is fine there is no signs of blockage in the system meaning there is enough flow and pressure fan is kicking in....maybe...maybe the gauge it self is faulty..try another gauge and see what happens...Γεια σου petros047!!!

 

[Oompaloomp]

Thanks guys. This is probably a dumb question, but where is the radiator fan temperature switch located?

 

[Enuo]

Thanks guys. This is probably a dumb question, but where is the radiator fan temperature switch located?

In the ecu.

 

[r-reg-sr]

Thanks guys. This is probably a dumb question, but where is the radiator fan temperature switch located?

Sensor for the switch is below distributer. 2 wire one