Adding a Coolant Level Sensor!!

[MadeInJapan]

I'm sorry- no write-up yet, but I'm going to be working on this- it's a new project of mine.
Why???

Well, because our cars don't have a sensor in the expansion tank (reservoir) to tell you when your coolant is low. This is a huge Volvo over-sight, or is it? Is it just another way to make more money from us??? This should be the first defense against loosing your coolant and overheating and rendering your Volvo as pretty much toast!! Ask the many members on the different forums whose lower radiator hoses broke and immediately shot their engine temps through the ceiling, toasting their aluminum engines. I had a close call yesterday. it wasn't a hose but after getting to work, I looked out my window and saw coolant all over the ground under my car. My expansion tank had cracked and spewed my coolant out. Fortunately for me, that was the extent of my loss! I got some fluid from the local auto parts store and although I looked for a replacement reservoir, I could not find any from our local parts stores so went to the dealer for full retail price. Still, better than a blown engine.

So, I wonder, why is there a windshield washer fluid level sensor but not one for the coolant?
I'm working on a, I hope easy solution, to add a level sensor to our expansion tanks, tie into the wires from the window washer tank so that you will get a warning on your dash if either of these tanks are low. When the message comes up on your dash, at least this way, you know to get out and check your coolant level.

I'll keep you posted in regards to this. In the meantime, if anyone here has any ideas on this, please let me know. As things are progressing, I'm thinking that this is going to require a placement of a float in the reservoir, hopefully from the top with a locking washer on top so the tank will still hold pressure.

-MIJ

[oragex]

Interesting. The S60/V70 does have the sensor. I agree, it is extremely important, engine temp gauge is not enough.
Perhaps a S60/V70 expansion tank fits in the S40?

[MadeInJapan]

Unfortunately, they are not the same.

Here is the one for our P1 models:


Here is the one for the S60/V70's:


The other issue is going to be to add the line from the sensor to something that can be read on the dash. I'm still thinking that tying into the washer fluid level sensor is a good way to do this- When the washer level is low then it's time to stop the car and check the coolant level as well!! I believe that as long as the circuit stays closed (washer fluid or coolant is touching each probe) the warning is off but when one of the circuits is open (washer fluid or coolant does not touch both of the probes in one of the tanks) then the warning will come on! This to me seems like the simplest solution...now to find a compatible probe that can sit from the top of the tank and screw down to form a seal (much like the water line works going into a toilet tank from below) and be short enough as the tank is not that tall...

[MadeInJapan]

The coolant reservoir is separated into chambers inside which are then all connect. This limits the amount of room there is to install anything extra. And, although I wanted to place a vertical float in it from the top, all the float switches that I found in that configuration are extremely short (1 ~ 1/1/2 inches) which I'm afraid will activate with an ever so slight drop in the coolant- something we don't want. A Horizontally placed sensor therefore appears to be the best option after all. The question is if a stem length of nearly 3 inches is too long for the middle chamber- the only section of the reservoir that can be reached from outside, through the cap hole- something you'll have to be able to do if you are going to insert and place the float into the reservoir. Here is the part I'm thinking of using at the moment.


Any comments are most appreciated!!

[MadeInJapan]

I found that the above sensor is too long to fit into the reservoir tank as the tank is compartmentalized and there is only about 2 inches of clearance across each section. So, instead I just purchased a vertical float sensor from Amazon which I'm hoping will work. I will post back after it comes and I've had time to experiment. I believe I can squeeze this through the opening in the top of the tank and install it in the bottom of the tank with a locking nut that was less than a dollar sold as an "add on." I'm not sure if the unit comes with a rubber gasket, but if it doesn't I don't think I'll have much trouble sourcing one locally. Anyway, here is a picture of the float:

[MadeInJapan]

So, my float switch came today...specs on it are that it can withstand the temps as well as the corrosive properties of the coolant. So that's a good thing. The other thing is price is right...it and the tightening nut together were about $10.
Length also looks good. And, the whole thing will fit through the cap opening and I can install it in the first compartment of the reservoir which I can get my fingers into or at least a long needle nose to hold it in order to tighten it. I looked through my box of 0-rings and also found one that would fit- these are actually o-rings for injectors so they should be able to withstand some coolant- they can withstand high temps and gasoline already. So, there are several ways I can install this. At this point, I'm just trying to get a visual using my reservoir that was cracked and removed from my car (the one I will experiment with first) before doing any surgery to the new tank reservoir currently in my car.

1. Looking from the bottom of the reservoir (with the tank flipped), I can install from the bottom of the tank... with the switch turned the right way, the float would signal me if the reservoir is emptied:

2. At the top of the tank, inserted right in front of the filler cap, the sensor would signal me if the coolant dropped to below the seam (where the full fill line is)...this seems more prudent but I have not actually tested it yet.

Another look at option 2 to give perspective as to how much room is actually available in that section of the tank.

Comments are welcome!!

-MIJ

[MadeInJapan]

Update- I had a chance to play with the cracked reservoir tank and the float switch. I tried first to install it in the top of the tank and then filled the tank (rubber glove rubber banded to the large opening at the bottom where the lower coolant hose attaches). Unfortunately, a signal would be set even before the coolant level hit the "max" fill line so that location is out. I next tried the bottom of the tank. This seems to be a viable solution although in the car, that section of the tank sits right above the A/C condenser hose and it will be a tight fit. I will most likely have to cut the coupler used to screw onto the threaded stem of the float switch to make is shorter for things to fit comfortably.

View of the float switch attached to the bottom of the tank:

Level of water in the tank where the alarm will be set (closed circuit):

The larger black hose in this picture is what will be sitting directly under the wires that come out of the reservoir tank most likely necessitating me cutting the PVC coupling used to hold the float switch snugly in the tank.

I have the water still in the tank with the tank sitting in the sink over night on dry paper towels to make sure there is no leak before I decide to install the float switch in my actual reservoir tank in my S40.

I am also thinking about tying into the engine temp sensor rather than the windshield washer level. This way there is much more dramatic of an alert- a Red Triangle on the dash as well as a message in the message center. Otherwise, I could also install a piezo alarm which would just make all kinds of racket to alert me. Not sure which yet. Any ideas on this would be welcome!

-MIJ

[MadeInJapan]

I know that no one seems to be reading or following this but at this point, I'm moving on trying to find a good qualify piezo buzzer/alarm for cheap. I'm either looking at tying it into the car's power or possibly just using a little battery box separate from the car's system. If/when it goes off it will be really obnoxious, so I also need to install a cut-off switch.

Once I get everything done, I'll post a "How to" in the Repair Data Section.

I really would not want to drive one of these cars without some type of early warning when the coolant evacuates the system!

[kcodyjr]

Why did you abandon tying into the engine temp sensor? I'd much rather cause a dash warning than have to support a piezo, especially with batteries.

[MadeInJapan]

I have not bought a piezo yet... still open to suggestions here. I got sidetracked with a sailboat I'm working on and an injury. How would you tie into that sensor?