Low Coolant light, intermittent behavior?

Hey again, fellas.

Well, I've decided to stop ignoring this problem. My low coolant light comes on and off. Sometimes it's off for months, sometimes it goes on and it's like that for a week or more. Totally intermittent. The coolant level is fine. I've added some here and there, but I really don't think there's a leak.

I did a quick search, and I found in the Series I board that it was recommended that they bleed the air out of the coolant system using the brass bleeder screw on top of the thermostat housing.

Would it be the same advice for me, or is it possible that I could have a bad "Low Coolant" sensor? And there were some conflicting opinions on the procedure for bleeding the system - do it on a warm engine, or cold?

As usual, any help would be appreciated. If I get this kink worked out, I think my Riv will have all the bugs worked out (which will be a rare thing indeed).

Thanks!

I would bleed it and if that does not fix the gremlin then replace the sensor - after which you will have to bleed it again...

Albertj

Hey guys I'm new here.

Got a quick question. I'm looking at buying a 97 Riv supercharged with 90k on the O. It has a low coolant light...is this something to worry about? I read in a different post on this forum that it's either a coolant sensor, or air in the lines. I just want to make sure this can't be a sign of a cracked head. Thoughts?

Also is $3500 a good price for a relatively good condition riv? Mechanically (besides the coolant light) it seems to be good. The body only has a few small dings, and the car was definitely repainted. The paint does not look like the usual base coat clear coat type of paint. There is a good amount of overspray on the plastic exterior pieces which was a dead giveaway that this car was repainted. I ran an autocheck and it was clean with no accidents. There appears to be no bondo work or orange peel, and also all body lines are perfectly aligned. So I'm guessing the paint was just bad and the previous owner through a cheap paint job on it.

Knowing this does it seem like a decent buy?

Hey there!

Yeah the factory paint can really take a dump sometimes. Mine has also been resprayed.

If there is actually coolant in the reservoir , then it is probably just air in the lines or a sensor. Either way its an easy fix.

3500 sounds pretty good. I'd offer 3200 , or maybe even 3 and see if you could get it for less. FWIW I paid 4k for my 96 with 74k miles as year and a half ago , so that price doesn't seem too far off the mark.

If the accident was paid with cash by the owner, it wont show up on a carfax report. You should drive the car, for no less than an hour and a half straight. Make sure to get it up to normal operating temperature.

Look underneath it. It should be dirty, but with very little oily residue. If it's real oily, then there's a problem, if it's real clean, that means they're trying to hide something.

Ask for any maintenance records.

Going out on a limb and guessing something allowed the coolant go low in the first place. One very common problem with Series II 3800 engines is a leaking LIM gasket, which can let coolant escape through the exhaust or into the oil, or it can even seep out the sides of the manifold, I guess. It usually starts as a very small leak, so if it's gotten that bad you can easily tell in one of 3 ways:

-check around the engine for coolant dripping from the LIM gasket area, just under the blower.

-check the spark plugs. Coolant in the cylinders will create deposits on plugs. It looks like a white ashy build-up.

-you can take an oil sample and send to Blackstone Labs for analysis ($25). They'll tell you what's wrong. One of the biggest reasons they've found for coolant in the oil is a leaking LIM gasket. It's not very often the head gasket.

Even if you find the LIM gasket is leaking, there is a new aluminum replacement that solves the issue, available for $30 or less, and can be installed fairly easily (I need to do mine soon!). The car you are looking at would still be a nice deal if that's the only problem you can find. Best of luck.

My 2 cents:

From the way you've described the car, and with that low mileage, I think the price is right.

It took GM years just to get the Low Washer Fluid sensors to be reliable, and they also completely changed the Low Oil sensor in these engines during the run of the Riviera.

I'd also bet on a bad sensor because there is no way that "air in the lines" is going to affect it. It is almost uselessly mounted on the rear of the passenger side radiator tank, between the tranny cooler lines. It is mounted more than halfway down the radiator, so if it were really seeing air, you'd already be seeing some serious temperatures on the gauge...

