Up front please excuse me if I'm not a savy and some of you are. But I need some help and hopefully someone can give me an answer. This is my first diesel. I bought it new in 2005. The paper work says it's a Duramax Diesel 6.6L Turbo V8 Engine. I need to change the coolant in the truck.
I have changed the coolant in all of the cars with gasoline engines I've owned over the years. I have always used the Prestone Tee installed in the heater inlet hose. Drained the coolant and running a water hose to the tee ran the engine for a while to get all the old antifreeze out and then drain the system again. With it drained I fill the system half full with staight antifreeze and then add water to top it off...But I need some direction as how I should go about it on the truck.
If this tee method is acceptable for the Duramax how can I identify which is the heater inlet hose? I read somewhere that the engine has two drain plugs on the bottom of the engine?
I need some direction on what steps to take and identifying the plugs etc. Any photos would be of great help. And a step by step procedure.
I do appreciate any help. I try and maintain my stuff myself........can't afford to pay anyone when I can do it myself. So I so appreciate any help, suggestions etc anyone could share. And thank you in advance for helping me.
God Bless
GMCPapa

There is a radiator drain on the lowest passenger side corner of the radiator. It is a plastic fitting and should unscrew somewhat easy.

If it was me I would drain from that point, fill and flush with water, then fill with new dexcool in the mixture that you need for your area. I don't see the need to do a T in a heater line with the rad. drain.

Just my .02

^^^ what he said. I flushed mine a few weeks ago, easy job only took a few mins.

I used the Prestone T to flush using the garden hose. I T'd at the heater hose connection that is easiest to get to, near the fuel filter.

I didn't leave the T installed, or cut any of the heater hoses. Instead, I used a short piece of temporary hose between the T and the metal connector that the heater hose connects to.

When done flushing, I removed the T and drained the water as much as possible. I then filled with distilled water, ran it, drained it. I might have done this again, but it was a year ago, so I forget. Then I filled with full-strength Prestone Dexcool. The water left in the block will result in a dilution of about 50-60%. By knowing the cooling system capacity, you can also compute how much Dexcool you need (2 gallons, I think, but mine takes a little more with the aux V2 radiator).

Use the bleeder on the front thermostat housing when filling, until water comes out when filling with distilled water. Use the bleeder until antifreeze comes out when filling with antifreeze.

Dexcool may have problems with non-distilled water, and with air in the system. That's why you should do the final flush with distilled water, and that's why you should use the bleeder.

You should also rinse out the plastic reservoir. BTW you fill the radiator through the plastic reservoir.

Depending on where you live, I would try to avoid using tap water. When I do mine, I pick up a couple of gallons of distilled water from the store. Where I live there is so much iron and calcium in the water that it could cause hot spots in the block.

I do keep my eye on the overflow bottle. I usually just drain the radiator, refill with 1 gallon pure dexcool, then top off with distilled water, watching the bleeder screw until fluid comes out. I also go through the trouble of taking both hands and squeezing the upper radiator hose to get as much air out as possible.

I found the drain at the PS bottom of the radiator but the only way to use it is to remove it completely. When it came out it fell into the bucket and the coolant came out all over. I captured MOST of it, however a little bit spilled out. Too bad you can't direct it better.

Questions:

I only got about 2 gallons out of the radiator. I did remove the cap on the overflow tank. I thought I would get more than that. My guess is that I should refill it and try to get some more out before filling with Dexcool. Does this sound right?

I have read several posts that state you should remove the bleeder screw to know when it's full. WHERE is that screw?

If I use the above procedures to fill the system is there a possibility of air in the system? Will it bleed out itself? If not, how do you remove it?

The bleeder screw is just to the left of the air conditioner compressor on the top front center of the thermostat housing. Almost looks like it should hold down the thermostat housing.

When you remove the screw, you may get more out of the system. You could also try turning the truck over for a couple of seconds to see if any more coolant comes out ( I have not tried this yet ). Like I stated earlier, I just remove the rad drain, and refill. As long as the fluid is not changing color from rust, there should be no contamination in the system to warrant a chemical flush.

A lot of the coolant will stay in the lower part of the block-- so the only way to get all coolant out, is to remove the drain plugs at each side of the block. :D

Moved to Maintenance and Fluids

I have a water softener to remove minerials since the water is very hard. But, water softeners leave a little salt in the water. Does this matter?

How do you get rid of the old anti-freeze? Update: Just googled this and found out antifreeze has to be taken to hazardous waste dropoff. No charge for dropping it off.

If it were mine, I'd avoid home water period, and go by distilled water.
Drain radiator and reservoir, fill with distilled water, run it enough to open thermostat and mix, then drain again, refill, run it, and drain again.

