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silky16v

Member Since: 11 Aug 2014
Location: Cumbria
Posts: 99

2001 Defender 90 Td5 X-Tech LE Blenheim Silver

TD5 new radiator gauge on dash hardly moves, viscous fan?

Hi just completed this weekend in replacing my clutch and flywheel and while the engine was out i fitted my new radiator (it is 10mm thicker core size and is all aluminium no plastic ends) the old radiator fin's where knacked at the bottom and started to flake

Also fitted new Aux belt & new intercooler

once all back together filled coolant system with 50/50 mix of the red antifreeze type and then started the car heaters on full hot and then let it bleed the air from the top screw ran for around 30 mins temperature gauge on dash didn't move out of the blue but heaters are nice and warm, no pressure in system

what i did notice was the viscous fan seemed to be moving a vast amount of air and was alternating its speed even at tick over, so stopped engine and checked the fan which i can turn by hand but has some resistance, but in it full rotation around a 1/3 of it seems easier to turn then goes tighter again?

anyhow left the car overnight topped up the header tank and went for a drive sat at 55mph heaters nice and warm and the dash gauge is now only just on the first line after the blue mark, so pulled over checked water level all is good and no pressure in header tank at all.

so this morning before i set off to work, checked the fluid all good, no pressure no coolant loss, viscous fan still has resistance when cold, there is about a 3mile stretch of dual carriage way so sat at 65mph and the gauge on dash move up just above the line above the blue, heaters all nice and warm, pulled over to check and no pressure in header tank and no signs of any air in system, water in header tank plenty hot enough.

Before the radiator change the temp use to sit just below 1/2 way once warm and heaters where a little warmer

is this right for the viscous fan to have any resistance when cold?

And because i've changed the radiator for new the cooling affect is now far move efficient, thus the gauge not moving as much?

i'm going to try and remove the viscous fan and see if this has any affect, which i suspect it may have? but don't want to buy a new viscous fan (if suspected to be on its way out) because of the radiators new efficiency the car won't come up to temp at this time of year?

any thoughts/help

17th Nov 2014 10:17am

munch90

Member Since: 26 Oct 2013
Location: guildford
Posts: 3558

could be two things

1: engine will not get hot with the heater fan running , heater water is taken before thermostat , with engine doing no work just tick over then it wont make enough heat to get hot to show on a gauge
leave it running without heater fan blowing , heater control on hot , only put fan on to check there is hot air as that shows water is being pushed round then turn fan off again , this way you should see movement on the gauge but doubt your get anywhere near running temp without engine under load or even if your driving gently with fan on full speed it may be enough to keep temp down , turn fan off and see if temp goes up to normal

2: thermostat stuck open ( if temps were ok and doing wot its ment to do before then should be ok ) if temp before was pretty steady as in not rising and falling between moving and stationary , if it went up and down change thermostat

if the thermostat is doing what its ment too, it doesn't matter if you got a rad a mile wide it will get up to temp , the stat is really a control valve it should open only enough to allow enough water though to keep engine at running temp

17th Nov 2014 10:30am

silky16v

Member Since: 11 Aug 2014
Location: Cumbria
Posts: 99

ok will try option 1 as i've always had the heaters on low or medium on hot as it's so cold at the moment
will try at idle and when driving

temps before where fine no movement in gauge needle it always sat at just below 1/2 once warm

only thing i've not checked is the pipes by the thermostat if they are getting hot both sides of it, but i guess it would've blown a pipe by now is the stat wasn't opening?

all other pipes are fine the top pipe with the bleed screw is hard to touch once engine is run up and i can squeeze this a little and its nice and hot

17th Nov 2014 10:57am

silky16v

Member Since: 11 Aug 2014
Location: Cumbria
Posts: 99

still no joy tbh ran without heaters on for 10 miles and then done a spirited drive for another 5miles and the gauge went ever so slightly higher, put the heaters on and it was warm but no where near nice and toasty warm.

checked all the pipes they are all hot and can touch them fine no pressure in the system, both sides of thermostat fine as well and can touch them without it burning my hands

so going to order a new thermostat as i guess it has stuck open

18th Nov 2014 10:51am

mk1collector

Member Since: 17 Sep 2009
Location: West Yorkshire
Posts: 6769

Sounds like an airlock to me. Take the radiator cap off let the engine get up to temp slowly then open the screw in vents till water comes out and retighten then rev for 5 mins or so (all with the heaters off) then put the cap back on and see if it's any better.

18th Nov 2014 11:26am

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