Hi All,

Sorry for the long story, but I wanted to give all the details.

Here's my problem, while sitting in bumper to bumper traffic in Carlisle last night for 15 minutes my 93 LT1 overheated and spit up about a gallon of anti freeze. After she cooled down, I poured in about a 1/2 gallon of distilled water and when traffic let up we were able to drive her home the 30 miles to our house with the temp hoovering around 180 while we were moving, but rising to around 220 if we stopped for any length of time. Until yesterday, we never really sat in traffic for more than a few minutes since I've had her, which has only been a couple of months.

When we got up in the am I pulled the thermostat and tested it in boiling water and it works fine. I was tempted to flush out the system, but the mix looked pretty good to me, although I don't have anything to test it with. I did top it off with a 50/50 mix and also threw in a bottle of Water Wetter. I checked for debris stuck to the radiator and could not find anything. While playing around some more I noticed the fan was not kicking on as the temp rose above 220, unless I turned on the AC. I decided to test it out by taking a road trip and went back to Carlisle today.

On the trip up I ran without the AC on and had no problems as long as I was moving at a steady speed (temp stayed under 180), but if I had to stop at any lights or wait to enter the fairgrounds, it would steadily rise to over 220. I didn't want to take any chances, so I turned on the AC as I entered the fairgrounds and it dropped to about 210 by the time I parked. Since I knew I was going to be in bumper to bumper traffic when I left today, I turned the AC on right away and it stayed a steady 180 for the entire ride home and again I sat in bumper to bumper traffic for at least 15 minutes.

So I'm thinking either something is wrong with the fan itself or some switch/relay/sensor is malfunctioning. What do you guys think?

Thanks in advance!! By the way Carlise was way cool, it was my 1st trip.

 

Normally main fain is not working till temp reaches 228.
If your rad puked at those temps listed i would test your rad cap.
Check for crap in front and between rad and condensor.
Good Luck !! :cheers:

 

Thanks Dan, I'll check that out. From the readout on the gauge today, I'd say it was up to 240 and the fan still had not kicked on; that's when I turned on the AC. Not sure where the temp was when it puked yesterday, the wife was actually driving and I was ahead in my 69 coupe at the time. By the time I got back around there was a pool of the green stuff running down the street.

 

Here is what your problem is.... global warming and starting your car.

 

When are the fans suppose to kick on for a 91? :confused: i would like to set mine so both kick on at 180* and stay on unless im moving over 40.

 

Well, first, where did the coolant come from? Did it come out of a hose, the overflow tank or the radiator cap?

Second, the first fan should turn on at ~228 and the second at ~230 (I can't remember at the moment). Anyway, it has to be really hot before the fan turns on. I'd pop the hood, start the car and let it warm up. If she "pukes" again, you'll be able to tell where it's coming from and the fan should turn on around ~230 as indicated on the digital water temp guage.

Third, when you say you checked for debris, how did you do that? You have to remove the fan shroud/cover to see the radiator. How many miles on it?

The fact that your fans turn on with the AC indicates the ECM is controlling them properly (as long as you don't have any codes being reported by your SES light). Also, the fact that the temps actually start coming down when the fans turn on tells me there is air flow through the radiator (at least enough to cool the water somewhat). I suspect that you're not waiting long enough for the temps to rise sufficiently for the ECM to turn the fan on. I know, it's an agonizing wait, but that's the way those engines were designed.

Finally, you shouldn't boil over even at 240. I've personally seen an LT1 (my old 92) go to 245 with both fans running and it didn't spew any fluid, but boy howdy was that radiator clogged! :cheers:

 

Very common, from what you told me, your system is running fine. Check the cap, and do one of two things:

1. Get a switch to manually turn on the fan (I did that for a while, but it gets old)
2. Have Jesse or somebody change the temp which your fan kicks on. I have both of mine coming on together, I like it that way.

I know it scary, especially with aluminum heads!

 

Shawn,

The coolant came out of the overflow tank.

