gr8corvette

I recently purchased a 65 coupe. It has been running very good. No poblems at all.
Today, I was idling in the driveway with the AC on. The temperature gauge starting very slowly moving towards the pegged position. I turned it off and let it cool down. There are no leaks, the antifreeze level is fine, and the fan belt has the correct amount of tension.
The overheating surprised me a lot since I have been driving it and the temp needle is always on 180 (once it is warmed up). After it cooled down, I took it on a ride and the needle stayed on 180 just like it always did previously.
After analysing what may have happened, I parked in my driveway with the engine idling, but no AC. The needle stayed on 180. I then turned on the AC and it started a very slow climb towards pegged. I turned the car off to cool.
After it cooled, I took it on the road with the AC on. On the highway, it stayed at 180 with the AC on. I then drove on the local roads. Melbourne FL is a small town so traffic is not bad. My average speed was around 45 MPH with a few stop lights. The temp needle stayed on 180. So I drove on a smaller road at 30 MPH. This time the temp needle started an even slower climb, but it did climb. As soon as I resumed a 45 MPH average speed, it went back to 180.
I took the car to my mechanic, he is booked up for now and will look at it in a couple of weeks when he can give it more attention (this was my idea as I know how to avoid the overheating and can drive any of my other vettes in the meantime). However, his guess was a sticky thermostat, partially blocked radiator, waterpump, or ??? He suggested that I might consider putting in an electric fan.
Any thoughts on a simple way for me to check the problem?
I have an electric fan on my '61 roadster, it works great. Anyone think I should just go ahead and put on the electric fan even if we find the problem and fix it?

MikeM

I don't normally do this but in your case, if your radiator is relatively new, whether it's copper or aluminum, I believe I'd go ahead and put and electric fan on your car if you don't care about originality.

If your car didn't have AC, I might suggest you do something else.

Your real problem may be a weak fan clutch.

Frankie the Fink

True - also be careful of which electric fan you buy. I had a friend recently test several during a build and the various manufacturers can have wildly varying performance regardless of what their 'hype' claims !!

gr8corvette

My priorities:
1. Safety
2. Worry free driving
3. Keeping as much as possible original
It is matching numbers and fairly original. However, if it is a choice between # 2 and #3, I would pick #2. I was hoping I could have both #2 and #3!

Is it possible for me to check the fan clutch? I can turn a wrench, but I usually have to have someone tell which nut to turn. Simple things I can do, but that is all. To be honest, I don't even know what the fan clutch looks like.

5thvet

A quick test for the fan clutch is try turning the fan with the engine cold, It should spin freely. When the engine is hot turn it off and try spinning the fan. It should have a lot of resistance if it is good in both cases. Another way is have someone rev the car up to about 3500 RPM and get right over the fan. It should be really blowing hard.

Don

Dan Hampton

Mike has a good point. In looking at the fan clutch check the following:

A good clutch should offer a certain amount of resistance when spun by hand (engine off). But if the fan spins with little resistance (more than 1 to 1-1/2 turns), the fan clutch is slipping too much.

Check for binding or the inability of the fan to turn.

You should also try to wiggle the fan blades by hand. If there is any wobble in the fan, there is a bad bearing in the fan clutch, or a worn bearing on the water pump shaft. A bad water pump bearing will usually cause the water pump to leak and/or make noise, but not always. Remove the fan clutch and see if the play is in the water pump shaft. If it feels tight (no play or wobble), replace the fan clutch.

Also, check for any leakage coming from the fan clutch.

MikeM

I think that it's next to impossible for somebody that doesn't know where the fan clutch is to inspect it and know what he is looking at. NO OFFENSE INTENDED!

After reading many threads on this and other forums about Corvette low speed overheating, the cause usually comes down to one of two things or both. An old, plugged up radiator or a replacement copper radiator and/or a worn out clutch fan.

AC cars generally seem to have more problems with running hot (for whatever reason) than non AC for a good reason.

AC cars need additional air flow provided by the fan at low or no speeds in order for the AC to put out max cold air.

There is a cost to replacing the fan clutch. There's a cost to replacing the fan clutch with an electric fan. If it turns out the fan is not the problem, part of the cost of the electric fan can be considered in improved AC performance.

Wire the electric fan to turn on/off and when the AC is on from a source keyed to either the enginer temp or the AC being on. Not just engine temp and not through the ignition switch.

I think that's a no brainer for starters.


PS. I think some fan kits allow the electric fan to be installed as a puller and leave the stock fan clutch in place. Not sure.

