cooling issues 66 coupe with air

[Mark U.]

it was hot yesterday and i put on the ac and drove it around 100 miles city and highway,the temp went to 230 maybe a little above.I do not know what kind of radiator in there but it has a 3 inch core-also 160 t-stat fresh anti freeze.I did check it has a 6 blade fan and thermostatic clutch for the fan,the fan when hot did not seem to blow air back towards the engine i would have thought it would blow the air back toward the engine. i have on order a new clutch for the fan,any others have a similar problem?

Thanks Mark

[Jack H.]

Re: cooling issues 66 coupe with air

First, do you trust the temp gauge to be reporting coolant temp accurately? A second opinion with an IR thermometer can verify. You don't want to be fighting a 'ghost' problem!

Second, my rule of thumb is A/C engaged should raise coolant temp by, maybe, 10F, over non-A/C driving. So, there's a hueristic you can play with.

Third, it sounds like 'Bubba' has worked on your car car... The factory original configuration was A/C equipped cars in '66 used a 5-blade fan (not six). The A/C version of the fan was slightly larger (18" diameter) compared to the non-A/C fan and the blades may have had a slightly more aggressive pitch. But, it's VERY difficult to eyeball a blade pitch differential of 2-4 degrees...

Last, the fan clutch, while appearing to be a rather simple critter, is actually pretty complex. It's performance profile is a 3-dimensional plane with %-slip being the target axis and ambient temperature + engine RPM being the independent controlling axes.

When HOT, as you described, the temperature axis should dominate and the fan's %-slip (difference between RPM of the input shaft and actual RPM of the attached fan) should approximate 0% (virtually locked rigid). So, if you noticed very little air flow from the backside of the fan, you're probably onto something in thinking there's a fan clutch performance issue.

BUT, in my experience, these 'hot car' issues typically involve MORE than just one thing. You need the radiator to be working to spec, the A/C condensor to be mounted properly and in good repair, the cooling system to be properly sealed and pressurized, the correct fan for the application, a properly functioning fan clutch and the appropriate factory original air dam components to guide air through the radiator & A/C condensor appropriately.

[Wayne P.]

Re: cooling issues 66 coupe with air

My temp also runs hot when in traffic. I was told to put a electric fan inside the shroud . I think I will do it over the winter . I just have to find one that fits. Hope you can resolve heat problem. Sounds like a good day for a drive.

[Mark U.]

Re: cooling issues 66 coupe with air

I am starting with a t-stat-clutch for the fan-quart of stay cool for the rad-also took off the intake and am going to plug up the exhaust holes under the carb to keep as much heat away from the carb. New belts and put it all back together and see what happens.

when i drovre this car yesterday when the car temp went up to 230 the car started to run poorly so it would be a good indacation it was hot.


also 160 t-stat or 180 i had a 160 in and am thinking about going to a 180

[John H.]

Re: cooling issues 66 coupe with air

also 160 t-stat or 180 i had a 160 in and am thinking about going to a 180

Mark -

Put a 180 in it - that's what it came with. The thermostat has nothing to do with maximum operating temperature - it only controls the MINIMUM operating temperature. You might find this article on Corvette Cooling useful:

http://www.lbfun.com/warehouse/tech_...em/cooling.pdf

[Clark K.]

Re: cooling issues 66 coupe with air

Mark,
A 1966 Sting Ray with C60 (factory A/C) should have a 5-bladed fan, part #3789562 or the alternate #3863137. This is according to Noland Adams' book "...Vol. 2" (page 340).

This is different than the '64-'65 fan, which was 7-bladed and had a unique profile. -Clark

[Clark K.]

Re: cooling issues 66 coupe with air

Now for the issue of "she's too hot, she's not happy". You did not specify which engine you have in your '66 coupe.

I have a '65 coupe with the L76 engine and C60. I dare not use the A/C on a hot day (over 85) or in stop and go traffic. The temperature keeps climbing until I shut off the A/C and turn on the heater! I am not willing to take a chance of damaging a low-mileage original engine.

I have checked the temps with an IR "gun" (gauge is correct) and changed out the fan clutch, radiator, thermostat, coolant, expansion tank cap, set and reset the timing, installed richer jets, etc. all to no avail. The only two things I have not done is open up the engine or replace the water pump. Many experts tell me that certain engines with A/C will NOT stay at the thermostat rating. My quest for usable A/C in my car continues. Good luck with your journey. -Clark

[Mark U.]

Re: cooling issues 66 coupe with air

i have a A.I.R. 327-300 horse engine with a powerglide trans

[Duke W.]

Re: cooling issues 66 coupe with air

The '66-'67 PG/AIR combination has a severely retarded spark advance map below about 2000 revs, which causes hot running in low speed traffic. You should map the centrifugal advance to see if it is still OE (see you CSM or AMA specs), and I recommend modifying it to the non-AIR centrifugal curve and initial timing and convert the ported to full time vacuum advance.

However, 230F is within the range of normal operating temperature. With a 50/50 water antifreeze blend and a 15 psi cap, the boilover temp is about 265, so even at 230 you have over 30 degrees margin.

Most replacement fan clutches are calibrated for the later 195 degree thermostats, so the clutch tightens at a higher radiator outlet air temperature than most OE C-2 fan clutches, however, your car may have originally had a 195 stat and a fan clutch that tightens at a higher radiator outlet temp than non-emission controlled engines of the era. Again, check the specs.

Duke

[Gary J.]

Re: cooling issues 66 coupe with air

If you have your owners manual it will tell you what t-stat you should have in your car. Should be listed in the very back of the manual. I think for a BB it is 195 degree, I may be wrong, its been a while since I have looked.