Coolant temperature

[Chris Edgar]

I fitted a thermostatically controlled fan (Accuspark) a couple of days ago...
The temp sensor is in the top hose, as is the sensor for my temperature gauge.

Going by the temp. gauge I had fitted in the dash, I had problems getting the correct setting, engine was very hot by the time fan cuts in, so I checked the water temp in the top of the radiator with a "proper" glass/alcohol thermometer & found that the temp. gauge (TIM) reads 18 degC low

Armed with this new knowledge I have set the fan to cut in at just over 80 & all seems to work well.
I have also fiited an LED on the dash to show when the fan is running.

I'd be grateful for any opinions on just what the "ideal" running temp is..if there is such a thing!

[rayofleamington]

to be honest i'd say you only need a fan to cut in when the coolant leaving the radiator is hot - not when the coolant entering the rad is hot.
On modern cars, the fan cut-in switch is closer to the radiator exit than the entry.

The thermostat is there to stop water flowing to the radiator unless it is hot.
The radiator will cool the water and return it (cooled) to the engine (assuming it works properly - ie not clogged / blocked / silted up etc..))
The radiator heat energy loss works best when you're moving faster, which is fine for driving fast & working the engine hard.
When slow / stationary ( if/when the radiator isn't giving enough cooling) the water leaving the rad is hot - and this is when a fan will assist.

In traffic at idle is when the cooling energy of the radiator is low - and on a hot day the water returns to the engine still hot.
On a hot day, the air underbonnet air will be much hotter so the engine has less cooling to air.
As a tripple whammy, at idle the water flow is lower. When flowing through the engine slower it gets even hotter.

[IslipMinor]

Chris,

We have an electric fan and the switch is in the radiator header tank. It is not adjustable, but from the temperature gauge it cuts in around 85/90°C, which suits the thermostat that is 82°C. There is no point in setting the fan switch to less than the thermostat opening temperature.

In use the only time that it cuts in is in traffic, or after switching the engine off when parked.

[bmcecosse]

As with the others - it would be much better in the return pipe. But if kept in the feed pipe - I would set it to 90 maybe even 95 C . Your temp gauge may be right enough - by the time you measure in the rad it will have mixed/cooled with water already in the rad. Any idea what stat is in the head?

[Chris Edgar]

On modern cars, the fan cut-in switch is closer to the radiator exit than the entry.

That's interesting & I can see the logic behind that position, Ray.

Richard,

In use the only time that it cuts in is in traffic, or after switching the engine off when parked.

This is what I am finding too.

When the fan switches on it rapidly drops the temperature. It is a 9" fan, BTW.

The rad is only 3 or 4 months old. I had to replace when the old one was damaged by a flying stone on the M-way.

Roy,

Any idea what stat is in the head?

No, I don't know, never having had the cover off yet.

Many thanks for your input...I'll wait & see if there is any noticable improvement in fuel consumption!...or is it insignificant.
I will leave it in the top hose for now & no doubt at some future time I will have the rad out for some reason & I may put in in the return hose, as suggested

Chris

[bmcecosse]

I can confirm the fuel saving is insignificant......I run my Trav without fan - or electric fan...... I just switch off if I am stopped.

[Chris Edgar]

My dreams lie in pieces!

I can confirm the fuel saving is insignificant

.

No way I could run with no fan in the Lancaster traffic...back around 1971 I tried no fan on my Moggie as suggested in one of the magazines of the day...on the way to work, on top of a very long & steep hill, I had to get it out of the boot & put it back on ...never tried again after that

[hanvyj]

I have just installed this exact same setup on my car! I set it to mid 80s but might turn it up a bit because it comes on when moving sometimes.

I was told the water goes into the engine through the top hose? Hence the thermostat being there.

Out of interest, did you take the fan power off the solenoid? Usually my fan comes on when parked and I was wondering if this is a good idea. Obviously it doesn't stay on long.

[mike.perry]

I can confirm the fuel saving is insignificant......I run my Trav without fan - or electric fan...... I just switch off if I am stopped.

The trouble with that is the engine keeps heating up when it is switched off and there is no water pump to circulate the water.
I ran my Series MM through one summer with thermo syphon cooling and no fan, just a temp gauge. It got close to boiling but not quite.

[JOWETTJAVELIN]

Normal running temperature is 70-75 deg. C.

[IslipMinor]

I would suggest a 'permanently' on fused supply to the fan, as that way if there is a build up when the engine is turned off, the fan will help to cool it down. Our 1380 usually runs around 170/175°F, but when switched off the temperature in the head climbs up to ~190°F, when the fan cuts in, and then is cooled back down.

In its modified 948 days, we ran with no fan, but lived in a small town with very little stationary traffic, so never had a problem, but I would not like to run the 1380 in much more mixed conditions without one.

[Chris Edgar]

Yes, I have it on permanent..connected to starter switch & fused at 15 amps (fan is 80 watts)

[Chris Edgar]

I was told the water goes into the engine through the top hose? Hence the thermostat being there.

Water goes out of engine into rad via top hose