Tex71BB

(Not the 'Vette, but classic Chebbie - you guys are the best resource I know)

I just re-installed the A/C on my '70 396 El Camino and, not surprisingly, the car is running a bit hotter. Before A/C, it never got above 180. Now it climbs to 210 or 220, but only on the highway - around town it stays around 180-190. This is all with the stock temp gauge (which I know may not be accurate), but obviously the car is running 30-40 degrees hotter than before. I put in some Water Wetter, but couldn't tell a difference (still running 50/50 glycol, though). Is this too hot or not? If so, what do you think is causing it? Thanks!

ACECO

I find it strange that it's hotter on the highway than around town. Usually it would be the other way around due to the increased airflow when on the highway.

Have you checked your radiator hoses? I have seen cases where the bottom one will collapse at highway speed if it is soft or missing the internal spring. This of course would restrict flow and make the temp rise.

Also see:

http://forums.corvetteforum.com/showthread.php?t=859232

Good Luck!

jcswm

Does your cooling system have an overflow bottle???? the older systems that didn't have bottles the coolant was about 4 inches low when cold.... It always helped my cars to add an overflow bottle!!!
But it sounds like your radiator is clogging-up

comp

you should check it out, but if the temp IS correct it's not to bad
if you using coolant and a 15 lbs system

GrandSportC3

Water Wetter will only really help if you are running without antifreeze...
Have you tried to remove or relocate the front license plate to get more airflow at highway speeds??

biff85ta

Sounds just like what my TA did when the radiator plugged up. I put in a new one and the problem is now gone.

Tex71BB

I, too, was surprised that the temp went up on the highway, but not at lower speeds - I'm wondering if the problem (if it is a problem) is due to lean mixture or advanced timing.

I don't have an overflow, but definitely need one - this is my daily driver. Also, should definitely get a better gauge. Probably should reduce amount of glycol and try more Water Wetter.

I don't think removing the plate on this car would help any.

i885744

Remove the front license plate? Its an el camino, there's chrome bumper and the pull for the hood latch back there. I"ve got a 71 small block SS 350 with ac, just about the same setup and mine doesn't get that hot. You should have an overflow tank mounted near the passenger frame rail on the inner fender, make sure thats there and full of coolant. Mine used to overheat until i went to the el camino store and bought a factory radiator shrowd. I'm running the stock fan, and stock radiator setup, on a built motor with ac and it never hits 200, and i live in central california where 100 degrees is an average summer day. I'd check all the usual things, thermostat, hoses, overflow tank, etc.

I think i might even have an extra overflow tank for the camino somewhere in my garage, i'll take a look.

Rumpity Rump

ME: Redline suggests no more than 20% glycol with Water Wetter if you have a/c ....and no glycol if you dont have a/c. Id try going with 20% . Check your lower radiator hose by revving to 3000 rpms standing still -- the strong suction might be collapsing it. Have you got the condensor/radiator totally sealed up on all four sides well ? Did you power wash the radiator before installing the Condensor ? Did you do a good cleaning job on the cooling system including removing the block drain plugs ?? And finally, how old is the water pump --- look into a Stewart 6 impeller Pump if need be.

Dave

Ganey

No need for 50/50, reduce level. Rad. may need to be rodded out.

JB

I'm gonna offer a dissenting opinion here. My big block always runs nice and cool, right up until mid-June, when it does exactly what you describe, though not quite as hot (I get up to 210 or so). I'm cool all the time, until I get it above 65MPH on the highway. My radiator's fine, my air "scoop" under the front is in place, my shroud and all the foam are there (though the shroud and foam are fairly irrelevant at those speeds). I think it's just a matter of relatively high RPM and REALLY hot pavement a few inches underneath your radiator making the difference. I've even noticed that when I hit a strip of highway with those big concrete barriers on either side where they're doing construction, the water temp goes up a degree or two (lot of highway construction down here--it's like riding a luge course in your car between here and San Antonio).

BTW, my understanding has always been that 210 is not really all that hot for a big block, though 220 might be starting to push the envelope a bit.

JB

gkvetteuno

I had the same experience with my SB 71 Vette w/AC. During the summer on the freeway, driving above 70 mph, the temp would start to rise. Another factor in the equation is that it really gets hot here in Fla in the summer and as is well known, in Texas. I have driven this car to Bowling Green, Ky on three separate occassions in the summer, absolutely no heating problems after entering Tenn and traveling North. One of the things I know that was a bit suspect on my car was the seals between the radiator and radiator support and those between the shroud and the radiator. I had just never replaced them during the restoration. Now that I understand their importance, especially on the 71 type Corvettes, I supect they had a lot to do with the overheating problem.