Question on Express 3500 Cooling System

[HiccaBurp]

My '03 Chevy Express 3500 6.0L has 110k miles with original cooling system. Somewhere in it's life, green coolant was added. Not sure if it was compatible or not. Employees who didn't know better just added probably what was cheapest.

This past weekend I decided to drain and flush all the coolant. I removed the thermostat to give a nice flow of water to clean everything out. Couple of things I noticed..

1. With the thermostat out, the water just didn't seem to flow with much volume/pressure? How can you test if your water pump is starting to fail? It has movement, just not as hard as other cars.

2. After filling up with water and Peak cooling system cleaner, the system didn't "burp" much. I have one of those cooling system funnels that attach to your radiator and you fill and let the system burp itself. I would think there would be more air/water exchange going on.

3. I left the thermostat out to run the water/cleaner thru for a few hours and the water in the overflow tank stayed about the same. Maybe the fact that the thermostat was out filled the system more completely without many air bubbles?

Radiator fan clutch.. how can you test it?

1. When the engine is off, you can spin the fan freely.

2. When you turn it on.. the blades start to spin slowly.

3. When it gets hotter, it doesn't seem to spin much faster? I know with my other vehicle which has electric fans.. you can hear when the fans kick on.

4. Is there a way to test the fan clutch?

Thank you all for your help!!

 

[SteveSRT8]

We own a few of these in the GMC version.

Please use Dexcool as it is the best product for these engines.

The radiator is reverse flow, so you won't see much movement. We typically get over 200k miles out of a water pump so yours is probably fine.

There is a "must do" procedure for refilling these, did you pull the upper hose and fill it through there? If not you can damage a head gasket or worse. Very important!

The fan clutch is more than likely bad, the fan should never spin freely even if it is a thermostatic one.

 

[HiccaBurp]

Originally Posted By: SteveSRT8
We own a few of these in the GMC version.

Please use Dexcool as it is the best product for these engines.

The radiator is reverse flow, so you won't see much movement. We typically get over 200k miles out of a water pump so yours is probably fine.

There is a "must do" procedure for refilling these, did you pull the upper hose and fill it through there? If not you can damage a head gasket or worse. Very important!

The fan clutch is more than likely bad, the fan should never spin freely even if it is a thermostatic one.


Thanks for the quick reply! Yes, I intend to use DexCool. Do I have to purchase at GM dealer, or do stores carry genuine DexCool?

As for filling, yes I filled thru the upper hose. Actually, the garden hose was in the radiator and the water was coming out of the upper radiator hose. This seemed like the direction of flow? When I put the garden hose in the upper rad hose, it didn't seem to want to fill so I figured it was against the pump flow??

I plan on leaving the water and cleaner in for another day or two and then drain everything and fill.

As for fan clutch, what your saying is I shouldn't be able to spin by hand? Not what my neighbor who races cars said. He said at engine cold and off you should be able to spin by hand? Can someone else please confirm? It's not a cheap part, but if it's broke.. I do want to replace it.

 

[440Magnum]

Originally Posted By: HiccaBurp

As for fan clutch, what your saying is I shouldn't be able to spin by hand? Not what my neighbor who races cars said. He said at engine cold and off you should be able to spin by hand? Can someone else please confirm? It's not a cheap part, but if it's broke.. I do want to replace it.


Its a subtle thing, and its hard to describe to someone over the internet. If the fan clutch really is COLD, then you should be able to rotate it by hand and feel a light resistance. If its hot, the resistance should be stiffer but you should still be able to turn it. You should NOT be able to spin it so that it continues turning after you let go when its hot. As the engine heats up, you should be able to hear more fan noise as the clutch tightens. When you shut the engine down HOT, watch the fan. If it keeps spinning more than a few blades (anything more than 1 turn of the fan) then the clutch is probably bad. If it spins 4 or 5 turns and lazily comes to a stop, its DEFINITELY bad.

 

[JHZR2]

Wasnt there a newspaper trick to stopping the fan to test the clutch??? like a rolled up newspaper stopping it somehow?

 

[JimPghPA]

Fan clutchs have friction material like break pads. And just like a break pad they wear out. At 110 K miles it is worn out.

For some vehicles like my 1985 Olds Delta 88 you can get an extra heavy duty clutch that will kick in better, but you will have much more fan noise.

When I uses my Olds a lot, I figured that most wear on friction surfaces of fan clutch was in cold weather where it drags some but is not completly engaged. I use to keep old fan clutch and put it on in the fall, and then change back to newer heavy duty in the spring. I used seeing, and not seeing people with cut-off pants in publid as a guide as to when to change from one to the other.

 

[440Magnum]

Originally Posted By: JimPghPA
Fan clutchs have friction material like break pads. And just like a break pad they wear out. At 110 K miles it is worn out.


To the best of my knowledge, they use a heavy viscous fluid and shear it between the housing and a plate or bar attached to the input shaft. There's no sliding friction at all. When they fail, its either because the thermal spring no longer re-directs the fluid correctly, or the fluid has started to leak away.

 

[SteveSRT8]

^^Right. There is no hard friction material in a fan clutch, only silicone fluid. Some are thermal and some are rpm actuated.

AC performance is an easy indicator. Also I like 440's watch it when someone shuts off the vehicle. It should stop quickly.

It is easy to MOVE, but it should not spin easily, just a nice viscous drag.

 

[bullwinkle]

If you do stop and go driving, running the A/C wide open, in this 95-100F heat, and it's NOT on-it's bad!

 

[mechanicx]

You can use any brand of Dexcool that is Dexcool even the Prestone from Walmart. The dealer may be selling ACDelco Dexcool that is no more than rebranded Prestone. If you want the original Dexcool and the one I think is best get Chevron Havoline Dexcool. That can be hard to find. Zerex is also good. But like I said even Prestone Dexcool would be fine and is the most available.