Low Coolant Sensor Fix

[Brent S]

For all the people who have been experiencing their Low Coolant light coming on, even though the coolant's not low:
I took a wire hanger and put a 90 degree bend in it, about 2 inches from one end. I then took the radiator cap off, and stuck the end of the wire hanger into the radiator, so that the bent portion of the wire went into the port where the sensor is installed, and poked around a bit. I believe I was able to clear away the annoying, infamous "sludge" build-up from the sensor's electrode, which is a lot easier than removing the sensor.
I have been attempting to flush & clean the radiator (and sensor) for a year now, and this seems to be the easiest "fix". Apparently, this sensor design is poor, in so far as any small amount of debris tends to collect on the electrode and produce false low readings.
Enjoy!

[BNaylor]

Not a bad suggestion however. You're better off removing the sensor and cleaning it. See pic below. Unless you have xray vision I seriously doubt you got all the sludge buildup off. Therefore not a good long term fix or the low coolant warning light will come on again. The sensor is easy to access and remove just by removing the headlamp assembly.

[Brent S]

Yes, I'm sure the sludge will build-up again. However, I found it only took me 2 minutes for this "fix", as opposed to draining coolant and removing the sensor. I could easily do this every few weeks, if need be.

The picture comes across as only a red "X", for some reason. Do you know why?

[BNaylor]

Pic looks fine to me.

If sludge caused by air, oil or combustion by-products is causing the issue then you need to find the source of the problem. Didn't you have issues with oil in coolant?

You only lose about a half quart of coolant without draining any out of the radiator when you remove the sensor. Just undo the sensor clip retainer and pop sensor off the radiator. Just have a catch pan ready to get the old anti-freeze.

[tblake]

My old sensor was giving me a constant "low coolant" light also, even with the resivore full. I took it off, cleaned it up, put it back on, and it only worked for about a week. I have since just replaced it, and when I took the old one out, there was no build up on it at all. (weird) The new one has been working just fine since install.

Coincitently, my "low coolant" light issues with the original sensor first started happening immediatly after a coolant flush and fill with prestone dex-cool. Maybe the original sensor has compatibilty issues with prestone brand dex-cool? Anyone else notice this?

I have saved the old sensor and was going to do an expiriment by aquiring various types of coolant, submerging the sensor, and measuring the resistance across the sensor's terminals.

I just havn't had a chance yet. I wonder if % of coolant/water mix could also play a part in this issue???

[BNaylor]

Originally Posted by tblake

Coincitently, my "low coolant" light issues with the original sensor first started happening immediatly after a coolant flush and fill with prestone dex-cool. Maybe the original sensor has compatibilty issues with prestone brand dex-cool? Anyone else notice this?

Yup. That is the trend I see. I recall some of our members just gave up and disconnected the sensor. As you can see by my pics this GM car had Prestone Extended Life and it had a steady and flashing low coolant warning after switching over from GM brand Dex-cool. However, later on it turned out to be air in the radiator. Replacement of the sensor did not fix the issue. The radiator had a very small coolant leak at the seam of the radiator driver's side below the upper radiator hose fitting. Not even enough to accumulate sufficiently and drip on the ground. All I could surmise is air was being sucked in when the engine was off and during the cool down process. In this case replacement of the radiator resolved the issue.

However, every situation will probably be unique so hard to tell what any real fix will be unless you get lucky.

[Brent S]

Well, I thought I may have had oil leaking in.....but you thought it was likely to be sludge, and lately I've been thinking that you were right. The radiator cap is usually dirty after a week (or longer), but there doesn't seem to be any real increase in sludge, so I'll just continue to monitor, etc.
Thanks.