I've owned my '95 since Feb 2006. In that time, coolant temps (monitored on the LCD) have consistently run 194 - 196 F at highway speeds, and about 10 - 12 F warmer when I'm in traffic (small town traffic; not stop and go; and only if AC is OFF - with AC ON, temps stay under 200F). This has been true early in the driving season as well as mid summer.

Today was my post winter shake down cruise. Temperature in NW Illinois this morning was around 55F.

At highway speed (70 MPH), I noticed that coolant temp was running 204 - 206 F. When I exited the freeway, temps dropped on the off ramp down to 200F. Running in town at 45 MPH, temps started slowly climbing back up. Coolant temp stayed at approximately 205F when I was heading back to the house (30 MPH).

The coolant reservoir is full, and was cool to the touch when I got home. The radiator fill tank was hotter to the touch, but not uncomfortably so. The upper radiator hose was about as hot as I expected it to be - hot to the touch.

There is no tell-tale smell of coolant leakage, nor any sounds of coolant leakage. The area between the evaporator and the radiator (looking through the side of the shroud) is clear of significant debris. I didn't look under the car at the actual air intake area - that's next on my list.

The upper radiator hose is firm - pliable, not hard, but no indication that it's collapsed. I didn't get a chance to check the bottom hose.

After the car cools, I'll be checking the upper tank to see if the coolant level is low.

I don't suspect that the radiator fans have failed, since they don't have any significant effect at highway speeds.

If coolant level is OK, then I'm thinking my next step is thermostat.

Any other suggestions?

Thanks,
Steven

PS Oil temps were normal; about 200 - 210F after warmup.

 

Sounds more like an airflow blockage to me.
I think you are familiar with what the temps should be (or at least what you have always experienced in the past).

Crawl under the nose and take a good look up in the air intake cavity, and make sure there are no obstructions.
Might be time to actually remove the radiator an perform a good cleaning.

I believe if it was your thermostat or coolant level, you would have seen much higher temps.
Coolant level would have tripped a low coolant light also.

 

Most likely you've picked up some grass, leaves, maybe paper or plastic bag. On a 94 you can look through and opening on the passenger side and see between the radiator and the a/c condensor. Maybe the same on a 95. As said, take a flashlight and look up under the nose at the front of the condensor fins too. You can gently use one of those long skinny brushes made to clean clothes dryer vents. Just try not to bend any of those thin cooling fins with the brush. It's surprising how much gets sucked up in there and sticks. A McDonalds bag can block about 10% of the airflow.

 

I took a look underneath, and there's no significant collection of debris, leaves, or plastic bags. I also checked the area between the evaporator and radiator (passenger side), and there's nothing visible there, either.

The system is full at the radiator cap, and the coolant recovery tank shows that it's at the right height.

Steven

 

Well, I finally got enough time to replace the thermostat, and that seems to have done the trick.

Highway temps are now running between 188 - 193, with slow city temps (AC OFF) about where they normally go.

We'll give it a good test on Friday, when we take our four hour jaunt from NW Illinois to Champaign for Bloomington Gold!

Steven

 

My 95 on the hwy can go as high as 203 with a Dewitt's radiator and stock 180 stat.usually around 200.That would be a long ride.Never had highway temps at 188 - 193.I do have the perf.rear 3.07 maybe that is why my temps are a bit higher.

 

That's interesting - I"m running a 4.1:1 rear gear with my six speed. Engine speed at 65 MPH is only about 1700 RPM. When I was having this issue, engine temp in sixth gear at 65 MPH was 204 - 208, but if I downshifted to fifth, the temps would fall to around 200.

I concluded that my thermostat was opening some, but not fully. It seemed to be closing because the engine came up to temperature at about the same rate as before.

If my temps had always been like yours, then I probably wouldn't have thought anything about it. It wasn't so much the absolute temperature - it was the odd 'step change' from several years of consistent performance, and then something new. I don't like things that like that to happen!

Steven

 

And i thought i was the only vette owner to use one of those dryer vent brushes? It works on my 93. Now if i can just get the highway dept. to stop blowing the grass and weeds into the road instead of the ditch! I think i read somewhere that a long gone chevy/corvette engineer conspired with the state of Virginia to help sweep the roads with OUR corvettes! I know i know i should have started another thread!

 

One more thing I would like to toss in for you 95 owners, I just installed a new Radiator a few weeks ago in my 95, and found out that while replacing my 10mm hose.. at the radiator "T" on the surge tank side of the "T" is a "Restrictor" that was completely plugged. I would not have found this if I did not Cut the Swedge fittings in order to replace the hose..

With OAT's of 65-105° I Cruise at 70-75mph @ 188° constant

edit; It's a brass fitting pressed into one of the two aluminum tubes that run up the wheel well.. so it's were the T connects to the aluminum tube,, under the rubber hose.

 

I will check mine but I did replace hoses about 4 years ago.thanks for the tip.What rear axle do you have 2.59 was stock.I have the 3.07 which in turn revs a little higher than 2.59 which could add a few degrees to the temp

 

Only had 2 weeks, took on scenic trip in heavy stop and go traffic. Guage showed 240 and I got concerned. Went back down to 200 in clean air. Had coolant flushed and thermostat replaced. Fans were checked and they work, they did say that dash gauges showed higher than actual digital readout if you push "gauges". Basically it was ok they just run hot unless you have clean air.

 

Richard,
Always use the digital gauges as they are more accurate

 

In fifth gear @ 65mph my digital and analog guages are showing 189-192F.My car is a 1993 MN6 Coupe with 3.54 gears and a stock radiator.The only change I have made to the cooling system is a 180 thermostat in place of the factory 195 unit.I know that LT engined Corvettes run rather hot but the temps that I'm seeing on yours and other forum members seem high.

 

As far as I know the 93 use a 180F from factory.

 

What about going to a different coolant switch that cuts the fans on at 200 and off at 185? Live in FL, hot! Coolant flushed and thermostat replaced already. Could replace radiator but don't want to, 94 with 22000 miles on it.