my myvi engine temperature started going up when during on the hill, to be exact when i on the way to bentong. which pass by the karak highway genting sempah.
i straigtht away switch off the air cond and the temperature going down .
driving in town during traffic jam and idle all seem normal.

i have service the radiator but on the way back to KL it having the same issue.

anyone encounter this before?

FAN, Radiator or thermostat

Could be waterpump or radiator fan

This post has been edited by ledtechn: Jan 6 2019, 11:19 PM

Check coolent levels, pump and radiator fan. Make sure all the parts are clean and unpainted as well even the front grill.

Best way to test, in the hot sun put the aircon to full/max, how cold is it? also how hot is the radiator? If the radiator is not hot then you have a problem with the coolent/flow. A hot radiator means that the cooling system is working well since the delta between engine and radiator is lower. In modern cars the radiator is typically a centralised cooler for many different parts, so the flow bit is important too same with coolent levels, check it regularly if you are having problems as well, you can also do a coolent system flush and make sure there is no dirt or anything stuck inside.

Make sure you use both the proper coolent and right engine oil.

i just change the thermostat few months back.
after services the radiator still the issue happen.
fan is working fine during city drive. will it only failed during going uphill?

waterpump? mechanic said coolant no leaking. and noway to chek its condition.

Air cond is ok on the hot sun.
Already service the radiator but still it happen again only during uphill.
checking coolant level and still the same...meaning no leaking.

Some ppl, car hit 100k km immediately change waternpump regardless its condition
It is called preventive maintenance.

To check it need to remove it. Because the blade inside might be gone already due to corrosion. So it is not pumping enough coolant at high engine rpm and causing overheat.

Try this:

Ensure coolant level is correct.

Proceed to go uphill til you notice the temp is higher than normal.
Check the engine bay for any signs of coolant (try not check this as fast as you can, before it dries up)
Sometimes minor leaks, and will worsen when engine is under load (eg; going up hill in your case.

I faced this issue previously, no signs of leak until engine under load uphill, then there is coolant squirting from one side of the rad.

I'd start with the cheapest fix: change radiator cap. Make sure you get the one with proper pressure rating.
Old cap may not be able to hold pressure.

Change radiator directly, flushing radiator sometimes doesn't resolve the issue.

Could be the Radiator water hose. Got a friend had same problem on his 1st gen Myvi, eventually was the Hose collapse/flatten, water got restricted and couldnt flow properly.

But what about coolent flow, make sure you check that.

Other than what one above mention where hose flatten, check that theres no blockages and check the pumps, service/change them if needed. It really just sounds like you're lacking coolent flow.

check thermostat and waterpump next

Ok.. Will try to change the water pump and see how..

Might just change the hose as well is change water pump

I expect it to be the opposite. Cranking up aircon fan should cool down the temp kan?

I think you need to bring back to the mechanic... clearly something not done right when he replaced the thermostat / service the cooling system.
My guess is maybe cooling system bleed wasn't done until all air is released.

I think you confused aircon with heater kan?

Send for other mechanic to check.. He said might be engine gasket head blown.. No way to checkto confirm.. Just guessing..

Dipstick got kopi susu appeareance or not ?

https://www.youtube.com/watch?v=3suQy44G_B0 ,

Engine got overheat before? Burnt gasket?

top overhaul 2 years ago due to overheat.

dont see any of this sign//

My previous car had similar issues.
Water pump, fan, thermostat, etc all ok.

Finally found the culprit.
It was the radiator .. clogged up with dirt that air flow their the radiator fins were affected.
Cleaned the dirt off using water spray.

Problem solved.

Coolant will pass through the radiator channels and the fins is to remove the heat and air flow through the fins remove the heat from the fins. If airflow is not efficient or blocked...heat is not removed from the coolant.

Could it be the water buble inside the radiator? Try reflush the old coolant and put new coolant n water and ask mechanics to ensure water bubble is eliminate

nope. Older cars the aircon is separate so requires more power from engine. Modern cars the aircon is integrated into cooling system so it takes cold from the system making it work harder.

changed water pump and hose, yesterday pass by karak highway, drive slowly and engine temperature didnt go up high this time.
assume issue solved for now.

updated: seem like under heavy load during mountain climbing, temperature slightly go up a bit.. is it mean engine gasket issue?

This post has been edited by dinor01: Feb 10 2019, 09:15 AM