Coolant Level Sensor

[james_s]

Uh it's a float-based system, moving parts and yuck I don't like reed switches getting temperature cycled. And it's $228 OUCH. A model T could use a float sensor.
Capacitive level sensing is superior - no moving parts, nothing in contact with the fluid. But it needs more sophisticated electronics and firmware.

Capacitive sensing may be superior, but millions of cars on the road have float based liquid level sensors for various fluids, they work fine.

[static333]

To me, an overflow bottle sensor would be useless. I have a 1993 Mazda B2200 pickup. A packrat chew through a small water hose, supplying the intake manifold. Drove off and overheated. Collant level in the overflow bottle was normal as my system is not pressurized. Temperature gauge indicated only a slight temp. rise. Now I am checking the coolant level in my radiator each time before driving off. Looking into placing a temp sensor or a radiator-fan switch directly on the cylinder head, not into the coolant.

[floobydust]

I'm not sure what definition of "modern" you're using but I have a 40 year old car that has the coolant reservoir pressurized. I'm not sure how you'd have it any other way unless you had a checkvalve, the plastic bottle connects directly to the radiator via a length of rubber hose so the pressure in it is the same as in the rest of the cooling system.

The check valve is the radiator cap, it seals against 7-14PSI but not against vacuum.
I think the change came with plastics being able to withstand say 21PSI, or maybe it was safety.
Classic Chevy from the 1960's coolant recovery bottle was an option, more like an expansion tank connected to the radiator cap pressure relief port. It was for farm trucks that would overheat and people didn't want to lose glycol. See Model T erupt like a geyser when they overheat.
Otherwise, the radiator cap pressure relief port hose drained onto the ground, no recovery bottle at all until around 1972 it became standard equipment. It might also be due to cross-flow radiators (no tanks on top), vehicle emissions control causing engines to run hotter, in the 70's.
Safety issue is if glycol gets on the windshield, it just smears with the windshield wipers and you can't see much of the road if it boils over in a messy way.
Lots of Toyota's under 40 years old have coolant recovery units, but unpressurized. It seems to vary with car manufacturer's mindset.

Capacitive sensing may be superior, but millions of cars on the road have float based liquid level sensors for various fluids, they work fine.

Not according to the many Youtube videos, and most float sensors are embedded in the tank - non-servicable. A moving part in hot glycol mix with vibration and sloshing, add some dirt and oil - and it looks like all sensors are problematic. New vehicles are using capacitive probes, non-contacting with the fluid, no need for a cable-gland to run wires out of a pressurized compartment. Dodge RAM uses a reed switch inside a pressure well, with a float+magnet.
The sensors using electrodes seem to not work well either, Audi/Volkwagen expensive to change the tank. The probe resistance seems to be poorly engineered and of course the whole assembly has to be replaced, even if you only had a dirty electrode.

[Mechatrommer]

To me, an overflow bottle sensor would be useless. I have a 1993 Mazda B2200 pickup. A packrat chew through a small water hose, supplying the intake manifold. Drove off and overheated. Collant level in the overflow bottle was normal as my system is not pressurized. Temperature gauge indicated only a slight temp. rise. Now I am checking the coolant level in my radiator each time before driving off. Looking into placing a temp sensor or a radiator-fan switch directly on the cylinder head, not into the coolant.

its time to do major check... water pump dead? coolant leaking somewhere? indicated by level drop in radiator? find the leak! pray its not into cylinder block. if it is, major overhaul, fun! i never heard a car that will tell you "mr! you need to change top gasket! your water pump is busted! mr! i'm leaking badly!" the best i encountered so far is alphard 2018 model which will tell you to break for coffee if you drive more than X hours straight. which i think pretty stupid (i know when to take a break)

[darkspr1te]

I few idea's here.
In my old landrover i used a ULM2003/8 to create a led based water level sensor, the device uses the liquid to act as a switch on the ulm2003 and will trigger the ground side based on level of water.
The other trick i have used is a ultrasonic send/rec pair inside a tube, the tube stops the liquid from moving too much from the sensors location , that device was sold by a Ukrainian company called Escorts  or Digital Escort.

There also capacitive fluid sensors which should also work.

darkspr1te

[Circlotron]

Maybe a useful addition would be a water pressure sensor. Once the system is hot a burst hose would drop the pressure from several psi to zero very quickly, even before all the water has been lost and temp starts to rise. It would need to be disabled until the temp (and consequent pressure) initially rose to a certain minimum value.

[floobydust]

Low coolant sensing is still required for solar and electric car/battery banks. It seems to be all about price-point," here engineer you've got $1 to come up with something".
Tesla low coolant sensor is a lowly float/reed switch. Powerpack uses the same coolant recovery bottle/sensor as the cars. But no vibration in the Powerpack.

