Chevy 2500 HD 6.0 question

jkilroy wrote:

What’s the cooling stack?

And anyone know if you have to change the water pump with the clutch fan?

No, cooling fan is separate from the water pump. As mentioned, the stack is your radiator, A/C condenser, and tranny cooler.....everything that is sandwiched together that cools fluids.

Take a garden hose and spray through the stack with the engine not running. You will quite likely see bug carcasses, dirt, cotton wood fluff, and all kinds of other junk come through. All of these things blocking the passages between the cooling fins reduces cooling efficiency.

Just watching the fan spin doesn't tell you if the fan clutch is good or bad. It's a fluid coupling clutch so even if it's bad the blades will spin a little. When the clutch is working properly it fully engages and makes the blades spin 1:1 with the pulley. When this happens you'll know it because it is a VERY LOUD ROAR. When your truck hit 220*F the other day you should have heard that fan roaring like a firetruck siren. If you did not, that's a pretty good sign your fan clutch is failed and needs replaced. When I towed in the Appalachian's with my '04 Chevy 2500 6.0L we climbed a few good grades around Daniel Boone Nat'l Forest. My engine temps would climb to about 210*F and the fan clutch would kick in. When that happened my passengers started looking around to see if we had an ambulance coming up behind us. :E

Also, as I said before, if you have never flushed the cooling system it's extremely important that you do so. DexCool coolant works just fine, but it has a limited life. You're supposed to flush and change it every 5 years or 100,000 miles. Over time the organic acids in the coolant become oxidized and form sludge. Draining and flushing the system removes the degraded organic acids and prevents the sludge. These extended life coolants work fine, but they need to be serviced at the proper intervals.

One other possibility is your water pump is bad. It might not be leaking, but if you've had cavitation it can cause pitting on the impeller blades which reduces the efficiency. This leads to worsening cavitation and air bubbles which then reduces heat transfer in the engine.

KJ