420r temp and fan question

[Tommyp]

Not had my 420r for that long before the lockdown so been limited running. I noticed a few times when I took it out that the temp gauge seems to stay stable when going along at fair speed, including on motorway 85-90, but it seems to start rising pretty quickly once sat in traffic, will be going up to 100, it's hit 105 before moving off again and coming back down. I can't tell if the fan is kicking it - should I be able to hear it on idle when sat in the car?

is this temp fluctuation normal on these and what temp is the fan meant to kick in at? 

I'm used to a bit of fluctuation on my air cooled 911 but thought these modern engines would cope a bit better with a bit of traffic/idling

 

[ChrisC]

Assuming your car isn't a very early (2015) 420R, the thermostat in the standard Ford part for a Duratec meaning it opens at 102C. Before that temperature was is circulating through the bypass circuit and not the radiator.   The ECU operates the fan at 105C.

To complicate things the gauge and the ECU use a different sensor, so there can be a little discrepancy between the gauge and the fan, but it sounds like yours is spot on.

I am not sure why the Duratec can cool sufficiently without the thermostat being open when on the motorway, and what the effect is in reality, don't forget the coolant is circulating, the oil is being cooled (no thermostat), and the ECU would be running the fan if there was a problem.   

Older cars had a 82C stat and a 97C fan kick in point, but your car is maintaining that temprature without problem.    

So it sounds like your car is perfectly normal to me. 

 

[Tommyp]

Thanks the reply, that's good to hear. Yes it's a 2017 model.

hopefully can get it out on track at some point this year

 

[Martin_mad]

I had an issue with the radiator cooling fan not cutting in (new kit). The problem was located to a loose female spade connection on the relay housing block (green wire).

[Tommyp]

Will double check that too

[7 wonders of the world]

Chris the stat will be open whilst cruising at motorway speeds, it position is simply controlled by the water flow form the radiator (cool) and from the bypass (hot) and it shuttles in order to maintain temperature closing the bypass circuit off when its fully open and closing the return line of when fully closed.

Water pump speed is the reason the Duratec seems to run cooler at cruising speeds as in its original tin top application the engine rpm would naturally be less then Caterham run for a given road speed

The pump becomes less efficient at the upper end of the rpm limit and can lead to cavitation on engine regularly seeing 8500rpm which is the reason the pump is slowed by using and oversize pump pulley or under driven crank pulley. 

[ChrisC]

Thankfully 8500rpm is a little beyond a 420R.

 

[7 wonders of the world]

untill you upgrade her.....  

[ChrisC]

Since they stopped fitting R400 ARP bolts, based on the parts picking list on my kit, which includes the engine and chassis build up parts, I think I will pass. 

[Richard_420R]

@Tommyp, it is pretty easy to tell if the fan is kicking in - just idle it and as you say the temp will rise to a bit over 100 then you'll hear the fan start and the temperature will start to fall.  I have a new 420R too and was a little alarmed how hot it runs and that it can't seem to cool itself unless moving fast ... but I think it is all normal! 

[CtrMint]

Thought I'd add my experience here from my 2018/19 420R.

My kit initially had dodgy wiring at the rear of the fuse box,  I only spotted it after removing the fuse box.  The fan was confirmed as not working by removing the temp sensor connector from the block on the driver side, just before the manifold.  Disconnect that and the fan should kick in immediately.  If you do this I understand it's better when the car is warm as it will run rough when cold. Obviously be careful of your hands near the exhaust.

My experience of my car while driving has been as follows;

At "normal" speed it maintains temps around 90c, certainly below 100c.  In very slow/stationary traffic, after a long run the temps will creep up to 105c and the fan will kick in, which you can hear over the engine.  If stationary for any length I find if you give the car 10sec of an extra 1k rpm the pick in engine speed actually drops the temps below the 105c, and the fan cuts out. 

If I drive the car quickly over the Mountain Road, the temps lower a bit.  Weirdly at Kates Cottage they drop an extra 5c further, but the speed has usually increased quite a bit by that point.  By the time I reach The Creg, the temps are coming back up.  It must be something to do with the wind at that point increasing airflow.

Thanks

[ChrisC]

Mark, are you saying your 420R can't reduce its temperature at idle when the fan is running below the fan cut off temperature?

[aerobod - near CYYC]

The fan on the 420R should be capable of doing that. I have my R400D fan set to come on at 90C and off at 85C to minimise heat soak when idling in warm ambients. It will cycle on and off happily when the ambient is above 30C and the car is stationary and idling with the bonnet on.

[CtrMint]

I don't notice much of a decrease, it certainly doesn't get any higher.  That's said since I know I can trigger an immediate drop with the throttle, which I tend to do, I'm not waiting for it to drop with the fan.  It might just be me being impatient.  Plus, it's probably worth commenting there is only the lights in Onchan after coming off the Mountain where the car sits long enough, not a massive sample.  

[CtrMint]

This is exactly why I'm building a data logger for the car. Just can't find the time to finish it.  I'd have a complete detailed telemetry breakdown from every journey. 

[ChrisC]

So my new 420R build has the same radiator as yours, but can't IVA it at the moment due to the lockdown.  During my testing I have often let my car get to fan switch on temperature (with Easymap connected), but the fan brings the temperature down at a rapid rate, it only runs for 10 - 15 seconds before Easymap is reading 100C.  

Obviously I don't have the heat soak associated with some high load, and the ambient temperatures to deal with, but the fan / radiator combination seems more than powerful enough for the job, hence my question. 

I suspect you may have a problem somewhere, airlock maybe?

[7 wonders of the world]

the sudden drop after the application of throttle is due to the increase in pump speed.

 

[CtrMint]

I'm confident the car is fine, like I say the sample of what I'm doing is based on a lap round the TT circuit and then sat at one set of lights.  It's the only time I end up stopped in +33 miles of fun fast motoring.  I'll give it a test over the next few days as we are now limited to 40mph.  Usually it's had quite a bit more so good and warm. 

I've never seen a change in the coolant since bleeding either. If there was an airlock I'd expect some movement even minor.