I'm sure you know this but half the radiator will feel cool while ht other half is hot because hot liquid goes in one side and cold liquid goes out the other. I only bring this up because you mention that "the radiator is cold" but if you are only touching one side it could be OK.

In any event, I'd pull the T-Stat and run the thing and see what happens. I had a hell of a time with mine, turned out to be a bad ground related to the thermostatic switch, which does not appear to be your problem. My fans wouldn't come on at all. I also noted that my temp gauge is off by increasing increments as the temp climbs.

 

My 78 will climb to 230/240 before the thermostat opens and then the gauge will immediately drop to 190/195, the correct operating temperature. Remember, these old 350 engines were built to run hot for emissions purposes.
My old 350 doesen't run very good until it reaches proper temperature and then .....away we go

 

Just an update. The new water pump cleared up the problem. The circulation is normal, the radiator gets hot like it should, and the gauge holds steady at 180*. Thanks to everyone that posted for your guidance. This forum is a great place.

 

Hello,

I've never seen this before...maybe someone has!

I have replaced the thermostat in my 1995 coupe with an LT1, 4 times now in the last 6 months. They all have stuck in the closed position casing the obvious overheating. Each time I replaced one, I followed the "burping" proceedures and intitially all was well. If I let the car sit for a week or two, sure enough, the thermostat will stick and excessive tempuratures happen within 5 to 10 minutes of starting the car. I have tried different brands, I even spent $38 for a GM brand and it stuck closed as well. Recently, I had the transmission replaced by a qualified garage who I trust. The car had been unstarted for about 3 weeks while the transmission was built and shipped to this garage. On the test drive for the transmission, the thermostat stuck shut and a proper test was not conducted. The tech called me and told me what had happened and recommended that the thermostat be replaced. I told them to go ahead, maybe they know a better way to purge the cooling system. I picked the car up and drove it home, checked out fine. The next day I started it up and the new (4th) thermostat is stuck shut. I mean the temp gauge is almost pegged and the radiator is stone cold, the heater is blowing cold air.....can anyone offer some advice?

Please help! Thanks!

 

I thought I had issues with the two t-stats. Have you verified they are stuck by putting them in a pot of water on the stove and using a thermometer (candy thermometers work best) to see what temp they are opening? If they are bad, try running without a t-stat and let the car sit the same time periods it sat before.

When I pulled my original water pump, all indications were the pump was good. The impeller moved with shaft movement and no bearing issues. My problem went away with the new pump. My 82 sits for days at a time and everything still works normally since the water pump was replaced.

Good luck on your fix and let us know what you found.

 

As master of the obvious, time to change the coolant. Maybe a bad mix, maybe just rust, but it's the constant to all t-stats.

 

You're low on coolant.

The heater will blow hot air if the engine is hot, if it doesn't it's because there's not enough coolant to circulate properly.