As said above, fill through expansion tank, radiator drain on lower passenger side, (accessable through wheel well), vent bolt on thermostat front top of cover.
Two block drains on lower side of block, accessable through wheel wells, painted yellow.

The filling/vent procedure is to fill through expansion tank, and vent through T-Stat vent bolt. Loosen expansion tank cap so system doesn't build pressure, then run truck and heat up to open T-Stat. Watch level, fill as needed to the plastic tab above mid-seam of tank.
For the next few heat-up/cooldown cycles, watch tank level and fill as needed. You know all air is out of system when expansion tank level rises approximately 3/8 to 1/2" after heatup, the upper radiator hose is firm after heatup, and tank level stabilizes to the same level when checking cold.

If it were mine, I'd avoid home water period, and go by distilled water.
Drain radiator and reservoir, fill with distilled water, run it enough to open thermostat and mix, then drain again, refill, run it, and drain again.

As said above, fill through expansion tank, radiator drain on lower passenger side, (accessable through wheel well), vent bolt on thermostat front top of cover.
Two block drains on lower side of block, accessable through wheel wells, painted yellow.

The filling/vent procedure is to fill through expansion tank, and vent through T-Stat vent bolt. Loosen expansion tank cap so system doesn't build pressure, then run truck and heat up to open T-Stat. Watch level, fill as needed to the plastic tab above mid-seam of tank.
For the next few heat-up/cooldown cycles, watch tank level and fill as needed. You know all air is out of system when expansion tank level rises approximately 3/8 to 1/2" after heatup, the upper radiator hose is firm after heatup, and tank level stabilizes to the same level when checking cold.

Modified,

Thank you very much for this. It is very helpful.

One thing I am going to do to "push out" more water is to pour the DexCool into the reservoir with the drain open. I noticed this when I filled with water to cycle it out. When I poured the water in, the "old" fluid came out.

What would be wrong (other than being expensive) with draining coolant, refilling with dexcool, running engine to operating temp and to circulate. Then drain again refill with dexcool? My coolant is not nasty at all at this point.

I'm concerned that if I flush with water and then do the final fill of dexcool that I'll have to much water and not enough anifreeze.

Nothing at all.

The word everyone throws out around here is "preventive maintenance".... but few do it.

Letting your cooant turn rancid..... powerflushing it all out, filling it, draining it , flushing it again, and refilling it is not preventitive maintenance.

I drain my cooling system every 3rd oil change ( bout' every 30,000 miles) buy some DEXcool and some distilled water.... mix it 50/50, and refill it.

Costs about $20. Done.

It always has fresh coolant this way, no worries ....

Same goes for the hydro boost system, Diffs, T/C case....

These trucks need P/M.... not Pseudo- P/M

Does the truck purge the air on it's own? I left the cap on the reservoir very loose and slowly drove around the block a few times until it heated up. I removed the bleeder screw and coolant came out. Does this mean that all the air is out of the system? The reservoir level hasn't gone down now after two days of driving.

I know this is an older post, but I did flush my system today... biggest problem.. temps outside were not as friendly as I would have liked... hovering around high 30's.

What i saw in my manual I thought was 24 quarts to fill, so I drained, flushed, flushed, then filled. It didn't take long, however I ended up putting in 3 gallons of Dex and 1 gallon of water.. which is 16 gallons... am I that off ( 8 gallons) of did it not fully flush out??

I know this is an older post, but I did flush my system today... biggest problem.. temps outside were not as friendly as I would have liked... hovering around high 30's.

What i saw in my manual I thought was 24 quarts to fill, so I drained, flushed, flushed, then filled. It didn't take long, however I ended up putting in 3 gallons of Dex and 1 gallon of water.. which is 16 gallons... am I that off ( 8 gallons) of did it not fully flush out??

Draining just the radiator, you should get a little more than 3 gallons out, which is 12 quarts or about 50% of the the whole cooling system. You won't get all of the coolant out unless you drain your block which most people don't do. Do this every two or three years and your system should be free of stale coolant.

I dont like moving fluid around or adding water to flush as the mix will never be right, I just drain and refill once a year and call it done, cost $30 and flushes half the fluid.

I do the same with powersteering fluid and brake fluid, suck out the old and fill with fresh, doesnt get it all but do it once a year and it will always look great.

I agree. It is hard to get the mix correct after a water flush, since some water remains behind. If I were to do a flush, I would not use anything but distilled water since some of the flush water will remain behind. I just change the coolent in the radiator (about half the total system) every two to three years, which keeps the coolant fresh, and I use a coolant filter.

