Thread: 3.5 V8 running hot on warm days

Originally posted by discowhite
<div class='quotetop'>QUOTE</div><div class='quotemain'>cant see the point really if thermostat is only opening up a few degrees earlier, once coolant gets hot, it is hot... in my opinion, you can take the thermostat out and it wont make difference.

I second that.
ive run cars with and with out, once its hot its hot simple as that.
no thermostat just negates that it will take longer to heat up the water
system. because there is no valve(thermostat) to stop the water circulating.

if theres a blockage in the radiator this causes back pressure, this will slow up water flow, in turn making the already hot water hotter.

just bite the bullet, sell your mother and fix it properly. otherwise
it will bite you in the bum!

from past experiances.
Phil.[/b][/quote]


sometimes NOT running a thermostat may also cause overheating as the coolant does not stay in the radiator long enough to cool down.
it just goes through it that quick that it just gets hotter and hotter.....until you give it a bit of load then just boils over and spits the dummie

Another issue that hasn't been addressed is the clutch fan. Lock up the clutch fan with a concave washer from a shock absorber in between the retaining bolt ant th front of the fan and go for a good drive on a hot day to see if this is the problem. Also replace your temp gauge if iot is an original one with something after market so you know what temp you are at. Putting in a cooler thermostat doesn't let the water in the rad cool down enough as it doesn't stay in there long enough for the rad to do its job. Go for the standard thermostat if no luck. Try the clutch fan if no luck. Change temp gauge if no luck get the rad rodded and cleaned it is only about $120 before you go spending big money on changing rads. If it is the thermo fan all X flow falcon engines have a similar clutch fan but need to have 5mm trimmed off the end of the blades these are a lot cheaper than genuine Rover parts. If you want go and spend lots of money I have seen Nissan Patrol Rads in Rangies before but I don't know how much moding is required to make these fit.
Just remember all the cooling system works fine when it is in good order so replacing it with bit off other cars will probably cause more headache.
I see you are chasing a snorkel also get one as soon as you can as this will help with cooler air entering the system and not sucking in all that hot air under the bonnet. Mine has improved due to the fitment of the snorkel.

Originally posted by DEFENDERZOOK


sometimes NOT running a thermostat may also cause overheating as the coolant does not stay in the radiator long enough to cool down.
it just goes through it that quick that it just gets hotter and hotter.....until you give it a bit of load then just boils over and spits the dummie

If you do it right it's much the same as the thermostat being fully open and if it still boils then the problem isnt the thermostat.

What you do is take the suspect thermostat assembly out. What you've got is the restrictor and the valve. Cut the valve out so all you have is the restrictor and put that back in. The motor will take longer to warm up but this mod will get you out of trouble in the short term until you put another servicable thermostat in.

Why you just put the restrictor back is as you noted above, there is nothing to control the water flow. Most will happily toddle about the 'burbs with nothing in the housing but it's the highway work that brings them unstuck. The restirctor keeps the water in the radiator long enough to be cooled before doing another lap of the system.

So always stick the restirctor back in there if the thermostats bung and you don't have a spare.


Just on the 100% anti freeze. It's not normally recommended in concentrate form. Reason is on some motors it can be corrosive, cast iron would be okay but these alloy heads and such these days tend to not cope as well and it not really required at that concentration anyway.

I run 50% coolant mix in Hellspawn which is more than enough and she NEVER boils even with a 82ºC thermostat. Comes up to 95ºC occassionally.

If we say no coolant under pressure boils at 115ºC and off my coolant chart 50% boils at 132ºC, 100% coolant ..... the radiator will explode before the coolant boils. 8O