I just flushed and replaced my thermostat and radiator cap. The temperature gauge on my 1994 corvette gets up to 240-250 when idling for about 30 minutes. The hoses all read about 190-195 so I assume its not actually running hot. This only happens when idling. Never happens when I am driving it.

Any suggestions??

Thanks

 

Look at the digital temp gauge and ignore the analog. Did you pull your knock sensors off and flush? If not you left alot of rusty crap and a gallon of undistilled water making your mix off.

 

Are you sure both fans are working?

 

Assuming the temp, to which you refer, is from the analog gage (?). What is the reading from the digital gage?

Hoses do not provide a temp reading. Was the hose temp provided by a remote temp sensor?

The LT1 requires a special t-stat....does your new
t-stat meet LT1 requirement?

Tutorial on LT1 t-stat:
All LT1 engines utilize a special 2-way acting full bypass thermostat. This means that the thermostat regulates coolant flow both in to as well as out of the engine, while the bypass portion of the thermostat circuit supplies the water pump with a full flow of liquid coolant at all times. This is unlike a conventional engine thermostat, which only regulates coolant flow at the engine outlet, and which does not allow full flow through the water pump when the engine is cold and the thermostat is in bypass mode.

Both sides of the 2-way thermostat used in the LT1 are linked together, and a single wax pellet actuator operates the spring loaded mechanism at a pre-set temperature. When the designated temperature is reached, the wax pellet expands, opening the dual acting valve. All current LT1s come from the factory with a relatively low 180 degree temperature thermostat. Most conventional engines today use 195 degree thermostats in order to meet emissions specifications at the expense of power, durability, and reliability.

It is important to note that the 2-way thermostat is unique to the Generation II LT1 and is not interchangeable with older Chevrolet smallblock engines. This is particularly important if you decide to change to a colder 160 degree thermostat, make sure it is the proper dual acting type required by the modern LT1.

 

Good information on the quirks of the reverse-flow cooling system. But I wanted to clarify something for anyone who might think like I do: When someone says "modern LT1" I think of the aluminum 6.2-liter engine in today's Corvettes, Camaros, Cadillacs, etc. Aside from the pushrod valvetrain, that is a modern engine and it is called LT1.

I'll go out on a limb and say that the LT1 in the C4 Corvette is generally not considered a modern engine.