Let me add a question to the thread. I drained my rad 1 week ago and used the bleed bolt on the t-stat. Note though: I closed the bleed bolt when a mixture of air and coolant came out but closed prior to straight coolant.

My engine temps are currently low and have been since I did the change. do you think I have a air bubble that would cause the low temps?

Cheers all.

Air in the system can only make it run hot not cold. Crack the cap open and drive it if you really think there is air in it.

Air in the system will affect the temperature reading, and the heater operation. Hot air does not transfer heat like hot coolant does.

You might re-bleed the system.

I just replaced my water pump , and the lower hose . so now I filled up with three gallons of dex . ( five came out when I removed the rad hose )

I tried bleeding with the air bleeder on the t-stat, I have dex coming out , the bottle shows filled.

My temp guage wont budge it shows under 160 and I am blowing cold air for heat .. I know I am air bound any suggestions on how to bleed the system ???

I just changing the radiator just a couple weeks ago. Everything came out very clean, it had never been changed. I tow, haul and plow.
I will do another flush some time down the road, but I'm not worried currently about the cooling system at all.

My temp guage wont budge it shows under 160 and I am blowing cold air for heat .. I know I am air bound any suggestions on how to bleed the system ???

See bleeding procedure at post #11.

Is the drain still on pass side of Radiator can't find even took off the fender inter liner 2007.5 GMC????????????

I believe in 06 they quit putting them on there???? You'll probably just have to pull the bottom hose-

I believe in 06 they quit putting them on there???? You'll probably just have to pull the bottom hose-

Mine did not have a drain. Pulled the bottom hose off. If you leave the cap on the resevoir, it won't come gushing out so fast.

You can also cut the heater core return hose where it paralells the lower raditor hose and install a tee with a plug. This controls the drain flow and maker future changes much easier and less messy.

turns out that i was air bound ,, the best way to push it out ... I put pressure on the overflow bottle to push dex into the system ,, that fixed the air lock ..

heres a question whats the temp that everyone is running at..
I was running steady near 200 degrees ,, now after the new water pump and coolant , its runs steady like 160 degrees ,if I drive at a long grade it jumps to the old temp of 200 .. after the hill it comes back down to 160 .. anybody find this in there trucks ?? is this normal? whats the remedy my system seems full .

Mine always runs just below 200, but it is a lot warmer here in So. Cal. Maybe you need to use a winter cover?

thats what i ran before the coolant change ......sorry didnt mention it but everything mentioned so far is with the cover on and still running cooler than before

heres a question whats the temp that everyone is running at..
I was running steady near 200 degrees ,, now after the new water pump and coolant , its runs steady like 160 degrees ,if I drive at a long grade it jumps to the old temp of 200 .. after the hill it comes back down to 160 .. anybody find this in there trucks ?? is this normal? whats the remedy my system seems full .

thats what i ran before the coolant change ......sorry didnt mention it but everything mentioned so far is with the cover on and still running cooler than before

Sounds to me like you still have air in system, causing inaccurate temperature indication, and due to poor heat transfer of air, and the engine may actually be running hotter when underload, (going up-hill).

Fill expansion tank to tab above tank mid-seam, loosen the expansion tank cap, run truck to heat-up and open T-Stats, add coolant if level drops. Crack open T-Stat housing vent bolt to purge air. Turn In-Cab heater to HOT to circulate water through core.

Now, after next several coolsdown cycles, monitor level in expansion tank and refill to plastic tab above tank mid-seam.

You'll know all air is out of system when:
1. Tank level rises approximately 1" after heat-up.
2. Upper radiator hose is very firm, (when squeezed with hand), after up to operating temp.
3. Expansion tank level returns to constant level of plastic tab above tank mid-seam after each cooldown.

thanks modified will do and get back with my findings

Great info - modified thanx.
All the other tips are great too..thanx guys.!

Water pump replacement coming very very soon.

Theo

If you really want to understand the cooling system, read "The Degas Demistified" in link below.
It may seem long, but there is very much great info in it.
Thanks killerbee.
http://killerbeeperformance.com/downloads/miscellaneous/

This info was posted some years back on this Site, in post #1 below:
http://www.dieselplace.com/forum/showthread.php?t=49060&highlight=canoworms

I don't have a radiator drain plug on my 07 so I pull the wire keeper on the lower radiator hose (passenger side) and pull the hose off - carefully to avoid a mess. I get 2 galons out that way - one gal dexcool and one galon distilled water for 50/50 solution. I do this once a year to replenish the coolant instead of taking out a block plug. I re-fill through the overflow and crack the bleeder screw on the thermostat housing. I drive around a bit to crack the thermostats and top-off the overflow. No problems yet.

