Please help... our 95' has been running hot. When we drive for over, let's say 10 miles in start/stop traffic, the car's temp gauge generally touches the hash marks on the dial - 240-250 degrees. The car has even hit 255 and tripped the warning light once. The outside temps have been over 90 lately, but I know this isn't normal. The strange thing is that the car usually gets close, but never truly overheats. The coolant in the radiator looks good and the reservoir is full. Can anyone give an idea before we take it to a dealer? Thank you!

 

stay away fromt he dealer, they ahve no idea but to ask you to take out ur checkbook. i had the same problems, i looked on here for about a month and its fixed, go threw a checklist, search for other posts, but heres what ive learned and what hellped...ok, take off ur radiator cover.( shroud) and hose her down, pull it out if ur worried about getting things wet but i wasnt. and u will see soo much junk in there. i could have filled a 2 liter. and then flush the coolant and just do normal checks. but after i cleaned my radiator i wont go over 210. EVER. even sitting around with a/c on. hope it helps others will chime in.

 

...check your pm's.....

 

also check to see if your fans are working.You may also want check the radiator cap and thermostat.

 

I also have a 95 and was having overheating problems.

You want to check in front of your radiator for debris, Corvette are "bottom feeders" and can suck a lot of junk -leaves, plastic bags etc. which can partially block your radiator. (If you use a hose to clean the radiator, be very careful using water near the Opti !!!! 95s opti is supposed to be safer (waterwise) than earlier ones however with the tremendous cost of replacing one, it is better to exercise extreme caution.)

The LT1 engine are designed to run hot. The fans don't start until around 225 degrees. Turning on the air conditioning activates both fans. This is a good way of checking whether the fans are operational. If the temperature is rising excessively turn on the air conditioning. (I know that this is exactly the opposite of what you father taught you. Normally one turns off the air conditioning when a car overheats.) Experiment with this a few times in non critical situations so you'll have an idea of what the normal readings are on the temperature gauge when the fans are activated.

Also rely more on the digital gauge for temp readings as the analog gauge (at least in my car ) reads high.

In an earlier reply eventr mentioned getting a new radiator cap. This is a good idea. They are dirt cheap. Get a new one from the dealer if possible, as some of the replacement ones are defective. Also the LT1 engine needs a special cap and a generic one won't do.

In the middle of the 1995 model year GM switched to Dexcool so some of the 95s have the green stuff and some have Dexcool. Dexcool is orange. Mine had Dexcool (orange) in it when I got the car.You'll find a lot of pro and cons regarding Dexcool on this forum. I decided to stick with it as it was what came with the car.

My car was overheating badly in heavy traffic though every thing seemed to be working okay (fluid levels etc.) I cleaned out some debris in front of the radiator but didn't think it was enough to cause the overheating problems. What I did find was that when I stuck my finger down into the surge tank (under the radiator cap) I had almost an inch of sludge so a radiator flushing was the next step. To do a proper flushing you need to remove the knock sensors but this wasn't practical ( no hoist) so I flushed the system several times with distilled water. I used my shop vacuum with a few pvc pipe part modifications from Home Depot ( size it down to a 1/2 inch pickup so I could get into the tank) to suck the sludge out of the tank. You can also use the shop vac with the hose on "blow"and hold the hose at the radiator cap and it does a better job of forcing out the coolant/water thru the drain at the bottom of the radiator ( right hand side, on the inside). Remember to turn on the heater so that the heater core will get flushed too!

The plastic expansion tank I removed and cleaned. I found the easiest way to do this was to use some pebbles(pea gravel size) and slosh them around with a little gasoline and then do the same with soapy water followed by a lot of rinses. I also inspected all my water hoses and replaced a couple that were a little "soft". I then added new coolant-(Dexcool) (Use distilled water if you mix your own) and a new radiator cap. You'll need to get all the air out of the system by "burping" it.
Bring the engine up to temp several times and then allow it to cool down. When the engine is cool, add more coolant as necessary. Remember to turn on the heater so you'll get all the air out of it too.

Look up radiator flushing and "burping" in the Forum Search as others have written a lot of good info on these subjects.
The other possibility that maybe causing the overheating is a stuck thermostat which I haven't gone into here. I'd try a good flushing first.

If you haven't done so I'd read up on Dexcool. Apparently one of the things you don't want to do is mix dexcool and the green stuff with each other. There are some newer coolants that are supposedly compatible with both types. You'll hear a lot a badmouthing on Dexcool. I decided to stay with it as I think most of the problems with it center around neglect. We change our oil at 3000 miles religiously yet ignore the cooling system. From now on I'm flushing and changing coolant once a year.
Hopefully just a good flush will fix you overheating problem. It sure made a world of difference with mine.

 

What's the digital temp gauge show?

 

http://gmtips.com/3rd-degree/dox/tips/cool/cool.htm

 

A water pump that is on it's way out will cause tempature problems as well. Check for any weeping beneath it and for any odor of coolant.

 

Go thru the check list:
1. Radiator cap, replace.
2. Hoses, upper and lower, also replace.
3. Clean your radiator, inside and out
4. Flush, complete system and replace w/ 50/50 distilled water and antifreeze.
5. Thermostat. Make sure it works and is the right one for your driving. Make sure yours works.
6. Use a synthetic motor oil like Mobil1 5W30
7. Make sure your fans work, if not, fix them.

The above is low cost and easy to do and should bring down your temps.