2002 Astro cooling system advice.

I recently experienced DTC P0128 (Coolant Temp Below Thermostat Regulating Temperature). After googling for this problem I first checked to see if the coolant was low. It was a little. It took less than half a gallon to fill. The temperature seems find now, but I have only driven it around 30 minutes after topping off the coolant.

What concerns me is that with the coolant a little low I noticed a sludge coating the inside of the radiator. Something I missed when I purchased the vehicle (used) about a year ago. It appears the previous owner must have fixed a coolant leak with a stop leak product.

Having no experince with these products I was hoping someone here could tell about flushing my cooling system. I am afraid if I do so now, that I will flush the stop leak away and re-introduce the leak. Since it is winter. I don't want to fix the leak properly until next spring.

Also, can this stop leak product even be cleaned out of the engine allowing me to find the original leak so I can fix it?

Thanks!

I have been speaking with friends and googling all morning about my problem here and have just learned about Dex-Cool and it's slidge problem. I do not know yet if my vehicle used Dex-Cool. My wife has the astro now and the owner's manual is in the vehivle. So this is may be the sludge I see in my cooling system.

I also wanted to say that the Service engine soon light turned itself off after topping off the cooling system. Also I was able to put the rest of the jug of anit-freeze/coolant in the vehicle and in the overflow container after driving to work this morning.

I am still very concerned about this sludge I see, especially after reading about the class-action lawsuit against GM for Dex-Cool.

Can anyone offer insight from their experience with Dex-Cool sludge problems?

Thanks again,
Donny Baugh

Donny,

Your vehicle requires the use of Dexcool coolant. GM recommends flushing at 5 years or 100,000 miles which ever occurs first. In reality, flushing at 30,000 miles or 2 years eliminates the sludge problem. Do not, under any circumstances, use anything other than genuine Dexcool coolant or mix any other type of coolant with it, or you will encounter sludge, guaranteed! The heater core and radiator are typically the first things to be affected by the sludge, and are also the most expensive to replace. This link explains: http://free-auto-repair-advice.blogspot.com/search/label/Dex-Cool

If your sludge problem goes untreated, the entire cooling system, (radiator, radiator cap, overflow reservoir, heater core, thermostat, coolant passages in the engine, hoses, intake manifold gaskets, water valve, etc, etc), will become contaminated. I service an entire fleet of 4.3's and I have found that flushing at 30,000 miles virtually eliminates problems with the cooling system, (some of the fleet vehicles have over 300,000 miles and have never had a cooling system problem).

If your system has a leak, which it sounds like it does, leaking intake manifold gaskets are a known problem on 4.3L engines. Cooling system neglect is partially responsible. A cooling system pressure test will tell where the leak is coming from. Hope this helps.