Interesting to note coolant contains about 5% corrosion inhibitors, defoamers, and along with the rubber, lime, calcium, metal dust, oil - this might clog a float/cover electrodes.

Pressure doesn't say much about low coolant level - where does the pressure come from anyhow? It's worth pondering... It only jumps up when it boils over.

[james_s]

Ordinary water/glycol cooling systems are pressurized, they run at somewhat higher than atmospheric pressure at normal operating temperature, it is done to increase the boiling point of the coolant. I agree though that monitoring pressure is not very useful, the simplest way to get the earliest warning is to monitor the level in the expansion reservoir. This way whether the leak is slow or catastrophic, you will be warned at the earliest possible point, when the reservoir is low but the engine is still filled with coolant. Float sensor with a magnet and reed switch or hall sensor will work. Optical sensor with LED and phototransistor is an option. Capacitive could work, maybe ultrasonic, even bare electrodes may be workable. It all depends on budget and mechanical constraints.

[BrokenYugo]

If it has an unpressurized reservoir, there are failure modes you won't catch looking at it, like a bad radiator cap (dirt common failure) or overflow hose, or a hose blowout if you miss the giant steam cloud.


If you're looking for max reliability, make an inspection checklist and pop the hood often, treat it like an aircraft.

[SmallCog]

even bare electrodes may be workable.

Another product here in Australia from quite a reputable manufacturer uses electrodes.

They make a point of the sensing being AC to prevent corrosion

https://www.redarc.com.au/images/uploaded/FLYER6-4%20-%207263%20LCA1224%20Coolant%20alarm%20ANZ%20brochure%20220128%20LR.pdf

Before choosing to monitor the tank it's essential to understand how the system functions. There are current model vehicles here in the carpark at work that have the traditional unpressurised overflow bottle. The level of these bottles (probably) wont change if you have a fault as they rely on a vacuum being created as the cooling system cools down to draw the fluid in.

[Circlotron]

Before choosing to monitor the tank it's essential to understand how the system functions. There are current model vehicles here in the carpark at work that have the traditional unpressurised overflow bottle. The level of these bottles (probably) wont change if you have a fault as they rely on a vacuum being created as the cooling system cools down to draw the fluid in.

Good example is son's '98 Camry that has plastic top and bottom radiator tanks. The top tank developed a small crack next to an integral mounting bracket and as a result it did not draw coolant in from the expansion tank because of the air leak. The overflow tank level looked normal but the radiator was way down.

[Pjf]

Gday, been busy the last couple of days, have some pieces on order, will update you guys once they arrive and I test some things out.

To many of the detractors who keep saying that this wont work because of it being an overflow tank, the car I'm installing it on doesn't have an overflow tank, it has a pressurized header tank, that is an integrated part of the cooling system(see attached picture.)


I've spent enough money on this car recently that a simple diy coolant alarm is quite frankly cheap insurance, considering last time I lost coolant, temp gauges showed nothing at all, it was only when I started to smell coolant after winding down a window that I noticed something up, by then it was too late, when this happened I had factory and aftermarket temp gauges, both of those didn't read any different until AFTER I pulled over. Now I've got the factory temp gauge, aftermarket temp gauge, engine watchdog and I'll have this alarm as well, once this is installed, it won't be obvious, it will be invisible until it goes off.

for those not in the know an engine watchdog monitors block or head temp directly with a bolt on thermocouple.

[SmallCog]

Gday, been busy the last couple of days, have some pieces on order, will update you guys once they arrive and I test some things out.

To many of the detractors who keep saying that this wont work because of it being an overflow tank, the car I'm installing it on doesn't have an overflow tank, it has a pressurized header tank, that is an integrated part of the cooling system(see attached picture.)
(Attachment Link)

I've spent enough money on this car recently that a simple diy coolant alarm is quite frankly cheap insurance, considering last time I lost coolant, temp gauges showed nothing at all, it was only when I started to smell coolant after winding down a window that I noticed something up, by then it was too late, when this happened I had factory and aftermarket temp gauges, both of those didn't read any different until AFTER I pulled over. Now I've got the factory temp gauge, aftermarket temp gauge, engine watchdog and I'll have this alarm as well, once this is installed, it won't be obvious, it will be invisible until it goes off.

for those not in the know an engine watchdog monitors block or head temp directly with a bolt on thermocouple.

You need one of these too, sounds like you're a collector! :-)

https://www.aisat.com.au/our-products/commercial/murphy-switch-gauge/murphy-20-series/murphy-basic-temperature-gauge/