Thread: Water temp spiking on hills...what to look for

Viscous fan. Be quick easy place to start.

My Disco had a similar issue

at 110 fully loaded I would see the temp gauge climb back off to 80/90kph and temp would drop back to normal

Could never get it to happen with no load in/behind the car. The way it was put to me was the radiator was likely partially blocked and the back preasure combine with the high pump rpm was causing cavitation and once that started pumping efficency dropped dramatically. Back off the rpm and cavitation would stop and it would be moving enough coolant again to keep it cool.

Fast forward a couple of months got the radiator flushed and rodded out(40% Blocked) and on another long trip even more heavily loaded there was no sign of the previous issue.

'Fred' (D1 300TDi man) is doing the same, with the exact same symptoms.
Changed the viscous fan hub over with a second hand one and that was a bit of a improvement.
Still noticed the temperature rising when we went up through Black Charlies Opening on the way to the East Coast last weekend, so the radiator will be removed next to get rodded out.

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Originally Posted by muddymech

Viscous fan. Be quick easy place to start.

How does one check the viscous fan??

I'm wondering if I need to remove a land rover badge from the grill...

Gave her the once over, no water leaks and level has not moved

I do have an oil leak on the side of the motor....vac pump maybe? Noticed a film of oil on the camper trailer.

Will check viscous fan once armed with the knowledge

thats not dangerous depending on the cooling mix your using.

the boiling point of plain water at 14psig is 119 degrees

the boiling point of most coolant mixes at atmospheric pressure is about 104-110 (varies with brand and concentrate)

I would be starting with checking out if theres any airflow blockages to the radiator ( I see about 3 a year with the gap between the condensor and the radiator full of mud) the Fan VC, the operation of the thermostat (if its only partially opening you wont get full coolant flow through the radiator), the condition of the radiator (if its restricting flow again you wont get full flow through the radiator)


If fault finding shows it to be a blocked radiator, Dump the coolant, flush the whole cooling system with tap water as best you can, put in a cooling system cleaning/flushing agent and then take it into a shop to have the radiator Rodded/recored as appropriate and tell them that while they have it you would like a new thermostat installed and a pressure flush or back wash (essentially the same thing but it depends on where/who taught the bloke) as you have a cleaning agent in there at the moment (be sure to provide them with the bottle for WHS reasons) Make sure that you have all the details for the vehicle including the type (ethyl-glycol, OAT, HOAT, soluable oil) of coolant that you want to have put into the system.

A word of caution.

If the radiator cores are blocked there is a VERY high chance that the cores of the heater matrix are in the same condition as the radiator. If the bloke doing the rodding complains that they are rotten and this is a sod of a job and damnable landrover parts etc etc you would be wise to have a short section of bypass hose made up to deal with the heater matrix failing.


the quick check for the VC is with the engine cold try to stop it with a bit of cardboard after the engines been idling for about 30 seconds, it should stop quickly, then repeating the test with the engine warm it should chew up the cardboard. You should also check the security of the hub on the drive spindle, if its got any rock in it its US.

A bit of a search tells me I should be able to push the fan around by hand it it should stop pretty much as soon as I take pressure off.....all good

Radiator is clean, condenser has a couple of bugs other than that it looks good as well

Will see how it behaves tomorrow

Oh heater matrix is already bypassed