PSS. Another benefit of the electric fan is, if your radiator is in it's senior years, it can/might extend the useful life of it until..........................

gr8corvette

Mike: No offense taken. This forum benefits the folks like me that know nothing, but would like to learn. I appreciate all of the advice given.

I can try spinning the fan blades. I did not know that I should even try that, so I appreciate the tip.

One strange thing about the fan: I carefully put my hand directly behind the fan, as close to the fan center as I could get. I felt very little air movement. However, near the fan blade tips by the radiator shroud, there is a lot of air movement. My first thought was that someone had put the fan on backwards and it was blowing the wrong direction. However, I watched the movement direction of the blades as the engine was turned off (so I could see the direction it was moving) and then looked at the curvature of the blades. It seems to be moving the correct direction. When I get some time tomorrow, I am going to put a kleenex in front of the radiator and see if it pulls towards the radiator or blows away from the radiator or has no movement at all.

gr8corvette

Mike: Looking at the radiator for the engine and the radiator for the AC, it does not look like an electric fan would have very much impact on the AC at all.
The radiator for the AC is almost at a 35 degree angle to the engine radiator which is almost vertical. If I put an electric fan on the engine radiator, it will not cause any increase in air flow to the AC radiator.
I have not really studied radiator placement, but my memory is that usually both radiators are side by side and both vertical. Could bubba have put my AC radiator in wrong?
I don't think this would have anything to do with the overheating. If anything, it could have been done by Bubba on purpose to reduce overheating as this configuration would help the engine radiator.

toddalin

Are all of the seals in place around the shroud and do they completely seal the shroud to the radiator without any gaps? If not, start there.

6T5RUSH

gr8corvette,

Although my setup is aftermarket (Classic Auto Air), I added a Rehostat wired to the 2 electric pusher fans which came with the air conditioning kit. I can just "dial in" the temp point I want the pusher fans to kick in based on the dash temp. If she starts to creep up above 185 (which is where I have it set), the fans will kick on when I do not have the air running. Otherwise, these fans are always on when the compressor kicks in.

Here's a pic of the Rehostat. The probe can be seen just under the top radiator hose.

Just a possible addition you might consider when you go with an electric fan/fans.



Jim
In God We Trust!

MikeM

I am not well versed on AC equipped midyears at all. Others can chime in but it sounds like you might have hit the nail on the head with your assumption.

If your engine fan is working correctly, it should just about blow a baseball cap off the top of your head if you rev the engine and you're leaning behind the fan (don't stand beside it). If it doesn't, your clutch may be bad.

I don't believe in the tests offered so far to tell you if your fan clutch is good/bad, but what has been posted here is generally accepted as the way to check them. I prefer the baseball cap method!

If you do decide to go with an electric fan, you may find out your 37 amp alternator is a little too weak kneed to support that. It's easy to convert to a higher output alternator. Just change yours or go buy one.

Railroadman

To some degree, it also is the nature of the beast. In the late 1960's I was in a Corvette club and we participated in several parades carrying harvest queens on the back of the convertibles. If it was an evening event most guys were OK, but afternoons were different - the finish was usually a line of Vettes with their hoods up. I can vividly recall watching that needle creep up on my '67, and calculating the distance left to go hoping I'd make it. That was without AC, and most of the cars were only a few years old.

Cliff notes - Vettes of that era didn't like standing still or moving slowly on hot days.

Frankie the Fink

The only way I've truly felt like I could tell if a fan clutch was bad is when I saw the viscous fluid leaking out of it...otherwise I felt like I never really knew for sure.

Eliminated my clutch on the '61 and went with a spacer....I want full time 100% fan commitment to cooling my car in Florida.

And, as a previous poster noted, there is nothing new about having to turn off the A/C when idling overlong at a stop light...

Westlotorn

A properly working fan clutch should have resistance if the car is parked hot, some don't engage till the engine is at 220 so I would first check the fan clutch at a shut off temp of 220.
If you turn the fan blade with Eninge Off and the temp at 220 the clutch should have significant resistance when you turn the blade by hand. This resistance will go 100 % away with no more than two revolutions because the engine is not spinning. As you turn by hand the silicone in the clutch is pumped back into the storage tank in the fan clutch dis engaging the clutch. This is normal.
If the clutch is bad the fan blade will spin with no resistance when you check it engine off at 220.
If you see streaks of oil/silicone on the clutch it is leaking and you should replace it.
If your clutch is working at 220 and you don't like it that hot there are tips on this forum teaching you how to make it engage at a lower temp.

