[oldman66gto]

Hi, Hopefully I can get some recommendations, or guidance.
Some background information:

The engine temperature is getting too hot.
I live in St. Augustine Fl, and temps are getting into low 90's, & at least around low to mid 80's.

'66 GTO , 428, 4bbl, 4spd, Vintage Air a/c, 3:55 rear. Radiator was replaced about a year ago. Flow-Kooler water pump installed, Hayden fan clutch installed 4/24. Looks to be a new 6 blade fan. Fan is 2" from radiator, and has a complete shroud around it. It has a 180 degree thermostat. No coolant leaks.
Also, is there an upper radiator hose bracket available to support the top hose? The bottom of it is about 2"-2 1/2" above the top of the power steering pump.

The issue is that when driving at 40 mph, the temp will creep up to about 200.
If I stop, within 2-3 minutes, temp will go 220-230. If I drive it 3-4 miles, temp will return to 180-190. All of this is with the a/c running, which is needed here in Florida.

Hopefully I've provided enough information for some advice or suggestions.

Thanks,
Allan

[mgarblik]

Generally, temperature creep while sitting, idling, is insufficient air flow through the radiator. Are you SURE the fan clutch is working properly? It should be noticeably noisy, like a wind tunnel, when the fan clutch is "clutching up" when hot. At 200 degrees and hotter, the clutch should be running at engine speed. Put your hand behind the fan, engine side with it running hot. You should feel a tremendous amount of air being pulled through the radiator. Possibly the fan that is installed on the clutch is not made with the proper pitch. (possible, but unlikely). Do you have the proper size pulley on the water pump? Possibly they are not turning fast enough at low RPM's for the AC system and pulling enough air past the condenser and through the radiator. I would start in these areas.

One thing I would caution you on would be to jump immediately to an electric fan system to fix this problem. In working on these cars for decades, I rarely find ANY electric fan system, single fan, dual fan, push or pull style that will out cool a proper clutch fan system. Good luck with it.

[78w72]

You said the fan is 2" from radiator with shroud completely around it?

Im not familiar with older GTO's but on most other cars and 2nd gen firebirds, the fan isnt that close to the rad, more like ~6" away & the fan should be part way out of the shroud, about half way in with part of the blades exposed. If the fan isnt positioned right in/out of shroud it wont pull air as designed.

Also read the flow kooler pumps arent as good on pontiacs as a good quality pump with cast impeller since they have a sheet metal ring welded to cut down impellers, consider getting a good OEM type pump, I use aluminum pumps with full impellers clearanced
tight to the plate.

What radiator? If you dont have one, maybe a good aluminum radiator would be a good idea to help with temps?

[nUcLeArEnVoY]

200 is nowhere near overheating, and in SoFlo during the summer, I'd say you're doing pretty well. As for while idling, as people have been stating: temp creep at idle is usually an airflow issue, but coolant flow also plays a role. I run a flowkooler as well and it's been fine for me, but honestly I don't think it performs any better or worse than a stock cast impeller so I probably spent extra $$$ for nothing. The vane design on mine is probably different from your's, too, as I'm assuming you're using an 8-bolt bump vs. the 11-bolt I'm using.

But another factor with coolant flow other than the water pump design is also the pulley, which plays not only a role with how fast the pump spins, but also the fan. Make sure you're using an overdriven (i.e. smaller diameter) water pump pulley when you're running AC. The factory usually did this with AC-equipped cars due to the additional load the AC puts not only on the engine, but also the additional load the condenser puts on the radiator.

Idle temps are also affected by ignition timing. Any street motor should be using vacuum advance, and for a '66, those were usually hooked to manifold vacuum which is ideal in this case. Higher ignition timing will help an engine run cooler at idle speeds, so you may want to consider looking into that as well.

Your best bet is to just research the stock configuration for your car and engine as far as the fan and orientation goes. A fan that is positioned too close to the radiator will pull air only from the area directly in front of the fan - you move the fan back a little more and correctly positioned in a shroud, it will funnel air throughout the entire radiator as it should. This principle works well with 2nd gen radiators as 78w72 stated above.

South Florida will really put a cooling system to the test. I live in Miami-Dade county and I usually drive my T/A in the mornings and evenings so I don't need to use the A/C, since while my A/C does work and blow cool air, it strains the motor a lot and the engine temperature climbs very fast while I'm using it. May be something wrong with the compressor or an insufficient charge stressing the system. I've never bothered looking into it, since if I'm not running AC, my car conversely has trouble REACHING operating temperature after totally overhauling my cooling system.

[Goatracer1]

You are probably chasing a problem that does not exist. If you have a 15 psi radiator cap the boiling point of straight water is about 250 degrees F. If you have a 50% mix of water and antifreeze it is even higher. About 265 degrees I think.

[78w72]

Originally Posted by oldman66gto

Fan is 2" from radiator, and has a complete shroud around it.

Originally Posted by 78w72

You said the fan is 2" from radiator with shroud completely around it?

Im not familiar with older GTO's but on most other cars and 2nd gen firebirds, the fan isnt that close to the rad, more like ~6" away & the fan should be part way out of the shroud, about half way in with part of the blades exposed. If the fan isnt positioned right in/out of shroud it wont pull air as designed.

??

[Formulabruce]

Lets see a pic of that upper radiator hose.

[68 Firebird]

how is your ignition timing
my 68 firebird 400 is sensitive to timing and engine temperature

Gerry

[dataway]

A picture of the fan/shroud setup is very valuable when diagnosing air flow issues.

You also want to make sure any baffles/flaps/covers used in the OEM AC optioned cars are being used to prevent hot engine compartment air from recirculating through the radiator.