Over Heating issue

[Whons]

I don't know a lot about clutch fans. I'm sure all the advise that has been given to you is correct. Try a simple thing . when the engine gets up to operating temp. try to squeeze the upper radiator hose. it should feel firm. if you can squeeze it the system is not holding pressure. put a new radiator cap on. I've had that type of problem in the past on many sbc engines. You might even see a permanent impression in the rubber gasket on the old cap.

[Whons]

If my memory is correct, for each lb of pressure you raise the boiling point by 3 degrees.

[TheBMan]

On 4/15/2023 at 9:34 PM, MC1of80 said:

IF you have the type fan clutch like the one pictured in the 396.com add, you take a screwdriver or needle nose pliers and take the end of the spring where it is anchored on the outside and wind it tighter by 1 TURN and reanchor it. The fan clutch works way better. 

I have found IF using the "thermo" coupler type and you race the car or drive spiritedly they have a tendency to internally overheat quickly and freewheel rendering it useless. 

I have this type of fan clutch. I get to about 1/4 turn and it gets very stiff. I can't imagine trying to get one full turn out of it, I can't even get 1/2. 

[MC1of80]

7 minutes ago, TheBMan said:

I have this type of fan clutch. I get to about 1/4 turn and it gets very stiff. I can't imagine trying to get one full turn out of it, I can't even get 1/2. 

It can be done. If you don't feel comfortable, try 1/2. 

7 blade fan and HD clutch will make a difference. 

[TheBMan]

1 minute ago, MC1of80 said:

It can be done. If you don't feel comfortable, try 1/2. 

7 blade fan and HD clutch will make a difference. 

This is the actual fan and clutch I've been running; I took it off to tighten the spring because the temp creeps up in traffic (has gotten up to 210°). I'm running a 180° t-stat, new 3-row radiator and 50/50 pre-mix coolant. If you're saying that it's supposed to be hard to turn the spring, I'll go for it.

The clutch seems to be operating normally with good resistance (not freewheeling).

[MC1of80]

No guarantees but give it a 1/2 turn more on the spring. 210 in traffic is not horrible as long as when traffic starts moving, the temp goes down. 

What type and how old is the radiator? 

[TheBMan]

I just put 1/2 turn on it and reinstalled. Getting ready to go for a test drive now. It's about 80° here today. It does go back down to 190 when moving. It's a brass 3-row reproduction replacement. Picture of the setup attached.

[TheBMan]

It got up to almost 220 while sitting in traffic. It didn't feel like it was pulling a lot of air through the shroud so I tried to stop the fan with some cardboard and it would not stop. Still not convinced it's fully engaged.

[TheBMan]

On 4/23/2023 at 7:52 AM, Whons said:

I don't know a lot about clutch fans. I'm sure all the advise that has been given to you is correct. Try a simple thing . when the engine gets up to operating temp. try to squeeze the upper radiator hose. it should feel firm. if you can squeeze it the system is not holding pressure. put a new radiator cap on. I've had that type of problem in the past on many sbc engines. You might even see a permanent impression in the rubber gasket on the old cap.

Oh yes, the system definitely builds and holds pressure. The hoses get very firm. I have a 16lb cap, which should be correct for this car.

[420ponies]

So, Have you drilled the .062" hole in the base of the Thermostat? I'm just wondering if it has air in the system. I ways use a 20 deg. less thermostat as to where I want it to run down the road.

[Blake350]

usually the fan clutch is super stiff (can hardly turn by hand)   the one in my chevy van was 'freewheeling'   and was shot....new one very tight

[TheBMan]

2 hours ago, Blake350 said:

usually the fan clutch is super stiff (can hardly turn by hand)   the one in my chevy van was 'freewheeling'   and was shot....new one very tight

Oh yes, mine is super stiff. I have a new Hayden HD unit. Appears to be working as it should. Thanks!!

[TheBMan]

On 6/4/2023 at 8:39 AM, 420ponies said:

So, Have you drilled the .062" hole in the base of the Thermostat? I'm just wondering if it has air in the system. I ways use a 20 deg. less thermostat as to where I want it to run down the road.

Yes, I did drill a small hole in the thermostat. 3/32". I'm very certain it has no air in the system. Thanks!!

[420ponies]

I am thinking you should try a 160 degree thermostat in this set up .I had done this same thing on mine and it ran around 200 no matter what the atmospheric temperature was. Your radiator is a 3 core style, correct? I was just looking at the last picture of the upgrades and noticed that the fan in not inside the shroud all the way. Blade should be Flush at Shroud. You might need a spacer to get it inside and flush with the shroud. That provides a better draw of air at the radiator.

