I haven't gotten around to making a build thread yet, but a quick history of Dover and I is this:
Purchased 3 years ago with blown head gasket from overheating. Finished rebuilding from ground up this year in January. Everything from drivetrain to suspension, and even the interior.

Since the rebuild I have yet to break 215* via my ultragauge. My temperatures were typically as follows:
Idle: 205-210
City driving: 189-194
Highway <70: 194
Highway >70: 199-204

By the way, these numbers are while driving in the 90*+ weather we have been having for the past 4 months.

Intake air temps were usually between 130-190*

Using AC would cause a temp increase of 3-5* only during idle. It would not affect driving temps.

From research I have read that the AC fans do not kick on until about 215* as a backup to prevent overheating.

Here are my two hypotheses:
AC on, should help cool the engine compared to off
Clutch fan is worthless when driving about 70mph

What I noticed last night was that only one of my AC fans was working properly. The broken one would spin, but not fast at all. It was slow enough that I could stop it with my finger. After testing, I determined it was a bad fan and nothing else. After a trip to the junkyard to find out that a D2 AC fan is not the same size, I found a D1 fan elsewhere. After install of replacement fan and everything back together as it should be, here is what I have witnessed SO FAR:
Colder AC
Idle temp: 190*
3k rev for 5 minutes: 190*
Idle w/ AC off: 194*

I need to go for a drive and get some temps and stats as I would while driving to school and back, but so far it appears I'm already helping the situation.

I think that having the AC on, with the fans pushing extra air through the condenser and then the radiator, your temps should decrease and not increase as I have read that some do. To me, it makes logical sense.

As for my hypothesis on clutch fan being useless above 70 mph, here is why. I can't find and stats on how much air the clutch fan pulls through the opening it has. But I'm thinking it's possible that it may be less than the amount of air rushing through the front of the car when driving above 70. Why would this matter? Is it possible that the fan is creating a blockage instead of increasing flow? I think of it like this: You have one entrance into a building with two rotating doors moving at a set speed X amount of feet apart. The first door off the street is pushing people through at 2 people per second. But the next door into the lobby is only rotating at 1 person per second. Therefore a people are getting jammed up between door 1 and 2.
Relation: Airflow through grill at 70+ mph exceed airflow pulled by clutch fan, therefore causing stagnant air to sit around the radiator.

What are your thoughts?

I know this wasn't organized the best, but its hot, i'm ready to jump in a pool, and I just wanted to throw whats in my brain on to the forum. I'll update as I get more information.


I should add, I do not have a 100% stock cooling system. Most everything is the same except the overflow. I converted to a more traditional style with a fill cap and overflow bottle. See picture below.

 

Stagnant air at 70 mph? You sure you not suffering from heat stroke? Stay in the pool until tomorrow and stop smoking dandelions.

You need to read up on bimetallic thermostatically controlled viscous fan couplings. I hope your not going to school to be aeronautic engineer, they wouldn't let you pick the carpet color bud.

 

Well damn, I don't know how you were raised in Traverse City, but in GR that would be called rude.

Obviously I'm not going to school for engineering, hence why I called it a hypothesis (a supposition or proposed explanation made on the basis of limited evidence as a starting point for further investigation) meaning it was a thought that I had based on the example I gave and figured I would do more research on.

I'm simply asking if moving at 75mph produces 600 cfm through the grill/radiator, but the fan behind it is only producing 500 cfm, will that create a blockage to which only 500 cfm of air will flow through instead of the possible 600. (to clarify, I'm throwing out numbers for reference).

I understand how our fan clutch system works, I've read the RAVE (and then some) to understand heat and open/closing to increase/decrease rotation to increase/decrease air flow.... I'm not a total idiot.

 

I have no idea what any of this means. Where is the fan clutch? I know what the fan looks like, white fan, spins really fast right? Then there are two other fans that spin when the A/C is on correct?

 

You're fan is white? Mine's black, but anyway, the clutch is the metal chunk between the fan blades and the water pump pulley. It has a thermostat inside that opens and closes a valve based on physical temp. Hot = open. Which allows fluid to move within the clutch and create contact between the two halves which spins the fan faster.

And yes, also two fans up front for the AC. They will also kick on (if not already on from AC) at engine temperatures above 215 to provide additional cooling to the radiator.

 

The fan is disengaged and freewheeling at 70 (75) mph. It causes no interference with airflow through the radiator at that speed. The grill/bumper, A/C fans, condenser and fan shroud would cause more interference than the fan by a large margin. The other thing your overlooking is the cooling effect the airflow is going to have on everything behind the fan hence why an aluminum block is a good thing. The higher temps you recorded are due to the higher engine load moving a nearly 3 ton brick with high drag coefficient, all wheel drive mechanicals, greatly underpowered 4.0L through the air. Friction and not "stagnant air" is the issue. If your not running with synthetics (Amsoil) in your thirds and transfer case it's about time to give it a whirl.

If I'm not mistaken (Augusta Ga.) around 30 mph the fan clutch fluid is coalescing towards the middle of the clutch and by 45 mph it's complete and disconnected. That's with a stock OEM viscous in high ambient, high wet globe (humidity).

I was born and raised in Detroit, thick skin. You don't have a sense of humor either. Ah well.

 

Now that is news to me. The RAVE does not mention that, but I did find a few sites that support your explanations. So now you have me wondering if I'm the one with a locked fan clutch because it appears loud on both street and highway.

Thanks for the input.

 

Simple test, if the clutch is locked it won't turn independent from it's shaft when parked. You'll be rotating everything against the serp belt tension. I just had one that locked up hard, I heard it and felt it while pulling away from work. I keep spares. They only last about 30k.

 

important info on rover 1s, replace hoses, theromstat, overflow box, and serpentine pulley.
you dont know it but while your driving that pulley is freezing and then everything is going slow and causing it to run hot. At the beginning you said blown head gasket.
They dont blow if you maintain the parts. You cannot put 200,000 on the engine and think those parts will last and they are probably the originals.

 

I'm not so sure about this. I recently replaced my original fan clutch with another stock clutch. Driving this weekend on the highway I observed temps move to 195 and at that point could hear the fan engage for about 30 seconds which drove down temps to 188. It was about 95 deg ambient.

So while I previously believed the fan clutch did little or nothing at highway speeds, I now believe it does play a role.