Radiator is half hot & half cold

[direct2000]

This is exactly my problem, it suddenly happened today
(years ago if engine was overheated, then a fan started until temperature went down = Honda CBF500):

the right part of the radiator is hot while the left part is cold, Temperature is going up to the red zone but the fan does not start
Maybe termo switch is on cold part of radiator and because lack of circulation does not let a fan to start?

What is the reason? Should I buy a new thermostat?
Level in 'coolant reservoir' is normal and I added a bit after.

[lihp]

faulty thermostat, or possibly blocked radiator, either by debris or air.

Remove and flush out the radiator and see if there's any improvement.

Additionally, it isn't uncommon for one side to be cooler than the other, as the water goes through the cooling process, so goes in hot comes out cooler.

[direct2000]

I think there is faulty thermostat or some air in the radiator due defective radiator cap which causes no circulation.

These thermostats can become corroded and worn causing the engine to overheat, or even run too cold! If in doubt replace this item with a new part, and save the higher costs of repairing a damaged engine through overheating.

•Helps keep the engine at the optimal operational temperature
•Renewing this part could save money and much more expensive repairs if the old unit fails!

[direct2000]

How can I check that a pump is working?
Today morning I have checked by riding near home. Temperature was low for a while and then suddenly went up.
Right side of the radiator was very hot but the left side where thermo gauge/fan sensor attached was absolutely cold.

I think thermostat is closed and all circulation goes through engine only so it being overheated rapidly.

[P.addy]

[direct2000]

I've found info on this forum but affraid that is about central heating radiator:
"if it's been mentioned already, but if the radiator is cold at the bottom then it means there is crap in the system, if it's cold at the top it means there is air in the system. "

[bikenut]

:D hi dude,

remove thermostate, flush flush and flush again ALL system.

reassemble without thermostate and run engine.

with rad cap off and eng cold, does water level drop slightly ( and give an indication that water flow is taking place )when revs rise to say 3krpm.

when at running temp with rad cap on, stop eng, any cold patches in rad core??if so then those tubes are blocked. allow to cool before removing rad cap!!!!

test thermostate etc.....if ok reassemble system properly.

fill system and bleed........run and feel rad at bottom and top, feel thermostate opening by temperature or is system opening thermostate backwards?? ( coolant gets hotter etc but thermostate dont open till hot coolant passes thru rad backwards then opens thermostate??

when all ok and u happy, refill with antifreeze/corrosion inhibitor.

sacrifitial anode in your cooling system??

[Walloper]

Don't call it a thermostat. It is easier to think of it as a temperature regulator.
It is closed when the engine is cold so coolant is kept in the block and circulated via a by-pass circuit to help the engine warm up to 'running temperature' Engines work better at this temp (82C) as all the bits have expanded to fit properly. And fuel mixing works better.

The regulator then gradualy opens as the heated water warms the wax in the regulator bulb. It pushes a piston out of the wax and opens the valve.
Coolant is then directed to the top of the radiator.
It should be hot at the top and cooler at the bottom.
There shold be a drop of about 10% between top and bottom over the complete surface (when the fan is blowing air through it). Less than this means the system has a fault. Not enough flow.
Pumps are robust but regulators feel heat all their life and can fail.
If only one side of the radiator is hot it means something may be blocking it. Before ripping it all apart drain and fill with fresh water and a radiator cleaner.
Do NOT leave the bike in the cold with this shit in it as it can freeze and fuck the engine.
There are some cleaners that can be added to a frost protected system and run for a few days to act on the system.

Buy good quality Antifreeze. It will come premixed 50:50 with de-ionised water and have 2% inhibitor from the factory It will (should) state this on the bottle/can.
____________________
W-ireless A-rtificial L-ifeform L-imited to O-bservation P-eacekeeping and E-fficient R-epair

[direct2000]

[Walloper]

[direct2000]

[quote=No. I mean a water temperature regulator. Which controls the flow of coolant around the engine.
A 'an switch only controls the temperature at which the fan comes on.

They can be electrical, hydraulic or even a bi-metalic strip which closes a valve and forces a viscous fluid through an impeller/turbine affair to drive the fan.[/quote]

Are you sure that I have this water temperature regulator on my bike Honda CBF500, 0.5 Litre? This is not a turbo-disel engine. I suppose the thermostat (with a pump) is for this purpose.
Have you got a bike or a car?

PS: This this temp (82C) typed on the thermostat which I ordered which fits to
Honda CBF500, CB600, CBR600, VFR750, CBR900, RVF750, VF750, XR650 &
Kawasaki GPZ400S, KLE400, EX-4, KLE500, ZX600, ER500, GPZ500S, ZX500.

[Walloper]