Thread: Engine running hot on Highway?

Providing that the thermo clutch on the fan is working,you will probably find that the radiator needs rodding.It doesn't take much of a restriction to raise the temp.

Wayne

Firstly this is an indication that your engine is not being adequately cooled - you mention new pump, coolant and rad rodded so it pretty much leaves the viscous fan or some internal blockage / head gasket issue.

Essentially defender cooling is close to its limit when functioning at 100% which is why regular maintenance is vital.

It is interesting to see the coolant temperature variation (using a proper measure - not the dodgy factory gauge) depending on vehicle speed. Low speed and up to 80ish km/h fenders are in the sweet spot and will stay cool even if having a compromised cooling system. But, then once you are up around 100km/h, there must be some level of air flow stalling over the rad and unless you have a working fan you get heat loading and rising coolant temps - most notable in high atmospheric temperatures.

Check your viscous fan and then keep hunting down the problem - temps can be stable at 100ish - just need everything working!

Steve

It's stable, it's just that it's sitting a bit higher than normal when on the highway at 100kmh +.

I would had assumed at 100 it would be cooling even better. If you say 80kmh is the sweet spot, maybe it's doing what it's meant to?

G'day fender22,

I had a similar problem with my V8 County. Turned out to be a worn out viscous fan.

Edward

Is there anyway I can check the fan coupling myself? Is it hard to replace?
I see they're around $200 on ebay, wouldn't mind replacing it anyway as a first step and if there's still an issue I'll still be glad I did it.
Nothing I hate more than potential cooling problems!

You didn't say if it was a radiator specialist or yourself who replaced the coolant and flushed the radiator.

In my experience, while the radiator may have been "flushed" and have had the coolant replaced - this does not mean that it does not require "rodding" (tank removal and tubes cleaned) as LowR suggested in the 2nd post.

This should not be expensive - abt $100 probably (providing the pressure test that they will do does not reveal any other problems which you would want to know about anyway).

You can easily remove the radiator and take it in and save a bit of labour $s, alternatively you can take the vehicle in and they can pressure flush the block as well which can be a good idea.

Well I think that's what I'll do. Just had a good look at the viscous coupling and it spins easily when engine off but there is an amount of drag there, feels about right. The fan is spinning well at idle speed, good airflow and stops dead as soon as the motor turned off.

BTW, that bottom radiator hose clamp (to the radiator) looks like a ****** to get at?

Originally Posted by fender22

........BTW, that bottom radiator hose clamp (to the radiator) looks like a ****** to get at?

depends a bit on how and who put it on - for example they may have tightened it from underneath and not planned for easy access - (you won't have to worry about it if you take the whole vehicle in)