I just did mine for the first time, a 2005 2500 HD D/A with 35K miles. Drained the coolant via the plastic plug near the passenger side wheel well. Pretty easy to get to if you turn the wheels to the right. Controlled the flow somewhat with the cap on the coolant tank. Captured a vast majority of the coolant with a Rubbermaid container, although still a little messy. Then loosened up the clamp on the return (upper) hose and it drained some more. Replaced the plug and then added about 2 gallons of Dex Cool and distilled water mix. Started the engine, cracked the thermostat vent and then drove around a few miles to get the engine up to temperature. Closed the vent, squeezed the return hose a bit and added about 1.5 gallons more mix to top it off. Plan to keep an eye on the tank and add additional coolant as necessary. Hopefully all went as well as it seems. Cost about $32 total. Thanks to everyone who posted info; great site. Transmission, transfer case, and diffs next.

I just did mine for the first time, a 2005 2500 HD D/A with 35K miles. Drained the coolant via the plastic plug near the passenger side wheel well. Pretty easy to get to if you turn the wheels to the right. Controlled the flow somewhat with the cap on the coolant tank. Captured a vast majority of the coolant with a Rubbermaid container, although still a little messy. Then loosened up the clamp on the return (upper) hose and it drained some more. Replaced the plug and then added about 2 gallons of Dex Cool and distilled water mix. Started the engine, cracked the thermostat vent and then drove around a few miles to get the engine up to temperature. Closed the vent, squeezed the return hose a bit and added about 1.5 gallons more mix to top it off. Plan to keep an eye on the tank and add additional coolant as necessary. Hopefully all went as well as it seems. Cost about $32 total. Thanks to everyone who posted info; great site. Transmission, transfer case, and diffs next.

Don't forget the Hydroboost!! (See the DIY section)

So if i drain the rad and the block, how much will come out? If i do this, csn i just add however much dexcool came out? I.e.) drain 4 gallons and then refill with 4 gallns? All the flushing with water and draining and whatnot just seems excessive, plus i dont want to have the wrong mixture. Im thinking just drain evrything and add new dexcool

So if i drain the rad and the block, how much will come out? If i do this, csn i just add however much dexcool came out? I.e.) drain 4 gallons and then refill with 4 gallns? All the flushing with water and draining and whatnot just seems excessive, plus i dont want to have the wrong mixture. Im thinking just drain evrything and add new dexcool

You can certainly do that. Most of us just drain the rad on a regular schedule which exchanges about 50% of the coolant each time. You can also buy Dexcool 50/50 which is premixed at Wally World for 8.50 gal. Maybe a little more expensive, but worth it to me. If you mix yourself, be sure to use distilled water (available at the grocery store).

If your coolant hasn't been changed, then you might be better off draining all of it, though it involves a little more work. I'm told there are two drain plugs on the D-Max block.

Very important: Which ever method you use, refill and then monitor the levels in the recovery tank for the first few trips. You can also bleed most of the air in the system by loosening the bleed screw on the thermostat housing. DO NOT LOOSEN THE RADIATOR CAP WHEN HOT.

Thanks, another question. Im about to replace the injectors in my truck so the coolant will need to be drained anyhow. I have a dealer about 3 miles from me. After i replace my injectors, would it be out of the question to just refill with water, assuming there will still be coolant in the block, and drive to the dealer and have them do a full flush and refill?

Its funny, i dont mind tackling injectors or a pump rub kit, but this coolant flush stuff seems like it will get on my nerves.

Thanks, another question. Im about to replace the injectors in my truck so the coolant will need to be drained anyhow. I have a dealer about 3 miles from me. After i replace my injectors, would it be out of the question to just refill with water, assuming there will still be coolant in the block, and drive to the dealer and have them do a full flush and refill?

Its funny, i dont mind tackling injectors or a pump rub kit, but this coolant flush stuff seems like it will get on my nerves.

Compared to changing injectors, a coolant flush is a "walk in the park".

If you are going to drain your coolant anyhow, why not just refill with Dexcool 50/50 and be done with it. The dealer is going to slam you at least $125 for a job that will take you 15 minutes. I would not recommend re-filling with tap water. Even though you will only travel 3 miles with water only, you will have removed the lubricating ability of the anti-freeze (coolant) which is not good for the water pump. Why introduce the lack of coolant into the system when all you have to do is pour in some Dexcool? With 158,000 miles on your truck, if it hasn't had a water pump replaced, you could be inducing a water pump failure by running with no antifreeze. Why take the chance?