[MC1of80]

2 hours ago, 420ponies said:

I am thinking you should try a 160 degree thermostat in this set up .I had done this same thing on mine and it ran around 200 no matter what the atmospheric temperature was. Your radiator is a 3 core style, correct? I was just looking at the last picture of the upgrades and noticed that the fan in not inside the shroud all the way. Blade should be Flush at Shroud. You might need a spacer to get it inside and flush with the shroud. That provides a better draw of air at the radiator.

Believe it or not, his fan is sitting correctly. Half in/half out of the shroud is correct. All 5 of our Monte Carlos, big and small blocks, stock and modified all are the same. 

If yours is all in, it will work also. If all outside the shroud, no bueno. 

[John S]

I know this may go against conventional wisdom. I have a 350 300 hp with the small radiator. The radiator top cover has three bolts. I bought a seven blade fan put a fan clutch on it but I used the centrifugal fan clutch, I also had the radiator core changed to a 3 row core. I live down in Georgia, it gets hot in the summertime. The temperature does not rise when sitting in traffic. This type of fan clutch from what I understand, is  supposed to lock up at idle to bring more air in through the radiator and free wheel at high rpm. Ever since I made those changes I have had no problems. Again, I do not do as much work, or probably have as much knowledge as a number of people on this forum. All I can tell you is what worked for me.

John S

[TheBMan]

12 hours ago, John S said:

I know this may go against conventional wisdom. I have a 350 300 hp with the small radiator. The radiator top cover has three bolts. I bought a seven blade fan put a fan clutch on it but I used the centrifugal fan clutch, I also had the radiator core changed to a 3 row core. I live down in Georgia, it gets hot in the summertime. The temperature does not rise when sitting in traffic. This type of fan clutch from what I understand, is  supposed to lock up at idle to bring more air in through the radiator and free wheel at high rpm. Ever since I made those changes I have had no problems. Again, I do not do as much work, or probably have as much knowledge as a number of people on this forum. All I can tell you is what worked for me.

John S

I've wondered if it was worth trying the centrifugal clutch. I've gone through everything else (twice). There really is no logical reason for this engine to get hot. I'm considering going to a 4-row radiator but that's a $1000 proposition with no promise that it will solve the problem. My only concern with the non-thermal fan is that it might be loud at idle. @John S, can you speak to that?

[John S]

1 hour ago, TheBMan said:

I've wondered if it was worth trying the centrifugal clutch. I've gone through everything else (twice). There really is no logical reason for this engine to get hot. I'm considering going to a 4-row radiator but that's a $1000 proposition with no promise that it will solve the problem. My only concern with the non-thermal fan is that it might be loud at idle. @John S, can you speak to that?

It doesn’t sound loud to me. Originally I had that fixed four blade fan on there since I do not have air-conditioning but I do not notice any excessive noise.

[TheBMan]

20 minutes ago, John S said:

It doesn’t sound loud to me. Originally I had that fixed four blade fan on there since I do not have air-conditioning but I do not notice any excessive noise.

Thanks John. I ordered one and will update here after I get it installed. 

[John S]

I hope it works for you. It made a difference for me.

[TheBMan]

Update on this... I've tried both types of clutches for the fan (centrifugal and thermostatic) with similar results: temperature creeps up slowly at idle when warm outside (doesn't have to be hot). I sent a tech question to Hayden via their website and surprisingly one of their support people called me the same day (wasn't expecting that!). He explained that these clutches fully engage when the *air* temp across the coil spring sensor on the clutch reaches 170° to 180° not when the engine temperature gets to any certain number. I knew this and it makes sense but thought I would reiterate in case anyone didn't know. Anyhow, he suggested trying the severe duty clutch, which I did, but it performed the same. Turns out that the difference between severe duty and heavy duty is the depth and number of cooling fins on the clutch assembly. Technically they both engage the same amount (80-90% of engine speed) move the same amount of air.

I have a new three-row heavy duty copper/brass radiator and the engine is relatively fresh so I'm sure I have no obstructions. I've tried multiple thermostats. I may go to a four-row copper/brass radiator but that's a $1050 proposition with no guarantee that it will make a difference (although technically it should). If I do that, I'll update here and let you know. I'm aware that there are aluminum options as well but I'm trying to keep the car as original as possible.

copy: @John S

[John S]

7 hours ago, TheBMan said:

Update on this... I've tried both types of clutches for the fan (centrifugal and thermostatic) with similar results: temperature creeps up slowly at idle when warm outside (doesn't have to be hot). I sent a tech question to Hayden via their website and surprisingly one of their support people called me the same day (wasn't expecting that!). He explained that these clutches fully engage when the *air* temp across the coil spring sensor on the clutch reaches 170° to 180° not when the engine temperature gets to any certain number. I knew this and it makes sense but thought I would reiterate in case anyone didn't know. Anyhow, he suggested trying the severe duty clutch, which I did, but it performed the same. Turns out that the difference between severe duty and heavy duty is the depth and number of cooling fins on the clutch assembly. Technically they both engage the same amount (80-90% of engine speed) move the same amount of air.

