Eric Trujillo

So this has been happening for a bit. Every other day, I'll get in my car and I'll turn it on, and the low coolant light will come on. I've checked the reservoir, its full to where it needs to be, and the car never overheats. In fact I've checked it with my tuner that the fans are set to turn on at 200 degrees and the gauge never goes above the first line. So I'm thinking its a sensor issue. Does the coolant reservoir have a sensor? Maybe coolant temp sensor?

wssix99

iTrader: (5)

Yes. It's a coolant level sensor and it has a short life compared to many of the other sensors in the engine bay.

Shortly... you will see posters telling you to unplug it and ignore it. I highly recommend that you not do this and replace it properly. It saved my car from melting down and I can't say enough about how important it is.

The easy change is to siphon out enough coolant from the radiator (in to a jug or pail) until the sensor is well-exposed. (You can see it through the radiator cap opening. It's half-way down the side of the radiator.) Replace and then dump the coolant back in. The new one should cost you $30-40.

Once you have the old sensor out, you'll want to diagnose the issue. Sometimes they look clean and just go bad. Other times, they get contaminated from power steering cooler leaks or get corroded. If you have contamination, then that obviously needs to be addressed. If you have corrosion, this is likely a sign that your coolant is too old, has lost its rust inhibitors, and that its' time for a full flush and change.

^ The latter happened to me this summer. It came out all rusted, so I quickly turned around and did a full flush. (This is not easy to do, as half of the coolant is stored in the engine block.)

RPM WS6

iTrader: (3)

To add to wssix99's post above, I seem to recall folks complaining about the aftermarket level sensors not working so well, so probably best to get a new one from GM if you decide to replace it.

At least, in this case, it shouldn't be due to PS fluid contamination since a base '98 TA shouldn't have come with a factory PS cooler (RPO V12.) Probably just less-than-ideal coolant maintenance over many years has resulted in some gunk build up, etc.

wssix99

iTrader: (5)

I have some good data points on these. (Unfortunately.) I haven't seen the Delco's perform any better than aftermarket.

I've been through 5 AC Delco Coolant sensors and 1 Wells.

Of the 5 AC Delco's, 3 were trashed by a leaking PS Cooler. (The dealer fixed that under my initial warranty and they didn't figure out the problem until we hit the third...) The later two sensors had natural lives of 50K miles and then 30K miles.

My Wells sensor lasted 25K miles, but I had a lifetime warranty on it from AutoZone. (This sensor died from corrosion, so I don't fault Wells for that.)

I'm now on a Duralast, which replaced the Wells sensor - still on the lifetime warranty.


I will temper this bad news by saying that I haven't been as diligent on coolant changes as I should have been - but I was following GM guidelines. Either way - the basic design of the sensor (no matter who makes it) is not very durable and I HIGHLY recommend getting a replacement from a parts store that will offer a lifetime warranty. -> Pay for it once and then never again! (It WILL go bad again...)

Eric Trujillo

Well that explains some of it. I mean the car sat for 2 years with a busted fuel pump before I got it. I did a coolant flush about 20K miles ago but I didn't get any weird notes from my tech who did it. I'm assuming the interval is around 30k to change it right?

RPM WS6

iTrader: (3)

This is interesting, I recall a lot of complaints about the aftermarket versions at one point. I don't recall specific brands, just people installing them and seeing failure right away, then getting a GM version and having no more trouble. Perhaps there was a period when a bad batch of the aftermarket ones were in circulation?

I've never had one fail myself. But that's mostly because my '02 car didn't come with one from the factory, and that's the only 4th gen I ever put a ton of miles on. My other three have been garage queens treated to many more coolant changes than were ever necessary and limited overall usage.

Coolant flush is due every 5 years/150k miles, per the factory maintenance schedule, if you're still using Dexcool blended with only distilled water. But if you wait the full five years, you really should do a comprehensive/complete flush.

wssix99

iTrader: (5)

I'll bet your fresh coolant did the trick. All of my short-lived sensors were bathing in bad or old coolant. The longer ones were up against coolant flushes/changes.


It will be interesting to see what your old sensor ends up looking like. When mine came out all corroded, I educated myself on service tech "flushes" and how inadequate they are. A proper flush is hell and I can't imagine having to pay someone else to do it properly!