The Car: 69GS400 4-speed ragtop, bone stock. Engine compartment: AC, PS, PB, fan clutch, 3-core radiator, seven blade fan. All components fairly new, including the thermostat, ac compressor, fan clutch, hoses. Location: Sunny, scorching hot south florida. No, not 100 degrees, but generally around 90 degrees with 400% humidity. Problem: No way in hell this car even thinks about running at less than 200 degrees. Wouldn't even consider going 80mph in the daytime, cause the damn thing would break 220 on its way to 235. I know -- I tried it. And no, it aint losing water. Question: What gives? What temp should I run at at sixty or seventy on the highway? Do these cars have naturally deficient cooling systems? I hate to go non-stock, but do I just shitcan the fan clutch and go to a direct-drive flex fan? Or do I just sell it to one of you generous sorts in the frozen north who are willing to take a problem car off my hands?:grin: -- Steve
Top 12, in no special order, except for # 1 & 2. 1. Have you verified the temperature with a second temp gauge? 2. Can you hear the fan clutch engage when you warm up the car at fast idle in your driveway? At some point, the fan will stop blowing "a fair amount" of air, and start REALLY BLOWING A HURRICANE, AND MAKING A LOUD ROARING NOISE AT THE SAME TIME. If you don't hear and feel the hurricane, the fan clutch is NOT working properly. You'll go from "yeah, yeah, yeah, there's plenty of air movin' under here, everything's fine, to HOLY CRAP! WHERE DID THE TORNADO COME FROM!. It'll be sudden and dramatic, once the engine warms up enough. 3. bugs, birds, squirrels, clogging the air passages in the condenser, which also clogs the air flow thru the radiator. 4. Missing fan shroud 5. Clogged water passages in the rad. If you pop the rad cap and there's whitish stalactites forming on the water tubes, you need the rad cleaned or replaced. 6. Timing retarded You better have something like 35 degrees at 3000 rpm, WITHOUT the vacuum advance. Then verify that the vacuum advance works. 7. Lean fuel mix 8. Overcharged A/C causing too much high side pressure. High pressure equals high temperature, and you're pre-heating the air before it goes to the engine radiator. 9. Collapsed lower rad hose. You need a lower hose with a spring/wire reinforcement to prevent water pump suction from collapsing the hose. Generally more of a problem at higher RPM. 10. Missing/defective thermostat 11. Rust clogged waterjackets in engine. 12. Defective water pump. Sheetmetal impeller rusted out, or impeller loose on the shaft. DO NOT think you'll move more air with a flex fan. DO NOT think you can remove the thermostat and get improved cooling DO NOT think some magic can full of chemical will solve all your heating problem.
You need a 4 core brass/copper or 2 core aluminum radiator. Also in Florida, I would run 100% distilled water, with a bottle of Red Line water wetter. The more A/F you run, the warmer the temps will be. Also a 160 thermostat .
Underdrive pullies (large water pump or small damper) can also cause a cooling problem, most commonly seen at idle or in traffic.
Wellllllll, now that you mention it, I was thinking that it might be the right thing for me to do to rescue you from your troubles.... My '68 would look good next to a droptop...
