I've been having an odd problem with my cooling system lately. The low coolant light will come on, and the car will run hotter than normal. But when I check the coolant it is topped off First time I waited for the car to cool off before I checked the coolant, it was ok. Next time I checked the level right after I stopped the motor. I put a towel over the radiator cap to keep from getting sprayed, and once again, it was topped off. The car runs about 25* warmer now(but only when the low coolant light is on) than it did before. I have no explanation on why it is running hotter now since it is fall and is quite a bit cooler here. Someone help me out here, this is blowing my mind!!

John

Edit: need to add that the low coolant light is only on about half the time.

 

I know you guys hate bumping stuff up to the top, but I posted this a day or two ago so I think I'll be in the clear. Hopefully someone will see this and can help me!

I am leaning towards a bad thermostat, but money is really tight right now, and I don't want to start replacing parts hoping that it will fix the problem. I checked the coolant today, and it was a little lower than usual, about 2 inches below the cap, so I topped it off and it was ok. I really wish I could read how much coolant there is in the overflow tank, but I just can't read that dipstick!! Usually I pull the stick out, and if some coolant drips off the end of it I'm satisfied with the level

 

Well, check that level in the overflow better than you usually do. Add more to it. Bleed the air out of the cooling system. If it was a "little" low when you checked it today then it probably needs the air bled out. Oh yeah, I just remembered. My car started running hot last year when my heater core became plugged. Acted just like a bad thermostat, would run hot but cooler air than usual from the heater. So maybe you're due for a flush.

 

u need a coolant senser i had that problem 2 or 3 times already in the 3 z28s i owned not a thermostat

 

The low coolant sensor is on the passanger side of the radiator, a few inches down from the top. If the coolant level isn't below the sensor and the light is on, the sensor is defective. They're expensive - I think around $50-$60.

I unplugged mine so the light doesn't come on. When I did the engine seems to run warmer according to the temp. gauge. I wonder if the sensor is tied into the gauge somehow and makes it read different if the sensor is unplugged.

As for checking your overflow tank, pull the dip stick out, dry it off good with a paper towel and then check it again. It's difficult to read, but all you have to do is look for where it's wet to see the level. Not one of GM's better ideas

 

Thanks guys, I'll see what I can come up with.

 

Ok update, (and let me know if my reasoning is off here). I don't think the heater core is blocked because 1) when I turned the heat on it is hot as usual and 2) when I turned the heat on it did a pretty good job of cooling engine temp down.

I'm changing the oil right now, so I think I'll bleed the system next, and if that doesn't help look into a thermostat.

 

The low coolant light is an extremely common issue. The sensor in the radiator is going out and most people just unplug it. That light is not tied to the PCM at all. The sensor runs directly to the LED in the dash. There is no way the low coolant light can affect the temperature at which the motor runs.

As far as why you are running 25' warmer in the fall than the summer, well, could be a few things. Maybe it's time for a radiator flush, or maybe you're not running the A/C anymore due to cooler temp outside and therefore the cooling fans aren't running as much. Are both of your fans working?

What temp is your gauge reading? Maybe the sending unit in the head is going out and the gauge isn't accurate anymore?

Bottom line, unless you're gauge is reading in the red, I wouldn't worry about it. If you want it to run cooler, then get a 160' stat and mod your fans to come on earlier.

Hope this helps,
Thomas.

 

The fans have been reprogrammed to come on sooner. They come on at 185*. To give you a reference point, in the middle of the summer sitting in traffic, the coolant temp hovered around the first tick on the gauge(about 185*). Now the temperature even when I'm driving at a constant speed about 55mph in cool weater it has been hovering around the halfway mark(210*).

 

Do you have the ability to scan your PCM? If so, do it and see what it reads for temp. The PCM gets the engine temp from the sensor in the water pump, while the dash gauge gets the temp from the head sensor on the driver's side. I wonder if your gauge is accurate?

Also, like already suggested, make sure your coolant system doesn't have any air in it. There is a procedure for bleeding the air out of it.

If you let the car idle, do both of your fans come on? Have you verified this with the hood open and motor running?

Thomas.

 

did you check your rad cap make sure it seals and the little metal valve is pulled againts the rubber.

i had a problem with my water pump last week the impeller was loose on the shaft causing it to spin less or not at all! it ran warmer than usual then it started to overheat.

i had a problem ith my car overheating last year it was the cats were plugged

i would have to agree with th ac theory also!

all sugustions based on my camaro cooling system woes!!!

it could also need to be flushed run some rad flush for a day than take it to get flushed!!

 

Both fans are coming on. heading down to the garage to bleed any air out of the system........

 

Did you check for crap in front of the radiator that could have been swept up there during driving, plastic bags, newspapers, etc.

 

Ok, update time once again. I let the car cool down, checked the coolant level, it looked full and there was a good amount in the overflow tank. After some careful looking it was up to the "Full Cold" mark. Here's what I did-

Left the radiator cap off and let the car run until the thermostat opened. When I started the car up, the coolant level came up steadily until it began overflowing a little. Then all of a sudden a bunch of bubbles came up, then the coolant at the top became frothy looking because of all of them. Then the coolant level dropped until I couldn't even see it anymore in the radiator So I turned the motor off, but left the ignition on so the electric waterpump would circulate. I slowly added water to the radiator until it topped off. Then I started the car up with the cap on, let it warm up fully. At that point I opened the bleed screw up and let some coolant out. It didn't seem to have any air in it though.

At this point I'm just wondering where my coolant went The last time this happened it was due to a blown headgasket, but when that happened the car was puffing white smoke which it isn't doing now. I did see some signs of a few small leaks, which over time seems like they could be the cause of this. I would say that I'd keep an eye on the coolant level, but it seems to look full even when it's not..... hell I don't know what I'm gonna do