Engine Radiator Coolant Level & Temperature


I would like to make a sensor that detects the following: 1. The level of the coolant in a diesel engine radiator. 2. The temperature of the coolant. 3. If the cap is screwed on correctly. (i.e it's on)

Has anyone any advice please. The coolant is usually an off the shelf bottle mix of anti-freeze at 30% that gets watered down during the summer and refilled towards winter. I do not know how toxic or caustic it is, as to whether it will eat probes etc?

Thanks, appreciate the help.

Kind regards,

jB 8)

Has anyone any advice please.

Making a sensor is not generally a do-it-yourself project.

  1. The level of the coolant in a diesel engine radiator.

There should be enough to cause the overflow tank level to move up and down. Much easier to put a float type sensor there.

  1. The temperature of the coolant.

Buy a commercially available sensor.

  1. If the cap is screwed on correctly. (i.e it's on)

No way to detect crossthreaded installation that I know of. If all you want to know is whether it there, or not, a simple switch that is pressed when the cap is on should be sufficient.

I do not know how toxic or caustic it is

Spill some, and see what happens to animals that drink it. You'll know.

There are sensors that can stand up to the mixture, though.

Temperature and pressure sensors might do everything needed.

They do need to fit in so as not to drop the pressure. On a diesel (commercial, truck) I am pretty sure those sensors are already there -- at least on modern engines.

Some GMs have a built in float switch in the radiator, you could get a bung welded in yours to thread one in.

Coolant temp is easy, many standalone PCMs use GM coolant temp sensors (the resistance vs temp curve is pretty well known).

And for the radiator cap. The radiator should build pressure if the cap is on correctly, and it won't otherwise. Put a pressure transducer in the radiator and see when it builds pressure in the motor (it may be soley by so many seconds after startup, by a certain temp, etc) and go from there. You could also easily detect a head gasket (or similar) failure by monitoring this.

Certainly your engine has a temperature gauge.

Don't know about diesel engines, but my Jeep has an overflow reservoir that partially fills with coolant after the engine turns off. That might be lots easier to measure the level in. When you open the hood when the engine is cold, and see no coolant in the reservoir, time to add some.

From what I've read, dogs like to drink antifreeze, but then they die.

britesc: 1. The level of the coolant in a diesel engine radiator.

How to do this depends entirely on the design of the cooling circuit. On some systems it will be hard to find a location where the level changes with fluid volume but does not change with temperature and pressure.

britesc: 2. The temperature of the coolant.

You need to use a thermister. They're cheap and readily available; your cooling system almost certainly has one already and probably has two. The bad news - if they're already being used for something else you can't sensibly share them and you'll need to add yet another one for your new system.

britesc: 3. If the cap is screwed on correctly. (i.e it's on)

If the system holds pressure, everything is OK. If it doesn't hold (enough) pressure, there's a problem such as a leaky hose or cap. Monitoring the pressure is far more useful than just monitoring the physical presence of the cap. However, you need to allow for the fact that the pressure will only build up as the temperature builds up, and if somebody is foolish enough to release the pressure while the system is hot it can take a long time for the pressure to come back up.

I want to do a similar thing.

This is my first Arduino project. I know very little, so will have lots of questions.

A sensor in the overflow tank is useless to me, I need to know if the liquid in the cooling system itself drops. This could happen if a hose or welch plug blows, or if something punctured the radiator.

Here's the sensor I thought I'd use ![](http://i.ebayimg.com/00/s/OTAwWDE2MDA=/$(KGrHqJ,!jIE6Io7E2HWBOjDpIsC4w~~60_12.JPG) eBay VW GOLF MK1 / MK2 COOLANT LEVEL SENSOR My car isn't a VW, I just think their sensor looks ideal.

and here's the fitting I plan to use to mount the probe into the top radiator hose (sorry about the size of this image, it's hosted on eBay) eBay Water Temp Joint Pipe

My plan was to run a small AC current from a pwn output on the Arduino to the probes, and set it to trigger a buzzer if the circuit is broken. The reason for using AC is to minimise the risk of electrolysis in the engine.

Is this feasible?

I also want to use the Arduino to manage a temp gauge in our automatic transmission. This will be project #2, with others to follow.