engine cooling

[TedTaylor]

There are some Alloy Water Temp Gauge Radiator Hose Sensor Adaptor being sold on ebay at the moment - aluminium with a threaded hole for the sender. Come in sizes from 32mm to 40mm for £9.50 free p&p.

Item number 200758149866 - seems a stock item.

Ideally things like this should be fitted in the top hose or at the top of the cooling system. This runs the hottest and would be most sensitive to high temperatures.

Ted

[James]

My pi never reaches halfway either, usually sits at 1/3rd to just below halfway, the estate used to always sit at nearly 2/3rds until I changed the stat for one from CW. It now sits at just below halfway. Both heaters get good and warm.
If I was you I wouldn't worry about the temp. reading, sounds just right to me.

And if you're really worried then get an IR thermometer from eBay — they're inexpensive and you'll be surprised at the uses for them.

[iggy]

thanks for the info guys ive also got what looks like a 3/8 bsp tapping plugged off on the rear left hand side of the cylinder head.

[CAR]

And if you're really worried then get an IR thermometer from eBay — they're inexpensive and you'll be surprised at the uses for them.

Yep have to agree with that James, I have one too, very useful.

[Clifford Pope]

It's important to remember the mechanism for engine heat control, and to be clear what does what.

Engine temperature is controlled by the thermostat. It stays closed until the water in the block is hot enough, then the thermostat opens progressively to let surplus hot water circulate through the radiator, to replaced by cold.

The cooling fan, of whatever kind, does not contol engine temperature. It's function is to help the radiator to dump surplus heat that has been passed to it by the thermostat. As long as the fan is powerful enough to shed heat in the most arduous circumstances, eg pulling hard up hill in blistering temperatures, or stuck in a traffic jamb on a hot day, then it doesn't matter what temperature it cuts in at as long as it is early enough to take heat away to stop the engine overheating.
That is how a traditional fixed engine driven fan works - it cuts in the instant you start the engine.

The point of an electric fan is that it provides a convenient way of turning off the fan when it is not needed to dump heat - ie it improves efficiency. To do so it is important that it responds to radiator temperature - not engine temperature. Setting the fan thermostat in relation to engine temperature is to fundamentally misunderstand the basic point - the thermostat controls ENGINE temperature, the fan controls RADIATOR temperature.

[Alec]

Hello Cliff,

very well put, a clear understanding of something's function goes a long way to solving any problem.

With regard ti infra red thermometers, they are very handy but my experience with the one I have (Maplin, but not a particularly cheap one) is the reading depends a lot on the type pf material it is aimed at. Probably more useful as a comparator rather than accurate readings.

Alec

[James]

Thanks for putting it so eloquently.

I've been trying to work out what the best strategy is for cooling — I presume what you'd want is for a fan to turn on when the outlet of the rad is the same as the thermostat?

[CAR]

Thanks for putting it so eloquently.

I've been trying to work out what the best strategy is for cooling — I presume what you'd want is for a fan to turn on when the outlet of the rad is the same as the thermostat?

So once you had reached a pre determined temp. on the radiator inlet and the outlet of the radiator was no cooler, ie the radiator was not having any effect on the coolant temperature. I think this is what you are saying anyway James.

Modern cooling systems,(without a/c equipment) seem to work on the basis of a preset temp switch just at the top or near the top of the radiator, with the coolant coming to this point direct from the thermostat. They also have very high efficiency in comparison to our older car systems.
If the 'stat opens at 82degrees, would a 10degree higher switch not work well because if the coolant temp is still increasing then that would indicate the engine was under more load or you were stationary (or you had a leak or other system malady) and would like the fan's assistance in maintaining heat dissipation.

Does anyone know what temps the stat and fan switches are rated at on modern cars?

Colin.

[David Withers]

Don't forget that the '82' marked on the thermostat is only the start-to-open temperature. It won't be fully open until about 95 degrees, which I think is still a little below the ideal operating temperature.

[Mike Stevens]

To add to David's post, as the 'stat has a range of 82 - 95 degrees with it being 'just' closed at 82 and fully open at 95, at any temperature in between these values, the 'stat is partially open. In this state, the flow of water to the radiator is restricted and therefore the cooling is also restricted from it's maximum cooling capacity.

This is actually all great as the 'stat then will control the water flow through the radiator such that the heat output and cooling required is in balance. If more heat is generated, the water temperature rises, the 'stat opens a bit more and so more cooling is available.

If the 'stat reaches it's fully open position, the heat being generated is now more than can be cooled by the radiator so overheating is likely (ignoring other factors for now). In normal running, you'd expect the temperature to sit somewhere between the 'just' shut and the fully open 'stat temperature.

With no engine fan, I guess it's more likely that the temperature will reach/exceed the 'stat fully open point, but in any case, it would seem sensible to me to set the electric fan turn-on point at or just above the 'stat fully open point. This should mean that the fan shouldn't come on very often and then only when really needed!

One useful thing to try is the old test of a 'stat in a saucepan of water on the cooker. Make sure you can see the 'stat valve OK and monitor the water temperature as it goes up - I use Ann's jam making thermometer when she's not watching. This should not only tell you the 'just' opening point, but also the fully open point.

Just my 2p worth on this wet and windy day.

Ah, yes, and Happy New Year to you all!

Cheers,
Mike.