Cooling cliche

[myk]

So how does the old saying go?  If you're overheating at speed, it's a coolant flow problem, but if you're overheating at idle it's an airflow problem?  Did I get that right?

Charger's been running hotter lately, like 230* in traffic hotter, and I thought it was because of my new initial timing number of 24*.  I dialed it back to 18* initial and it helped, but it's just taking longer to get to 230*.  At speed the car can maintain 180* on the hottest days.  I've searched and studied as much as I could about an airflow problem and since I have a fan shroud I figured my fan clutch, which has been on the car for the 20 years that I've owned it, can be the only other problem.  I've also learned that there is no reliable way to test a fan clutch, and the FSM even states to just "replace it with a known good unit."  I bought the Hayden 2765 that everyone's talked about and mounted it today.  I have to say I don't like the bolts riding on the outside of the mounting flange but it seems tight enough.  Man, those bolts were tricky and thank God for small hands.  I should've listened to A383Wing about the studs and nuts but I'm the type to try and ice skate uphill.  Questions:

*How is it that all of the "correct" clutches bury themselves into the radiator by being too long?  I am running a stock spec sized 26" radiator, but I can see that many others on here have had the same problem.

*I want to verify the proper "behaviors" of a thermostatic clutch fan so I'll know what to look for when testing this thing.  So, the fan is supposed to be "freewheeling" until the engine 'temps make the clutch lock up?  And then disengage when it is appropriate to do so?  Is the fan supposed to turn at all when the engine is cold?  Because with my old fan clutch the fan always turned no matter the 'temps. 

*Is there anything else that could be causing the low speed over-heating?  Again it's my understanding that low speed overheating is an airflow problem, but someone please correct me if I'm wrong.  

Additionally, I have a new aluminum radiator and a Milidon high-flow water pump and t-stat ready to go in.  I hope that cooling will be one less thing to think about after all is said and done.  Thanks for any input...

[cdr]

from haydens page,  https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CB4QFjAAahUKEwjd46max5rIAhWDS5IKHajABH8&url=http%3A%2F%2Fwww.haydenauto.com%2Ffeatured%2520products-fan%2520clutches%2520and%2520fan%2520blades%2Fcontent.aspx&usg=AFQjCNHdtePzCXzTFgpcCnqp-HT2Eqkt9Q

[cdr]

hot running in traffic is normally an air flow problem, not always, but is the most common problem.

[myk]

Thanks 'CD.  Hopefully this new clutch will solve the problem, although now I think the fan sits too far back from the shroud.  Guess the new, fat aluminum 'rad will help out in that department...

[c00nhunterjoe]

The distance from the rad makes no difference as long as the fan is within the shroud
Simple check for airflow is a peice of cardboard in front of the rad. The fan should be able to hold it against the rad at idle.

Is your current rad a 2 row or 3 row? My mild 383 would get up to 200 on summer days in traffic with a 2 row. Swapped to a stock 3 row and it will idle all day at 180

[myk]

Current 'rad is a 2 row parts store piece.  Like the clutch, the 'rad came with the car many moons ago...

[c00nhunterjoe]

Nothing wrong with a parts store radiator. I would venture to say you need more capacity for your given airflow. If you already have the aluminum one on hand, put it in. Night and day difference.

[Dino]

Had my temps go up about 30 degrees a while back, and it would do it real quick as well.  Turned out to be a tiny leak on the bottom hose at the waterpump.  Tightened the clamp and temps went back down to normal.  Might want to check the system for any leaks, no matter how small.

[c00nhunterjoe]

And proper level. Add an overflow bottle if you havnt already, and keep the radiator full. If you only have the drain hose on and run the rad a few inches down, it will run hotter.

[1974dodgecharger]

had a 2 row 22inch rad with no shroud and I was good in AZ got up to 210 in very hot days sitting there and driving on highway 190 also.

check the fan if you can turn it by hand pretty easy the clutch is shot and if it has resistance then your good that's how I was told to test it.  Also you can sit there wihle you turn the car on and let it reach up to your clutches temp, 'kick' and feel the fan move more air.

I switched to electric myk and to be honest I like it better than mechanical......just me.

