Cooling system maintenance - GM vehicles

Messages
102
Location
Ontario, Canada
I drained and re-filled 75% of the coolant capacity (Dexcool) from each of our vehicles (99 Silverado - 186,000 km, 97 Lumina - 70,000 km) in March '05 and again in October '05. I did this instead of a flush and fill type maintenence, as we have never had any coolant related problems, got the idea from this forum. Coolant was unbelieveably clean. Question I have is: since I drained this amount (75%) twice in 2005, is it OK for a while? The pH, freeze & boiling point all check out to be OK, checked last week.
 
Messages
23,750
Location
CA
DexCool lasts "virtually forever" due to the lack of sacrificial components in the coolant. The advertised five-year/150k service interval is done so other parts of the cooling system are also inspected and pressure tested. If you drain and refill periodically, such as once every five-years or so, you should be fine. Of course, I'm just going to wait for the DexCool haters to come in and jump all over me.
 
Messages
4,872
Location
MN
DEXCOOL may last forever, but it apparently eats plastic gaskets if not changed out BEFORE 5 years. It's a good thing you changed it. Drop a couple of GM's sealant tabs in there just in case.
 
Messages
132
Location
Idaho
I just changed out a set of those from a '96 3.1 V6. I don't see how they could keep ANY coolant sealed. Installed the FelPro problem solver set and refilled it with DexCool and distilled water. System was very clean.
 
Messages
664
Location
Mobile
Dex Cool and clones "may" offer the best protection of any other coolants, and I haven't been convinced that they cause seal leaks but admit I haven't researched the seal leak issue much. The problem with Dex is the gelling, most of us assume it is because of air in the system but maybe it could be becasue of the age of coolant or some other issue with different water quality or something. I honestly think if you run RMI25 in there you wont have any gelling issues, but I'm waiting for the RMI25 hater who's never tried the product to say different, lol. I would say if you don't have air in the system you should be fine with your method.
 
Messages
1,674
Location
Morrow, Georgia
Ray H, the gel that the RMI25 causes, is apparently all of the crud that is cleaned off the walls. I believe that is what Labman was referring to. I haven't used the product yet so I have no first-hand experience with the gelling.
 
Messages
106
Location
noneyabeezwax
Actually looking at those gaskets you posted the pics of and the comparison to my 97 5.7 IMO it is due to overtorquing.Even though I used a torque wrench and I'm sure you did as well the same failures are commom. I think thats why GM and Fel-Pro when with the steel insert in the bolt holes to prevent that. My previous set didn't have that feature. My new ones do and I will see how long they last. seal tabs
 
Messages
4,009
Location
Calgary Canada
I think someone mentioned in another thread that the dexcool snot is caused by rust forming at the high points of the engine (like water jackets near the top of cast iron cylinder heads). This happens when air pockets develop in those locations from an inproperly purged (or low on coolant) cooling system. I had three questions arising from this: 1. How do you properly purge a GM v8 engine (the 5.3L variety) to ensure there's no air pockets after a coolant change. I don't see a traditional screw in the thermostat body, and that is relatively low on the engine; 2. My GM 5.3L v8 has aluminum cylinder heads. Am I likely better off because the highest points in the engine are aluminum and not subject to rusting; 3. My truck is 2.5 years old with 48k miles. Am I wasting my time changing out the dexcool now? Will I still have a good margin of safety waiting to ~3.5 years and 53k miles? Thanks in advance for anyone's thoughts!
 
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