My low coolant light came on this AM. I topped off the coolant overflow tank with antifreeze. Car was parked in the driveway (hill) nose down. Light goes off until I drive a few miles. Then it came on intermittently (about 6 or 7 times) during my 45 minute commute to work this AM. During the drive home I didn't see the light come on at all. What might explain this behavior? Thanks. ~Juliet

 

Mine does this also. I guess there are 3 things we can try.

1. Get a new radiator cap as ours are not sealing tightly anymore with age.

2. Drain/change the coolant as it is past it's age and the pH level has changed causing the sensor to alert us.

3. Start the car cold with the radiator cap off and raise the RPM to 2000 and hold it there long enough for the thermostat to open up and let coolant flow through the block. While the RPM are up the coolant will fall down allowing us to add more. Add more and keep RPM up until air bubbles are no longer visable. Replace cap and then let RPM fall down to idle.

 

Also, possible that some air has gotton into the system. This ususally happens when working on the radiator or water pump or even changing a hose.

Vic

 

Here's some more background on the car - I had a new radiator / hoses put in this summer at Tony's Corvette. The green antifreeze is in the car now. I would think that it would last longer than 8 months.

Good point about the rad cap. I'll have to look into that.

As for running the engine w/ cap off etc... does it matter if the car is not level? I'm wondering if I just got a false reading on the full line on the overflow tank. I'll have to check it tomorrow AM after I back the car up the hill to the flat spot on the road (it block's the neighbor's driveway which is why I don't park there).

I was wondering if maybe the full sensor / sender is prone to failure. Where is it located? Maybe a wire got knocked is loose or has worn insulation from rubbing or something like that.

 

Yes it matters if the car is not level. You can get rid of air best when the car is nose uphill when you are "burping" the cooling system. Your car didn't have the low coolant light come on going home from work because the reservoir supplied coolant when the engine cooled while you were slaving in the salt mine. Today is the third day that I have burped mine and if there is a leak it is not detectable . I am not a happy camper at this point.

 

At my last oil change I distinctly recall the mechanic topping off the coolant - and that was less than 2,000 miles ago. So it must be going somewhere. :cry It's not leaking out when sitting. He's got a new rad & hoses. Maybe I should get it pressure tested?? :( You know I had the problem of the missing antifreeze with my Rustang - which was the final nail in the coffin which convinced me to sell that car and get a C4. Of course that was AFTER I got the new radiator. The old one was leaking between the rad and the plastic side tanks... How does that song go - "Isn't it ironic..."

Maybe I'd better check the oil in the AM too. Thanks for the advice. :seeya

 

Scorp, that sensor doesn't know from dittity if the coolant is good or bad, it just wants to be wet.

I went through this for a period with the 89. Convinced myself that the stupid sensor was bad, as most times the level under the cap was good. Then the level under the cap was low and nothing was drawn from the overflow. So I worked the overflow system: Replaced cap (it WAS bad), replaced the hose to the overflow (it Was cracked), installed clamps on the hose (none were there), cleaned out the overflow container and checked for leaks (none). Topped it all up and packed it good. Great. It dang near emptied the overflow in less then a month and the coolant level was low again.

Finally found the leak. On mine it was the aluminum tube the runs around the oil pan from the combo heater hose to the oil cooler on the filter mount. It was very difficult to see this leak, but when I got it out I found a crack and the tube (pipe) had been hitting the cross brace on the frame. Replaced the tube and all is well for over a year. Light never comes on.

I'm convinced that this leak allowed air in, but little coolant out. Only toward the end did I finally notice a slight amount of leak. So I think the coolant was expanding into the overflow tank, but the leak allowed air to come in to replace the coolant when it cooled. Think leaky cap / overflow system may do the same thing.


Also add, make sure the heater is on full hot when packing; you need that coolant getting through the heater core to get rid of all the air. Also you can never get all the air out, takes about 100 miles or more of fully warm operation and a sealed overflow system to get most of the remainder out.

Good Luck.

Pete

 

:confused: When did they start using the ones that did?

 

Don't know, I'm just getting up to speed on the old ones! :D

 

Dayum, You're good Pete! :cool: BINGO! :cheers: I'll bet ya that's what it is on mine too! I've got a new overflow tank, hoses etc... But I DO have an oil cooler on my car - that was an option in '87 I believe. :cool: ~Juliet

 

I hesitate to suggest that that tube is your problem also. The failure in mine was caused by a poor installation of the heater hose. It runs from the heater core to this tube and is the one with the tee connections on the passenger side to feed a bunch of stuff. Well whoever put the last one in just pushed it down hard on this tube which bent the brackets that hold it to the old pan and let it contact the frame. After a while this aluminum tube just gave up and cracked. The new tube and heater hose, now properly installed, are a good inch over the frame. I also slipped a peice of tubing over the possible contact point just for good measure.

Here is a picture if it will load from my sight:
http://members.home.net/pcluscombe/f...alcoolpipe.JPG

It is sort of hard to see, but the 90* bend near the top is where the problem happened. Any leakage would have traveled up and down the cross braces on the frame and who knows where it would have ended up.

The connection point is on the front of the engine, passenger side. It's behind the belts and near the input to the water pump. Right near the fuel lines. Very hard to see. You can see (if my link works) where the contact point is in relation to that. The tube mounts to the oil pan bolts (I really dislike that).

While I was under there I took the torque wrench to the oil pan bolts and got quite a bit out of them.

Hope the picture works and is helpful.

Pete

 

Point taken Pete. Thanks. Well I guess I'll have to try burping him nose up in the driveway tomorrow AM. Then this weekend I'll have to schedule some garage time (3 vettes - 2 car garage!) to jack the car up and take a good look underneath. Do you think there's any value in having the system pressure tested at the local garage? I know they've got one of those things there which they put on the rad cap to test for leaks. It might be worth the $15 or whatever they'll charge to take a quick look for me. Hmmm - I might just do that tomorrow. They can put it on the lift for me too... Thanks. ~Juliet :seeya

 

Pressure test would have saved me a lot of aggravation! This is a good idea.

 

Well, I had them pressure test it this AM. Seemed to hold the pressure OK. It leaked down a little bit - but that took about 10 minutes to go from about 20 lbs to 15 lbs. So I'd guess that's within specs ?? That leaves me with the radiator cap. I'll order a new one and see if that clears it up. As a matter of note - the coolant light was not on in the AM, until after we had taken the cap off and run the test. Then it came on / off for about 10 miles at which time it stayed off for the rest of my 40 mi. commute. I looked at the oil cooler line - and on mine it is pretty close to that front cross member piece, but it didn't feel like it was gogued or rubbing or anything - I didn't want to get too dirty on my way into the office - that spot needs some cleaning! :lol: ~Juliet