False Coolant Idiot Light

PDLarson · Post by **PDLarson** » 17 Jul 2013, 14:16

Can someone check their coolant expansion tank and tell me if your level sensor inside the tank floats and bobs back up if you press it down below the water?

I'm trying to understanding the function of the coolant level sensor. I have a false coolant indication on the dash and noticed the round thing in the tank looks to be sunk or stuck at the bottom. Is this normal?

Backstory: I replaced the engine coolant temp sensor and thermostat and decided in my less than infinite wisdom, rather than risk breaking a petcock, or crawling under the block, I'll just move the coolant expansion tank to behind the engine (and therefore below the level of the t-stat. This actually worked well as I only lost not much coolant. Yes I know I could have drained it all and many would say I should put in new coolant but guess what, it is new coolant so no, I don't really want to loose much or replace it.

Anyhow, after having that coolant expansion tank upside down and every which way, now I have a coolant light that won't go out. I have checked that I did in fact reconnect the sensor so yes, that is plugged in. The wires look ok but I have not done any electrical testing. But I do see that the "float" doesn't seem to be floating. However I'm not sure if that is how it works or if it somehow measures specific gravity (I just needed to add a little bit so I just used water), is it just supposed to have air under it which I messed up when inverting it, I have no idea.

Ideas? Thanks!

Post by **rspi** » 17 Jul 2013, 14:51

It's a cork, it is suppose to float. Poke it with something and see if it frees.

PDLarson · Post by **PDLarson** » 17 Jul 2013, 15:14

No, it stays under water. I'll have to see if I can grab it with something to try to lift it up. So far at work with limited tools I've only been able to poke at it with a screwdriver but can't lift it.

Thanks for letting me know its cork though.

If I remember right you're in Arkansas. I may be in Russellville sometime in the next few months to help my Dad move. Maybe we'll cross paths. Like, I'm from MT, hey I know someone from MT, do you know them? Sure. I've met everyone in MT, funny! Well I'll keep my eyes peeled for an awesome wagon when I'm there

Post by **Ozark Lee** » 17 Jul 2013, 19:23

Take the heel of your hand and give the tank a good smack on the side. That will often free a stuck float. The bad news is that it will more than likely get stuck again. If they get stuck once they tend to keep sticking for some reason.

...Lee

Post by **rspi** » 17 Jul 2013, 19:38

Where is MT? My wagon is black. Here is a pic.

Post by **rspi** » 17 Jul 2013, 19:40

I have a good coolant tank if you need it. It has a little sediment in it that I could not clean out but it works fine. Just PM me your address and I'll ship it to you.

PDLarson · Post by **PDLarson** » 17 Jul 2013, 23:08

Very nice wagon. I especially like the color of the wheels

You'll see why in the pic of my ride (but not the pic in my sig). Sorry about the MT confusion, that's MT as in Montana USA. It is the fourth largest state, way up north, borders Canada, and cold in the winter, especially for a transplant from SoCal like me.

Thanks for the offer of the tank. I hopefully will not need it. I pulled mine and discovered that I think the sensor that goes up into the tank from underneath to read the float position is bad. I'll stop by a local JY tomorrow that has one and see if I can just swap sensors. It snaps right off of the bottom of the tank. I must have messed up the wires (as in pulled too hard and maybe moved something inside the sensor that shouldn't have moved) when I was first trying to figure out how to move the tank. Mine is a '99 with a rectangular tank (as viewed from above) and the power steering fluid reservoir is mounted to the side of the coolant tank. Anyway, I took some measurements and found my sending unit would give an open or closed circuit. The funny part is that it is reversed. If the float is floating, I have a light on but if I force the float all the way down and hold it, the light goes out. I'm confident it is just a bad sending unit but I'll try to confirm tomorrow. I checked the float and it does move freely and it does toggle the sensor to switch from an open to a closed circuit.

My ride

The part, 9445317

Post by **abscate** » 18 Jul 2013, 03:05

must have messed up the wires (as in pulled too hard and maybe moved something inside the sensor that shouldn't have moved) when I was first trying to figure out how to move the tank

Exactly what I did. Replacement thread here...

https://www.matthewsvolvosite.com/forums ... el#p292579

I did 5 years in Big Sky Country...Go Cats!!!

SoCal to MT...talk about culture shock....

PDLarson · Post by **PDLarson** » 18 Jul 2013, 12:18

Thanks for the input everyone. I just returned from the local pick a part. Picked up the coolant sensor, two sidemarker lights (just as a backup for when the little plastic clips fail on mine) and a light bulb for another car for $5!

Did the part swap in the parking lot and my problem is solved. Thanks again for the input. I'll post a link to this thread in the other one since this one gives a pretty good description of what was going on that led up to needing this repair and some background on how the sensor works electrically.

Basically I found the tank has a cylinder that the sensor goes up into from below. Inside the tank, there is a donut shaped white piece that floats and goes up and down around this cylinder. There should be a black rubber cap over the top of this cylinder to keep the donut float from floating away from the sensor. Apparently the wires can be pulled partially our of the sensor when messing with the tank, causing this false coolant light. The sensor simply switches the circuit from open to closed, triggering the light, in this case at the wrong time. In fact, I found that if I held the float down, the light would go out!

My part number was 9445317 and my replacement from a nearly identical V70XC same year was a different part number but worked perfectly. I think there are several interchangeable part numbers as the article linked above shows yet another P/N.

Post by **mikealder** » 18 Jul 2013, 13:53

A quick fix for the stuck float issue is to remove the tank and fill it with fresh water, pop a couple of sterident tablets in to it (false teeth sterilising tablets from a local pharmacy) and put the cap back on, leave it for 20 mins then flush it out.
Inside of the tank will now be cleaner than it was so refit to the car and top up with coolant - Mike