I wouldn't just go by the overflow tank, however. Bad radiator caps can do funny things. Just check the actual radiator level with the engine cool. If it's full, then you're fine. While you're at it, you can point a flashlight down behind it and see if there is any problem with the wires on the back of the sensor. For all we know, the light goes on when the circuit is open, and one broken wire or corroded contact would turn it on.

light is off if the circuit is broken or the sensor is unplugged.

i've had air in my coolant system causing the light to come on before, usually right after a flush and fill. you are right the sensor is placed very low in relation to where air normally like to go (up). but the system is pressurized and the lower hose is right below the level sensor, so if there is air traveling through the system it surely has to pass the sensor on its way out of the motor.

and off topic, but did they make a revised version of the low oil level sensor?

Mr.Riviera wrote:

light is off if the circuit is broken or the sensor is unplugged.

i've had air in my coolant system causing the light to come on before, usually right after a flush and fill. you are right the sensor is placed very low in relation to where air normally like to go (up). but the system is pressurized and the lower hose is right below the level sensor, so if there is air traveling through the system it surely has to pass the sensor on its way out of the motor.

and off topic, but did they make a revised version of the low oil level sensor?

Thanks for the info about the circuit. I'm running blind since I recently joined the group because my memory sucks and the "service" on my computer (like Windows Messenger Service, etc.) won't start for my GM SPO eSI (Service & Parts Operations, Electronic Service Information...)

While air would indeed travel up from the lower hose, I can't see it staying there. As this problem seems to be constant, I was saying that the radiator would have to be very low to keep the light on, and every time I've looked at it I've thought to myself that by the time that low-placed sensor did trip, the gauge would probably be round the dial

Regarding the Oil Level sensor, they completely redesigned the system, and they are not interchangeable. The original was a 3-wire sensor, and the later one is only 2. I wish I had a picture to show you of the one that my brother pulled out of a '95 or '96. It is a heavy glass capsule with a whole circuit board inside of it. It has resistors, an 8-pin DIP IC and, I assume, some kind of inductive or capacitive sensor. The 2-wire job for my '97 is simply a reed switch with a plastic-coated magnet that floats around it. It's also 1/3 the price of the earlier one...

It's possible there is air in the system, it can be bled out at the thermostat housing (bleeder screw on top!). The question is WHY was there air in the system? There shouldn't be unless it ran low, which means it is losing coolant somewhere. If it's losing coolant, I'd suspect the lower intake manifold gaskets, there is a lot of documentation about DexCool antifreeze becoming corrosive to plastic when it gets old, so even a low mile car can be susceptible to this issue. There are plenty of other ways to lose coolant, but as AA said, head gaskets are not usually one of them for these motors, and there is an aluminum intake gasket available.

Good luck!

Light comes on and goes off intermittently. No mods, Temp stays rock solid at 200 degrees. Water level stays the same. Seems that this would mean a bad sensor.

Any other thoughts on what it could be or what is involved in changing?

Thanks in advance.

More than likely a dirty sensor or bad connection at the sensor.
Have you checked yet?
If electrical connection is good, drain some coolant, remove sensor, clean probe if dirty or just replace sensor.
IIRC, it's in the passenger side of radiator about half way down the tank.

isnt there a way to check sensors with an ohm meter?

Have you ever changed your coolant?

yeah why?

I changed the coolant at 100,000 and 200,000 miles. The 200,000 mile change/flush was done April of 2008.

robotennis61 wrote:

isnt there a way to check sensors with an ohm meter?

Yes if you put them in a pan of water and heat them while checking resistance across the connections. Too difficult to get accurate readings in my opinion. Much easier to just change the sensor.

I had old nasty dexcool leave a coating on everything on a different car and sensors like that didn't work right. I don't know if it could be wiped down or cleaned if you remove it, but as long as the wiring is decent, it will be more reliable just to replace the sensor.