I did let it warm up in the garage and let it get up to somewhere between 230 and 240 and the fan did not kick on. The needle was approaching the "red zone" and I didn't want to watch it puke up coolant, so I switched on the AC. I guess I'll have to let it go and see what happens.

She has 84,000 miles on her and I don't have any service history. I did not remove the shroud/cover, I just peeked underneath and did not see anything, but if it stays cool w/o the AC on on the open road wouldn't that indicate it's getting decent external air flow?

Like you said I guess I just have to wait and see if it will boil over. I did notice it was cooking in the overflow tank when it got up to around 240, so maybe it does just need a good flush job and I have yet to see the 2nd fan come on, but again maybe I'm just not waiting long enough.

 

Sounds like you have a couple of problems. First check the main fan to see if it is operational. Run a jumper from the battery directly to the fan. If it dosen't spin it's bad. Also, even at 240* you should not be "cooking" in the recovery tank. I'd look at the rad cap. It might not be holding the required pressure.

 

I hate to sound stupid, but I just want to confirm that the main fan is on the drivers side, right?

 

Yes.

You might try to pull codes. I doubt you'll get anything, but they are free. http://www.c4vettes.com/codes.htm

 

You need a new radiator cap. :thumbs:

 

If the AC turns both fans on, then obviously, the relays and fans are working properly. Make sure though.

 

what do you look for in a faulty rad cap?

I'm pretty sure, but not 100% positive, that only the main fan was running with the AC, but I will double-check that tonight.

 

It isn't anything you can see the interior spring may have weakened. You'll need to have it pressure tested or just pop for a replacement.

 

I'm not a mechanic but, the fan should come on before the cap starts letting it dump into the overflow. I once dropped a small part that I needed to install an aftermarket air-intake system - and it fell between the radiator & air conditon condensor. I had to take off the radiator shroud to retrieve the part... and oh my! tons of leaves, debris and a burger king wrapper stuck between them! You cannot see this without removing the shroud. Simple to do. When I had my motor rebuilt, my mechanic wanted it to run cool for the first 5,000 miles so he shorted the the fan switch to run continuously, after the motor was broken in, he switched it back. My car has the Main Radiator fan between the radiator and the motor, while the A/C fan is in front (not side by side) Recently, I just had to replace the fan motor - no complaints it lasted about 190,000 miles. A new cap would be an easy cheap fix, try that first, then try trouble shooting the fan.

Good luck, stay cool!

 

OK, here's the latest - I replace the rad cap and the main fan relay - less than $20 total. The main fan doesn't kick in until the temp guage in the car registers around 260, but you can tell that the car is not running that hot. I had it sitting for about an hour just idling and it did not overheat, but the guage showed around 260 and the fans came on periodically. As soon as I turned on the AC both fans kicked in and the guage would drop down to 180. Could the guage be faulty? If so how do I check that and any idea what that would cost to replace?

Thanks again!

 

Have you compared what the digital temp guage reads with the analog? Is there any discrepency?

 

I compared the 2 this morning. It's about 77 degrees here right now. With the car idling for about 25 minutes the digital readout flucuated around 220, and the analog exceeded 260. When I turned the AC on the digital readout dropped to about 195 and the analog showed about 215 and probably would have dropped lower, but I don't have time to play with it anymore before I go to work.

Anything I can do to fix the analog?

I've got my eye on a 93 vert and the wife says I can't buy it till I sell this one (too many toys). I've got someone interested in this one, but they don't like this guage issue, which I can't blame them. Since I've only had her for a short period, I don't know that the analog guage ever worked 100%

 

OK, I just did some research on the forum and I found something about a possilbe faulty sending unit for the analog guage.

Anyone have any ideas what that might cost? And is it something simple to replace for someone who is not overly mechaniclally inclined? And if anyone would have a pic that would be fantastic.

As usual thanks for all your help, this place is the greatest! Some day hopefully I'll be answering more questions than giving them! :D