I noticed last night driving home that even with the cooler night air (about 80 degrees) that if I run around 70mph the temp gauge hovers around 200+, but if I backed off and ran around 60mph it would drop back down to about 190 or less. Does eveybody else see temp changes related to speed? I am currently running water with wetter water.

Thanks....

 

I have a similar situation but I'm using the orange anti-freeze. I also have a 3 speed auto tranny. When I'm running on the highway, my temp is a constant 210. My rad, pump, and hoses are all new. Any help would be great.

 

make sure all the foam seals are in place around the radiator and between the support and hood. you need all the air flow to go thru the radiatior, not around it. joe
ps, there are a bazillion topics on this subject, when the archives come back you can spend years reading up on it.

exaggerate? me? If I told you once, I told you a million times, I don't exaggerate! LOL

Joe

 

Temp and speed (rpm's actually) are for sure related. The more rpm's the hotter the engine and thus the hotter the coolant. Now you could also say that the extra speed will cause more air flow through the rad and keep the water cool. Thats true in a perfect world, but vettes tend to have a hard time collecting that air from under the car. The front spoiler has to be in good shape to be able to properly direct air towards the rad. Also the increased rpm's will make the water pump work faster and might start pushing water through the rad too fast, not giving it enough time to cool down (I doubt you have to worry about that though).

I got a question for you, are you running a thermostat? If so, what temp? If not, why?

 

also some time's the higher rpm's move coolant to fast, what
is your mix ??? did you flush system?

 

Many times people forget about the spring inside the lower radiator return hose that keeps the hose from collapsing. Just a thought.

 

I have electric fans, which theoretically should not need air forced through the radiator. With the electrics, higher rpms = high temps.

 

I just got my 76 vette a few months back and am working the bugs out. I have a cooling problem which I am going to start working on next week. Going to and from Glass on the Grass Corvette Show in Spokane I ran just shy of red line on the temp gauge at 70 mph and about 100 degrees ambient. If I droped back to 55 mph the temp fell back to just a little past half way between 200 and red line (this is with out A/C on). My thermostate and coolant is new and clean. The water pump looks as though it was replaced in the not to distance past as the paint and gaskets look new. Bottom hose has the spring in it. No vertical seal between radiator and A/C condensor on either side (not sure if that is normal or not). No accumulation of stuff between the A/C condensor and radiator. Lower spoiler is in place. I plan to pull the radiator and take it to the local radiator shop and have it checked out. It looks original and has what looks like JB Weld on the bottom of the right tank. Temp gauge looks like it works good based on when the thermostate opens. There are no modifications or after market parts except for true dual exhaust. Timing has been set but I think the tiiming chain may be streched a little (124 K miles on the Vette). Carb is original so I think the jets are correct, but I can not rule out running lean.

 

I will double check my seals around the radiator and confirm the spring in the lower hose as soon as I can (weekend probably). As far as what mix I'm running? Water.....with 1 bottle of wetter water (improves cooling). I put a new water pump on about 1 year or more ago. I'm running ceramic coated headers to help reduce some of the heating and my lower air dam (some call it a spolier) is fairly new as well. Maybe I need to pull the radiator and get it serviced!? Thanks to everyone who chimed in.....

 

My 71 never goes high because of speed. The radiator was recored last summer and all of the seals were replaced around the support. If your radiator and seals are good (JB weld on the tank probably means no) then check the fan clutch and blades possibly reducing flow at high speeds (if the clutch isn't disengaged the blades will oppose flow).

 

Tom DeWitts aluminum replace direct fit radiator.

My BB with a good copper/brass ran 210 hwy, 200 city - would overheat with AC running even on the hwy.

Did the radiator thing ... 180 on the dime all day long, 200 with AC

my 2 cents ...

Bill

 

Yep, I got a rad and duel spal fans from him. My car stays nice and cool at all times.

 

New Radiator, Shroud, Fan Clutch, All new seals, and New spoiler. Temp is exactly whatever thermostat I have installed then 10 degrees higher with A/C.

 

I did a complete cooling system revamp that ended up with a new radiator after CI-V . With the new rad, hoses , fan clutch and a 165 stat, it never gets above 170 no matter how hard I push it. I am going to bump the stat up just a bit when I re-do the heads next spring...

 

I replaced all the items that you have and I still am over 200 at highway speeds. What else did you do? I just ordered a new spoiler on eBay and I am hoping that will help out. Ideas?....

 

I forgot to mention I am also running a flex fan. It seems to move a massive amount of air. I think it may be time to pull the radiator and make a trip to see the radiator dude.....

 

Also check the inner wheel well liners at the front, I had one damaged (1/2 missing) and that dumped a lot of the air around the radiator. The engine ran cooler once I repaired the liner.

An internal combustion engine is a "heat engine" the more fuel you dump in, the hotter it gets.

 

If anyone would have a heating problem is should be me with the big 8-71 blower. I can run without any fans as long as I am moving regardless of speed.
I did alot of thermostat in, thermstat out, day after day changeing it in and out. I found my motor runs alot cool WITHOUT a themostat. With a thermostat I need one fan all the time, without I don't need a fan. I run 2 electrics, each on seperate switches and found without worked best for me. I also have temperature sensors in both heads and after heat soaking the passengers head comes down quicker to match the drivers head, more even temp in both heads.
I run my water pump 30% above engine speed.
The lower spoiler causes it to run hotter if I take it off. I also made sure to deflect as much air as possible up from the spoiler through the rad by adding a few deflection pieces of aluminum.
I don't believe in slowing a pump down and thermostats have their place but not in my vet.
I know this thermostat thing has been debated over and over but I actually went to the trouble of testing repeatedly removing and installing and for me it worked better without.

 

Buy a book called "Air Conditioning Strategies for the 63-82 Corvette" (Eckler's 34440, $19.99). The title is misleading since it goes into great detail about how to get air through the radiator instead of around it (which is the way to stay cool). The '70s had a BUNCH of holes for air to go around instead of through the radiator, and air, like electricity, takes the easiest way through anything.

 

It has always been my understanding that temperature issues at speed are a cooling problem resulting from either insufficient cooling, as in a worn out radiator, or insufficient flow, as in a worn water pump. Temperature issues at low speed can often be the result of a bad fan clutch or missing foam seals. I cannot imagine a bad fan clutch being the culprit at speed. I always thought that you could run an engine at highway speed with the fan clutch and fan completely missing since the air flowing over the radiator should be sufficient for cooling. At least this is what I have been led to believe.

With that in mind, I had cooling issues with my 66 L79 at highway speed. The temp gauge would steadily climb as I cruised at these higher speeds. I tried a new fan clutch even though I knew it wouldn't make any difference; I tried a new thermostat and no thermostat; I ensured that the spring was in the lower radiator hose. All to no avail. I finally bought a repro Harrison radiator from DeWitt's and that solved ALL of my overheating issues. I could now cruise at 70+ mph without even breaking 190 degrees. Before I could only cruise at 70 for a few minutes without watching the temp gauge climb.

If you think about it, all that you are doing by using the additives like Water Wetter, electric fans, etc, is putting a band aid on this overheating issue. This subject gets discussed here and on the NCRS discussion board regularly. But you know that GM built these cars to run on the street and when they were new very few people had overheating issues. I remember living in Colorado and the guys with BB's and a/c could cruise in the high temperatures in the mountains and never have overheating. Find the source of your overheating, cure it by replacing the faulty components and stay away from all of the band aid approaches.

Just my $.02.
Gary