Hi Guys
well I have the problem in my C4 L98.
10minutes normal driving and i have temperature like below.
Fan is working normally (i have manual switch to turn on the fan)
Fuel Pump changed 3months ago.
It can be Thermostat or You goni It could be the different one?
thanks!

 

At idle that water temp is normal, should drop when fan turns on at around 235*, that temp is high for going down the road, should be closer to 200* with a stock t stat. You will find that the oil temp is usually 20* warmer the water temp when fully warmed up.

 

thanks Mate
well last time I drove ca. 30min normally and temp decreased till 248F and stopped the car to cool down everything.

 

Something is wrong. Flush the cooling system. I mean really flush it clean. Pull the radiator and clean. Blow out the condenser from the backside. Replace the thermostat and radiator cap. I know it sounds like a lot of work. My 96 runs down the road at 188 deg F. Dan

 

If going up that quickly I would think something is wrong.

Flush coolant, fill with new 50/50 ratio, probably best to just change the t-stat. Inspect WP to see if its weeping at a minimum.

If its still doing that and the fans are working normally, then clean the area between the radiator and condenser.

 

Vader I'd do the last thing you said first.

 

I agree with Vader86 and Whaleman!

A lot of people are not aware that your Radiator Cap "wears" and can in fact wear out and not hold any pressure which leads to overheating. The Cap needs to hold pressure to allow the cooling system to work. I replace my radiator Cap and Thermostat every 10 years regardless.
The little front air dam/Spoiler that pushes air into the radiator is very important as well, especially if your Corvette is getting that hot while driving. It forces air through the radiator allowing the car to run cooler.

Rubber hoses that are too old can collapse at speeds when they get that hot. A collapsed would cause a fast temperature rise like you are seeing. The speed at which your engine warms up concerns me.

Between the radiator and Condenser you will probably find a forest growing, it happens. You should see the pictures of what people pull out of their Radiator shroud.
Be sure that your air is passing through the radiator and not going around due to bad or missing seals.

I too believe in 50/50 anti freeze and even more distilled water if you live someplace where it does not freeze. Anti-Freeze does not help cool your Engine, the higher the concentration of Antifreeze the less heat it can transfer. I still add a bottle of Red Line "Water Wetter" to the coolant. The Water Wetter helps remove heat by helping rid the layer of air bubbles that form on the metal inside the engine block. It allows the coolant better access to the metal surfaces and helps keep the engine cooler.

You can remove the corrosion on the aluminum surfaces of the condenser and radiator using a "Coil Cleaner" Spray designed for Home AC systems. You spray it on and let it sit for a couple minutes and wash it off with open hose end, don't use any pressure on the fins as they bend way to easily. The coil Cleaner is something they do to Home AC systems when they service them. The Coil Cleaner is great stuff as it removes decades of corrosion in minutes and then the radiator will be able to get rid of more heat. The only thing is you have to be careful around painted parts as the cleaner can damage the paint if left too long.