97 Chevy Blazer, 4.3 Vortech.

It keeps overheating, after about 30 minutes of driving. No visible leaks anywhere and then I noticed that the fan isn't turning. My first thought was a bad temperature sensor but then I realized I had a mechanical fan, not an electric fan...lol.

Research is leading me to believe that my Fan Clutch is probably the culprit. Are there other possible culprits that I should test first?

I've already purchased a used OEM Fan Clutch, rented the specialty tool and purchased a new water pump. I figure if I'm going to tear it down that far, I might as well change the water pump as well. I'd hate to rent the Fan Clutch tool, do all the work to replace the fan clutch and then have the water pump go out a couple months later.

Any advice on further diagnosis needed would be very helpful.

Any advice on the actually R&R of the Fan Clutch and Water Pump would be very helpful. Last water pump I changed was on a 69 Chevy C10 pickup and took about 15 minutes...lol Only other water pumps I've ever changes were on a 77 AMC Hornet and a 69 Jeep Commando.

 

All of the sockets you'll need for this one are metric. A long extension will be really handy.

Take the upper fan shroud off, should be 7 10mm bolts.
Some like to break the fan loose now before the serpentine belt is off but you can do it later.
To take the serpentine belt off, you'll need a serpentine belt tool. On these trucks a ratchet works well too.... I like to use a 1/2 drive ratchet with a 3/8 adapter for the extra leverage. I actually prefer the ratchet method because I can determine what attitude the handle is in.
At this point it's just a matter of draining fluids, pulling hoses and taking the four bolts that secure the water pump out.
Getting to the left hand mating surface to clean it up can be a little tricky, one of the gasket scrapers that has an angled end makes life a little easier.
While you're in there, I'd suggest changing the thermostat too, if you haven't already. It's in the top of the intake manifold right under the upper radiator hose. It's easiest to get to if you pull the air intake goodies out of the way first.
Hopefully it is just the fan clutch and or thermostat and your radiator isn't all gunked up or anything more involved or expensive.

 

I hadn't thought about it but, you're right. I think I should replace the thermostat while I already have it all apart. Guess one more trip to Autozone won't hurt, they're close and I forgot to buy RTV sealant anyway...lol

 

Probably be best to break the fan loose before removing the belt. I did it the hard way when I replaced my water pump. I couldn't get the fan loose and ended up pulling the radiator and then puling the water pump and fan as a unit. What a pain in my... Trans fluid, coolant, oil (from the oil cooler) dripping all over my driveway out of the radiator.

Back to your fan clutch question. If it overheats at idle and slow driving, it is an airflow (fan) problem. At highway speeds, the fan does basically nothing; the 60+ mph headwind is sufficient to cool the engine.

While you got it all apart, why not flush the coolant, also? There's a how-to on this site. Dex-cool tends to deteriorate over time, and if anyone has mixed "green" with it, you are bound to have problems. Don't forget to flush the heater core both ways when and if you flush the rest of the system.

 

Cleburne just reminded me of a time when couldn't get the fan nut to break loose while the water pump etc was in the truck.
It is possible to remove the water pump with the fan attached without removing the radiator.
To do this, you need to remove the alternator, it's mounting bracket, tensioner and idler pulleys.
That can all be accomplished by removing the 3 big bolts and a nut from the front of the alternator mounting bracket, the heater hose bracket and wires from the alternator.
There is enough room to slide the whole assembly off of a stud. Then the water pump and fan can be maneuvered out. It's a little hassle but a whole lot better than messing with transmission cooler lines etc.

 

I wished I had tried that. Pulling the radiator is super messy, and I swear, the ATF cooler lines shrunk while they were disconnected. Seemed like they were a good inch too short when it was time to reattach them. I must have argued with those darn things for an hour!

 

The trans cooler lines have always been a little fight for me too. They're one of those things that drip on your nose when you finally get into a position where you can get them threaded on right etc. Then you're extremely lucky if one of them doesn't leak a little initially upon reassembly.
I thought up the idea to pull the alternator while I was smoking a cigarette and dreading pulling the radiator in a Jimmy. I really don't know if it's something that others have done but know that it works on 2nd gen stuff.
Glad you won the fight, I've been there and know it's not pretty.