After I got the AC on the 1978 working I noticed that the temp guage runs a little higher when on the hiway. Last year I installed an large aluminum radiator with a 3,000 cfm electric fan with a shroud mounted on it. I wanted to throw as much cooling at the car as I knew how so I would never have to deal with over heating.
Now when I drive for a while (something over 30 minutes) with the AC on the temp under the hood gets HOT. It's so hot under there that I cannot touch the air cleaner on the carb. The hood prop is so hot that you have to set it very fast or you'll get burned. It seems to be toooo hot! I think it's about 200 degrees everywhere under there.
After pondering this for a little while I realized that the electric radiator fan does not point at the engine like a belt driven fan, it points down at the same angle as the radiator so there is not much air moving across the engine.
I don't see any way to vent the engine compartment without punching holes in the hood (which I don't want to do).

Any suggestions would be appreciated.

 

Here are some basic questions/suggestions:

Components in the engine bay of Corvettes get very hot even when the cooling system is working correctly BUT you definitely should trouble-shoot the system anyway....it may be getting "a little too hot".

3000 CFM should be PLENTY to cool the aluminum radiator even with it pointing downward....you could add a metal deflector to direct the air from the E-fan onto the engine, rather than ruining the hood.

Change the engine coolant if it is a few years old.....make sure it is at the correct level in the overflow jug.

Make sure the condenser in front of the radiator isn't clogged with dust/dirt/grime/leaves/etc.

Make sure the thick foam strip across the top of the radiator is there to seal when the hood is closed....it has a big effect on cooling.

Make sure the thermostat is opening at the correct engine temperature.

Make sure the electric fan is turning ON when the temperature gauge shows that the engine is at it's normal operating temperature (the electric fan "switch" could be defective/out of adjustment.

Make sure the electric fan is blowing in the correct DIRECTION.

Make sure the lower radiator hose isn't collapsing/kinking when the car engine gets hot (I bought a hose that had an internal spring that prevents collapsing/kinking)

Check the engine timing to make sure it is set correctly.

(I had to add a 2100 CFM electric PUSHER fan to the front of my condenser to assist the puller fan and get the best airflow through the condenser/radiator because of a similar problem).

 

It sounds to me like you have an issue with the fan. I've never heard of anybody else having this problem after switching to an electric fan.

If you've finished troubleshooting items from previous post and have convinced yourself the situation is the new normal....
I would recommend exhaust/header wrap on your headers/manifolds and any portion of the exhaust that is in the engine compartment. This should help reduce underhood temperatures significantly and allow the engine to breath relatively cooler air. This should have a positive impact on all temperatures.

 

3000 CFM should be PLENTY to cool the aluminum radiator even with it pointing downward....you could add a metal deflector to direct the air from the E-fan onto the engine, rather than ruining the hood.
Good idea, sounds like something I would need to make

Change the engine coolant if it is a few years old.....make sure it is at the correct level in the overflow jug.
It's about 6 months old

Make sure the condenser in front of the radiator isn't clogged with dust/dirt/grime/leaves/etc.
It's brand new. Replaced it and the compressor when I had the AC worked on.

Make sure the thick foam strip across the top of the radiator is there to seal when the hood is closed....it has a big effect on cooling.
There's a foam hood liner that seals to the radiator mounting frame. I was thinking about trying to open that up so air could get in there.

Make sure the thermostat is opening at the correct engine temperature.
I can check that. The gauge says about 195

Make sure the electric fan is turning ON when the temperature gauge shows that the engine is at it's normal operating temperature (the electric fan "switch" could be defective/out of adjustment.
I adjusted it to turn on at about 195. The fan always runs when the AC compressor is on.

Make sure the electric fan is blowing in the correct DIRECTION.
It is. There's a large rush of air coming out behind the front wheel when the fan kicks on. It heats the garage in the winter.

Make sure the lower radiator hose isn't collapsing/kinking when the car engine gets hot (I bought a hose that had an internal spring that prevents collapsing/kinking)
I've never seen it collapse but I'll check that for sure

Check the engine timing to make sure it is set correctly.
It is

(I had to add a 2100 CFM electric PUSHER fan to the front of my condenser to assist the puller fan and get the best airflow through the condenser/radiator because of a similar problem)
The temp gauge never gets above 210

DO the components under the hood get to radiator temperature normally?

 

That sounds easy. I guess I get that at Autozone or some parts store.

 

Check out this thread. I think this is what you are seeing. If it's hot outside and you are running the A/C I believe you could reach something near 200* under hood temps. I know mine on a 95*+ day gets so hot under the hood that I cannot touch anything for any period of time either.
Notice that all those temps were with the A/C off. A/C on adds a significant amount of heat to the equation.

Headers add heat. Timing retarded to the stock setting will also.

https://www.corvetteforum.com/forums...g-results.html

 

This is great. Thanks for the link. I did a search before I posted the question but I did not turn up anything. Guess I didn't do the search right.

 

Yes...they get hot to the touch...I use a paper towel to unscrew the aircleaner hold-down "nut".

 

I bought a weather stripping set last year and I have not replaced the one that seals the hood to the firewall. Since that one is going away I was thinking about cutting it up into one inch segments and putting about 6 or 8 of the segments back in there. This would unseal the back end and allow heat to escape. If it doesn't work I'll just put the new one back in.

With the engine COLD remove the radiator cap and let the engine idle...you should see coolant swirling each time the thermostat opens.
If I start the engine with the cap off within about a minute coolant starts rising over the neck and spilling out. I wonder which behavior is normal?

With the A/C on mine will hit 200* but drops within one minute to 195*....then it repeats the cycle....on the highway the temp stays at 195* constantly
Well that's something for me to shoot for. Mine sets at about 210 with the AC on at 80mph with 90+ degrees ambient. Going slower like 45mph it doesn't run as hot.

 

By the way, how do I get a little picture to show up under my name? I uploaded a little one (256x180 pixels) but it doesn't show. Do I need to pay dues first?

 

This is a bad idea. If this seal is not in place or leaks, hot engine compartment air will be drawn into the cowling, exiting the cabin vents and substantially warming the cold a/c air (and fresh air when the a/c is off.)

 

I understand what you're saying. Glad I asked.

 

How I found this out was my fresh (outside) air vent was always putting out 90 to 100 degrees at the vent (a/c off). I read an article one day explaining the importance of this seal. Mine was in place but being the original one, I replaced it. I immediately took the car for a drive and was amazed when the vent temp was that of the outside air of about 75 degrees. Then I tried the a/c and the temp had dropped from 46 to 40.

 

I had an ah ha moment this weekend. We wend for a cruise through the twisties in N Georgia. AC off, ambient outside temp less than 80 degrees, driving for viewing not racing, the engine temp got to 210 at one point and never dropped below 200 after that.
I'm pulling and replacing the thermostat and doing a serious engine cooling system flush.
I'm tired of it getting hot. I spent almost $900.00 on a radiator and fan so I would never have to see the temp gauge go above normal!