[justcruisin]

The 2765 hayden is a medium duty clutch, not ideal, especially with high pitched fans. The only reason to use it is if you have a clearance issue. The HD version has more surface area for drive but it does put the clutch a further 5/8" closer to the radiator. Depending on the amount of cooling you need the 2765 may work for you. A spacing ring can be fabbed up to help with the bolt circle.

[myk]

Had my temps go up about 30 degrees a while back, and it would do it real quick as well.  Turned out to be a tiny leak on the bottom hose at the waterpump.  Tightened the clamp and temps went back down to normal.  Might want to check the system for any leaks, no matter how small.

Yeah about that.  I went outside a few days ago and there was a small puddle of coolant under the motor.  I didn't find any loose hoses so I figured my 12 year old Eddy pump had finally bitten the bullet.  The coolant recovery bottle was properly hooked up and not leaking either. 

As for the jaguar clutch, I didn't want to run it either but...like I said earlier all of the "correct" clutches bury themselves into my radiator. 

I dreamed of having an electric fan and water pump set up but honestly, I just don't trust electronic accessories enough to run them in the Charger.  I'm still recovering from the electric fuel pump nonsense and I need this car to be daily driver reliable.  Thanks for all of the feedback guys.  I'm going to run the car for the last big cruise of the year this week and hope the clutch is the issue after all...

[1974dodgecharger]

I don't like electric water pumps either im kinda scared  electric fans on the other hand I trust......

[bill440rt]

The tiny 2-row radiator is definitely a culprit. As mentioned put that aluminum rad in there & watch your temps decrease.  

A few words about fan clutches. Tony's Parts has been reproducing the correct BB fan clutch for non-A/C cars for quite a while now. This has the shorter shaft, & is a correct repro. Scroll down about 1/4 page:
http://www.tonysparts.com/newproductsB.htm

Cars with the heavy duty cooling package (typically those with A/C), used a fan clutch with the spring on the front. Part# is 2658456. They are really hard to find too, hence the use of the Hayden clutch. I don't trust the smaller hub face on the Hayden, either.
A correct "parts store" replacement clutch was the Eaton FC-28, which is exactly like the "456" clutch. Both of these have the correct shorter shaft to place the fan correctly in the shroud. Not as hard to find, they do turn up time to time on eBay and such.
Mopar's clutch in their viscous fan package is similar, with a slightly longer shaft. This could be tricky on cars with a thicker radiator. It fits on my '68 with a 3-row. It is close (maybe 1/2" away or so?), but it does fit. I've since located a FC-28, which I'll be swapping in soon.

[HPP]

The cliche is generally correct. Its not 100%, but in general, yes.

I haven't had any issues with interference, but then again I mostly deal with small blocks, so a big block may present different issues.

When you say a clutch fan "freewheels" I'd say it depends on how and what you mean by freewheel and the type of clutch. If you can spin it easily by hand and watch it go round and round with one spin, then your clutch is shot. You can turn them by hand, but you should be able to feel resistance and it should not spin freely at all. The best thermostatic clutch fans will engage/disengage not just with air flow but also air temp. There should be some resistance felt when the engine is off. They should briefly engage at start up until the fluid is warmed and displaced, and then they should disengage and engage with a specific temp range. Now, when they disengage, it does not mean they stop spinning altogether. What happens is they will turn 50% of engine speed, but will still turn. They just are slipping. Once the temp reaches its threshold limit, then it locks up and move at engine speed. When you shut down the warm engine, it will be easier to turn by hand because of the displaced fluid and warm temps.

If you have a shroud, you want the fan half in and half out if at all possible.

One thing many people overlook is pulley ratios. If you have mixed and matched and altered pulleys or installed overdrive pulleys, you have changed the ratio and opened up the potential for overheating. If you overheating is suddenly occurring, then it likely isn't  this, but I mention it for others following the thread.

[myk]

Bill thanks for the link to Tony's parts but, oi vey; that's a lot of scratch for a clutch. 

I think I now understand about the fans and how they should be spinning.  Over the years I've never noticed the fan increasing in speed or slowing down.  Maybe my clutch has been defective all of this time?  Someone suggested that I mark one of the blades and time it with a timing light. 