As Mike once said a properly working fan clutch is easy to identify, with your engine hot lift the hood and rev the engine, if the fan is engaged properly when you rev the engine you should hear the fan howl and it could blow your hat off your head.

The electric fan idea is great to make an AC car work while idleing. All new cars and trucks use them now.

One Warning, the factory OEM fan blades that come with a fan clutch equiped car are not designed to turn at full engine speed. If you use a fan clutch eliminator/spacer the OEM fan blade will be subjected to full engine speed. Over the years many of these have failed causing car damage and a couple deaths. If you go this route buy a new Fan blade designed to run at full engine RPM all the time.
Have a great weekend.

65 vette dude

C2's with A/C, even when new, were right on the border line for cooling......especially at idle in the summer. If your fan clutch has a coil spring on the front, it probably has 2 positions. They usually come set for newer cars, which are designed to engage at 210-220 degrees. If I remember correctly, looking at the front of the fan clutch, rotate the end of the spring counter-clockwise(unwind), to the second position. This will cause the fan clutch to engage at 180 degrees........makes a big difference at idle.

Lou64

Also, my dad had a '88 F-250 with a 460 and a Banks Powerpack on it when I was in high school. He bought an aftermarket fan with more blades, etc. blah blah. He stuck it on and about the third time he drove it, TA-PING...ping, ping, ping. The fan had broken two blades, throwing one through his radiator, the other rattling around the engine compartment, belt snapped, knicks all over.

He immediately called the company about the fan and they tried to say that since the truck had the Banks on it, it was a "high performance" engine and their warranty would not apply...My dad continued to pursue until he got his money back for the fan plus the pay for the new radiator. It helped that my mom worked in a law office.

kenba

You are right. C-2'S need a 180 degree fan cluch. Engine temp should be 180/200. The ones set for 220 will make the car overheat becasuse newer cars run higher temps for better burning. I can leave my 67 390/air conv. idle in 90 degree & will not get above 200 after changing to a 180 fan clutch but before after 5 stop lights it was peged.
KEN

gr8corvette

I finally finished looking at the stuff everyone suggested. Here are the results:
MikeM: The radiator is aluminum, at least it has a sticker on it that says it is a Harrison Aluminum radiator. See picture at bottom (if I posted the picture correctly!)
5thvet: With the engine cold (and off), I could freely turn the fan blades. Although they did not free spin with a slight push, a slight push was all it took to turn them. I did rev the engine and there did seem to be more wind blowing.
Dan Hampton: The fan spins by hand with little resistance even after several turns. No wobble in the blades. No leakage.
Toddalin: Seals? there are no seals around the shroud that I could see. Look at the picture below.
MikeM: It did not blow a baseball cap off my head when I rev'ed the engine using the linkages under the air cleaner, but it did blow considerable harder. Also, I tried putting a peice of paper in front of the engine radiator. It was sucked hard to the engine radiator with the engine in idle. I tried the same thing on the AC radiator, but since the AC radiator is much smaller, I only used a small peice of paper. The paper held to the AC radiator, but just barely. There is not much air flow across the AC radiator. See picture below for the slant of the AC radiator compared to the engine radiator.
Frankie the Fink: Full fan all the time sounds like a good suggestion. Will this cost much for my mechanic to pull out the fan clutch and put in a spacer? Is there a down side to this? Seems like everyone would be doing it???
Westlotorn: I let the car idle for a half hour with the hood closed. The temperature gauge never made it up to 180 (idle is around 650 to 700 RPM). When I put the AC on, the temperature gauge went past the 3/4 mark (I assume that is at least 220). See the picture below. Idle with the AC on is around 600 RPM. I turned the car off and the fan still turned by hand with little resistance!
65 Vette Dude: Is the spring you are talking about on the front center of the fan. See the blurry picture below. This is very hard to get to and can only be viewed with a mirror. What tragic consequence is a clutz like me going to get into if I try to move the end of the spring. If it jumps off, can I get it back on? Is there a particular tension or number of turns it needs to have?

Bluestripe67

I have read all the posts and most make sense, but seeing the photos makes me ask this question and make an observation. Is your A/C system aftermarket? The reason for the ? is you mention a rad in the picture, it's small, looks like a trans cooler. I think the A/C condensor is behind it. The radiator is not an aluminum. It may have a sticker, but that's all. On the right you can see where the copper side tank is attached. A DeWitts true aluminum rad will make a big difference in your engine cooling. Dennis