anti freeze question..,,,

[spongebob]

I dropped the bottom radiator hose, let it drain, blew wind in the tank, removed the bolt in the thermostat housing..then
replaced bottom hose and the system only took a little over 3 gallons before it came out the thermostat hole...

[spongebob]

I drove the truck around a bit got the temp up over 185* on the gauge it took more but just under 4 qts...
tested the freeze point..0*

[JohnC]

tested the freeze point..0*

That doesn't sound good...

[DmaxMaverick]

Yeah, only zero doesn't sound good, maybe. The least concentration recommended is 33%, which rates it about -4F, close to what you have. It must have quite a bit more water in it than it should. Did you flush it with water? Use 50/50 mix, or mix it yourself? That's curious, if you didn't flush, and used only 50/50. I'd question the accuracy of your hydrometer. 50/50 Dexcool should be right at -40.

The proper air purge procedure for early (through LBZ, not sure about later) Duramax engines is, fill it, bleed like you did, fill the reservoir just short of full, cap off or loose, then do several (like 4-6, I like 6) 30 second runs at 3000 RPM's, after it's up to operating temp (140F+). I ease off the throttle slowly to prevent any fluid push-back that can leak out. More air in the system can allow for more push-back. Let it idle and check the reservoir after each cycle. That should purge any significant remaining air.

[spongebob]

I changed out the rubber heater hoses, refilled it with water, to check for leaks. no leaks so I pulled the bottom hose, removed the vent bolt.
I didnt flush it with clean water because most all the anti-freeze was removed earlier..I was have intermittent leaks so I ran water only.
I used a 50/50 mix to refill, I drove the roads around my home in 2nd gear and wated the temp go to 185* then just short of the 210* mark, it took the mix, I did this twice. I have 2 gallons to go...I dont understand why all the fluid didnt escape when I opened the bottom hose and vents..

[DmaxMaverick]

The engine and remainder of the system will retain a lot of coolant. The bottom of the block will also retain a lot of coolant. It has drain plugs lower than the frost plugs for a complete draining. The lower hose will drain the radiator, but the other end is about mid-engine. That's much of the reason for the purge procedure. Those areas that retain coolant can also trap air, or prevent it from moving out easily. Your use of water explains the lesser concentration. Not a big deal if it never sees temps near zero F. The difference between just freezing and near zero is quite a lot. It freezes here every year, but I've only seen single digit temps in this area once, in 1991. Low to mid teens are very rare, like only a few days every 20-30 years, but near 20 is common most winters. Most coolant recommendations, regardless of type, color, or application, is a mix of 50%. Dexcool lists a specification at 33%, so it must be acceptable where no more freeze protection is needed. A concern might be corrosion protection, but their spec at that concentration has no mention of corrosion or other additive concerns.

[spongebob]

so the low point isnt the bottom radiator hose then....thanks GM....every video/ thread Ive seen guys just let it rip out of the bottom hose...
Ive changed my coolant many times, never had this problem...I checked it this am, and the reservoir was low so I've added so far, 4 gallons..
now Im sweating spending $100 for new ACDelco thermostats.. I think the ones I have are now napa....

[DmaxMaverick]

Are you having heat issues? Have you completed the purge procedure? What's the reason to replace NAPA stats?

A normal drain/fill service doesn't include adding water for a while in between. A flush and fill service calls for a block drain, as I recall. The first, would keep the 50/50 mixture strength, mixing some old coolant with new. This is OK, if you follow the GM recommendation of servicing at 5 years or 150K miles. I run mine longer (low mileage), but I do a complete replacement with 50/50 concentrate and distilled water. I know there are a lot of Dexcool haters out there, but if used correctly, it's better than the distant second place winner that requires replacement like skivvies.

[spongebob]

the only temp issue Im having is my temp gauge now fluctuates, when the truck was new it ran one mark under the 210* line, now it fluctuates between 185 and 205*.
my deal now after changing the rubber heater lines, I drained the system, like always dumping the bottom radiator hose and refilling with 6 gallons of fluid...but now it took only 4..I have a friend that has a 04 duramax, he gave me a link saying the 06 takes 20 quarts owners manual says 25.6 quarts...and he said his 04 took 20 quarts..I dont remember (Im old now) why I put in new t-stats..
Im now hearing of the plugs on the block that Ive never taken out....If only I could get my hands on the engineering of this truck.... so what Ill do is drain some fluid, and add straight antifreeze to get to a good freeze number. thanks for your input...

[DmaxMaverick]

Your temperature range is within normal, although it may seem less smooth than with the previous OEM stats. If it's no more than that, and you don't have other issues, such as erratic fan engagement or the range swinging outside an extreme, I think it's just a matter or your preference, but it isn't hurting anything.

GM's, as with any mfg's service procedures, list several conditions of capacities and service capacities. Total system capacities and service capacities almost always vary, often greatly. Engine oil capacities often include with and without filter volume, total capacity vs. drain/fill capacity, transmission total fluid volume vs. service capacity, etc. None of this is unusual, and falls in line with your service manual info vs. your friend's claim of coolant capacity of his truck, and my experience has also been the same. I'm not aware of a (significant, or notable) difference in coolant capacity between the LBZ and earlier model years. Someone should correct me if that isn't accurate. I don't consider differences of a quart, a few quarts, or even a gallon or two to be a significant difference in large capacity systems, such as coolant or transmission. They can vary that much between identical models, with no explanation. I prefer to do complete and thorough fluid services, but most folks don't, and vehicles aren't burning up across the country, for that reason, anyway. We can split hairs and pick nits, but to what end? I wouldn't sweat it.