I have a new three-row heavy duty copper/brass radiator and the engine is relatively fresh so I'm sure I have no obstructions. I've tried multiple thermostats. I may go to a four-row copper/brass radiator but that's a $1050 proposition with no guarantee that it will make a difference (although technically it should). If I do that, I'll update here and let you know. I'm aware that there are aluminum options as well but I'm trying to keep the car as original as possible.

copy: @John S

Sorry to hear you’re going through this. Cooling issues can be a pain. I had them years ago on a 79Z 28 Camaro with air conditioning and a four-speed. Back Then I was younger, more ambitious and willing to tackle almost anything and I still never got it quite right. It always crept up in traffic. my Monte  has nothing on it. No air conditioning no extra parasitic loads on the engine that could very well be why I don’t have the issues you do. What I did though to verify was use a laser heat gun to check temperatures at different points on the engine and on the radiator , one thing I did notice is the temperature was always higher where the sender was between number one and number three cylinder on the head compared to the thermostat housing where it was always a little lower. 

[TheBMan]

@John S Thanks for the input. Like you, I have used a laser temp gauge to check at various points. Also like yours, mine is hotter at the cylinder head where the sending unit is than it is at the thermostat housing. I would expect this because the sending unit is much closer to the combustion chamber and exhaust exit of the cylinder head. There is generally 10° to 15° difference.

My engine has never gone over 220° because I've been able to move to get the temperature down. It seems that it should get to a certain max temperature and not get any hotter if the cooling system is working the way it's supposed to. I'm afraid that if I get stuck in traffic on a truly hot day like we get here in Central Ohio during the summer, it will overheat. I guess it bothers me the most because I can't explain it and I've gone to great lengths to put the best parts on my car while not straying from the stock setup. If I was doing all sorts of crazy hotrod stuff and deviating from the stock setup, I might be more understanding about why it's not behaving.

Thanks again for your input!

[John S]

17 hours ago, TheBMan said:

@John S Thanks for the input. Like you, I have used a laser temp gauge to check at various points. Also like yours, mine is hotter at the cylinder head where the sending unit is than it is at the thermostat housing. I would expect this because the sending unit is much closer to the combustion chamber and exhaust exit of the cylinder head. There is generally 10° to 15° difference.

My engine has never gone over 220° because I've been able to move to get the temperature down. It seems that it should get to a certain max temperature and not get any hotter if the cooling system is working the way it's supposed to. I'm afraid that if I get stuck in traffic on a truly hot day like we get here in Central Ohio during the summer, it will overheat. I guess it bothers me the most because I can't explain it and I've gone to great lengths to put the best parts on my car while not straying from the stock setup. If I was doing all sorts of crazy hotrod stuff and deviating from the stock setup, I might be more understanding about why it's not behaving.

Thanks again for your input!

I’ll try not to drag this out too long this may or may not apply to vehicles but I can tell you of an experience I had with cooling in the business I worked in. Before I retired I spent 29 years working for two natural gas pipeline companies working at compressor stations on their large engines. These engines have two separate cooling systems one is for the lubricating oil and the other is for the jacket water to cool the engine. Many years ago at one of our stations, the engines were running hot and these engines were cooled by auxiliary motors that pump water through the engines. This station always operated both cooling water pumps at the same time. One old foreman came in one day and asked them why they were running both pumps they said that’s the way it always has been.  He told them to shut off one pump and when they did, the temperatures dropped back into the normal range. Evidently what was happening is the water was flowing too fast through the engines and there was not a proper heat transfer. The reason I stated that is when I was younger back in the late 70s and early 1980s , a number of my friends who were into hot rodding, like myself seem to fall in love with these high volume and high-pressure water pumps or they would change the diameter of the water pump pulley. Kind of going back to what I refer to as More’s law, if enough is good, more is better and too much is just right. Again, I may be incorrect, and this may be the rumblings of a has been, but I do wonder if some of these aftermarket water pumps, and I do not know if you have one, do not perform the way the OEM ones do. Sorry for dragging this out for a while but that was the best way I could explain it. 

[TheBMan]

@John S I do appreciate the analogy for sure. I'm using a stock AC Delco water pump and stock pulleys. Man, I hate to think I would have to fiddle with flow rate to get things right if I'm using "stock" parts.