You're right about the pulleys though; this was originally an AC car but I ripped it out and recall changing something; I don't recall what exactly but a pulley or two did change, for sure.  I'm going to test the car with just the clutch changed.  When the car heats up I'll try to see any leaks that I don't see now...

[John_Kunkel]

A veteran mechanic friend of mine proved to me that the clutch fan can affect temps at road speed...depends on the car.

[HPP]

The Tony's clutch is for die hard, gotta be original and have the right stampings crowd. There are less expensive ways to get the same thing.

Its hard to see the change in spinning on the fan, but if you have a quiet exhaust, you certainly can hear it. It will almost sound like an electric fan turning on as it locks up. if you clutch is locked up and spinning full on all the time, I'd think you wouldn't have overheating problems. Now if it was running 50% of capacity, and is further slipping and loosing efficiency, then you might notice the temp climbing more.

Similar thing with pulleys. If your ratio was outta of whack way back when you changed them, you would have noticed then. It wouldn't be creeping up now.

[myk]

A veteran mechanic friend of mine proved to me that the clutch fan can affect temps at road speed...depends on the car.

I think I can see that....sort of.

Its hard to see the change in spinning on the fan, but if you have a quiet exhaust, you certainly can hear it. It will almost sound like an electric fan turning on as it locks up. if you clutch is locked up and spinning full on all the time, I'd think you wouldn't have overheating problems. Now if it was running 50% of capacity, and is further slipping and loosing efficiency, then you might notice the temp climbing more.

Similar thing with pulleys. If your ratio was outta of whack way back when you changed them, you would have noticed then. It wouldn't be creeping up now.

Maybe before the headers I could've heard the fan but not now.  Actually, even before the headers I don't ever remember hearing the fan lock up as you describe but the car has always been loud to me anyway.

In any case, after making sure the Hayden clutch was on securely I drove the car out for a bit and just parked and left it running for about a half hour.  Temps slowly creeped up and topped off at 220*, which isn't where I want it but at least it isn't 230+ any more.  I did not run the pusher fan up front to help the clutch fan.  No leaks were spotted during the cool down period afterward, which still leaves me wondering about the puddle of coolant I found underneath the car a few days ago.  

Just how does the water pump weep hole behave when it's starting to go, anyway?  On my '99 Bird I lost the water pump just minutes after the weep hole started to leak...

[68CoronetRT]

I just went down this road and here's what I came up with.

3 row aluminum Champion radiator, custom build shroud and Hayden Jag clutch keeps the engine at 180 while in the garage, when it was 95 degrees here last week with like 90% humidity(This is SD.... WTF is up with this weather?). The shroud IMO is key.

[myk]

Yeah I got all that.  We'll see what happens when the Milidon water pump and aluminum radiator with 1" tubes x 2 goes in...

[68CoronetRT]

Yea, I'm running the Milodan WP and T stat as well.

[bill440rt]

From what I understand yeah Tony's clutch is dead-on visually, but still has no numbers or stampings. So from a fitment standpoint of short shaft clutches yeah it's the most correct and no worries from the smaller mount hub.
If you're looking for sticker shock go price an original. 

Myk, if the Hayden clutch does not work for you check the measurement from the water pump hub face to the radiator. If you have enough clearance then the MP 4095704 clutch may be your ticket. It has a slightly longer stem, but it works very well.
You'll still notice a big difference with the aluminum radiator. My '69 with the aluminum Griffin and electric fan setup runs very cool. Hottest it ever got was 190* with the A/C on, this was on a very hot summer day around 105*. 

[A383Wing]

Yeah I got all that.  We'll see what happens when the Milidon water pump and aluminum radiator with 1" tubes x 2 goes in...

there was an extensive test done on water pumps here, and the Milidon from what I remember didn't cut it...stick with a stock pump, but you don't listen to me anyway   

[firefighter3931]

there was an extensive test done on water pumps here, and the Milidon from what I remember didn't cut it...stick with a stock pump, but you don't listen to me anyway   

That hasn't been my experience. Over the years I've used a half dozen of those pumps in various builds and never had an issue. The Milidon HV pump works like a champ and takes a beating....some have seen 7000rpm at the strip and didn't blink. The anti cavitation plate is a huge bonus....nice improvement vs a stock pump.


Ron