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LML Coolant Drain and Refill

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115K views 46 replies 23 participants last post by  rcwbailey  
#1 · (Edited)
My LML only has 45k miles, but its 5 years old, and time to service the cooling system.

As many of you know, GM in its infinite wisdom did away with any convenient way to drain the cooling system by deleting the radiator petcock.

I looked into not so convenient ways like block drain plugs, to no avail. Even removing the lower radiator hose looks like both a pain in the rear, and a guaranteed mess maker, with coolant spraying everywhere.

NOTE: Some may flame me for what I am about to describe doing. Thats ok. I did it as a lessor of two evils. I'm not a big fan of altering OEM stuff, but sometimes you have no choice.

First thing to do is jack up your truck, and get some room to work with. Then pop off the front plastic skid plate to get access to the lower radiator hose area. Next, pop off the clamp that secures the smaller hose ,to the larger one.

I went into the kitchen and grabbed these big scissors we have, that cut just about anything... and in a quick...SNIP, I cut the small lower hose in two.

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Obviously, you want to do this with the truck cold. You plug one side with your thumb, while the other side drains into the bucket. I only lost a tiny bit of coolant when I did the Snip. It was quick and easy.

This hose is at the very lowest point in the cooling system,which is another reason for doing it this way, and will drain the entire system. Its about 3.5 gallons.

Next, you want to splice it back together. You will need a 5/8" splice, and two 1" spring clamps.

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The splice fits a little loose, so the hose must be metric. If anyone makes a 17mm hose splice, this would fit perfect.

Splice it back together, and reinstall the OEM mounting clamp.

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There is no "bleed plug" anymore either, so to refill the cooling system you need to fill it all the way up, start the truck, wait for it to get warm so the thermostats open, then fill it again.

And thats about it. Like I said, this method may not be for everyone, and thats understandable, but its one way to deal with the issue.

:gearjamin
 
#19 ·
I like the idea of a coolant drain in the lower radiator hose, the lowest part of the cooling system. I measured my lower hose and it seems bigger than 1 3/4" in diameter one you listed. I did some searching and found one specifically sized to the Duramax application. I have ordered and received it. I haven't had a chance to install it yet. I'll report back later when i do. Here's a link to the one I found:
MFR EcoDrain For Duramax Engines | Diesel Engine Coolant Systems Maintenance Products
 
#46 ·
I like the idea of a coolant drain in the lower radiator hose, the lowest part of the cooling system. I measured my lower hose and it seems bigger than 1 3/4" in diameter one you listed. I did some searching and found one specifically sized to the Duramax application. I have ordered and received it. I haven't had a chance to install it yet. I'll report back later when i do. Here's a link to the one I found:
MFR EcoDrain For Duramax Engines | Diesel Engine Coolant Systems Maintenance Products
I did the same thing after reading your solution.
I used a 400 degree stainless hose splice.
Here are the parts.
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#9 ·
I have 80,000km on my '13 lml. Is changing the coolant something I should do?
 
#12 ·
do yourself a favor and switch it over to the green coolant if you have a way to get all the old out because you don't want to mix the two. the dex-cool seems to be harder on things. I recommend 3 years or 50-60k. if you think about it its cheap insurance and easy maint. once your cooling system goes to crap it is nearly impossible to get it clean again without replacing parts. just my .02 but im a technician and I see the bad a lot
 
#15 ·
By that do you mean stick with the Dex cool or not? I've found you to be a reliable source on here but this answer left me a little confused. I'm getting ready to change mine.
 
#14 ·
yea I guess the newer dex-cool is prolly better than the older stuff but ive seen dex-cool horror stories so I tend to not like it. wen they first came out with it it was supposed to be serviced every 100k or 5 years and before those intervals ive seen it turn to crap and almost un-fixable cooling systems without replacing parts. to each is there own I guess and everyone has a different opinion.
 
#16 ·
First, colour should not be a basis for coolant selection, since different sources may supply the same 'type' of coolant in different colours.

Yes, stick with Dex-cool in your Duramax, but don't just select a brand based only on colour - be sure it is an OAT coolant.

Often, products are available in both concentrated and pre-mixed versions. FWIW, I'm a fan of using pre-mixed coolant so I don't have to be concerned about my water source messing with the coolant pH and the additive package. (and I'm too lazy to source purified/distilled/de-ionized water)



(AND If you have an older engine that was not designed for dex-cool, DO NOT put dexcool in it.)
 
#18 ·
I ran green junk in the LLY after it was built, but I didn't have long enough to see the aftermath but have seen others run fresh builds with it with no issues
. I run the orange extended life delo shit we have at the rig, dex cool is the best option for most but other stuff will work with a good flush or a fresh build.
 
#21 ·
Just did this today at 43,000 miles and 2 years on my 2015. Started by pulling the lower radiator hose through passenger wheel well which got about 2.5 gal out. Then decided to bite the bullet and crawl under to snip the heater hose. Got another 1/2 gallon or so come out. Proud to say not a single drop on the driveway or my t-shirt :D.

Anyone forsee corrosion issues using a 5/8? brass hose barb coupler to patch the cut?
 
#28 ·
Hey dieselfelon, you get a chance to install that drain adapter? Looks like a decent and easy to use product. Thinking about getting one and put a petcock drain valve on it instead of the bolt and washer(?) that appears to be with it on their webpage. Thanks.
 
#31 ·
Dieselfelon, have you installed that drain adapter yet? It looks to be a good idea.
I finally found some down time over the holidays and got it done. It was a painless non-event.
To drain the coolant in preparation of installation, I poked the lower hose with a knife and them jammed a piece of air brake line in the slice. I used the air brake line to direct the draining coolant stream into a pail. By doing that, I didn't have to pull a lower radiator hose end off and dump that crap all over the floor or into a Walmart kiddy pool that I will have no other use for. I poked the hole in the lower hose at the location at which the new drain would be installed. Once the coolant had completely drained, I cut the hose completely, trimmed the ends square and installed the drain. I used heavy duty "T" bolt style clamps like used on hydraulic return or suction hose. I ordered a few different size clamps to be sure I would have the right size on hand to complete the installation. The clamp that fit best was stamped 2.2"-2.32". The drain plug is 1/2"-20 thread. In fact, the supplied drain plug looks to be an engine oil drain plug for GM engines used for over 40 years and available at any Napa. It's nice to know that if I need to drain my coolant, it will be quick, clean and hassle free. I hate cleaning up anti-freeze mess from the shop floor.
Here is a link to the company making it:
MFR EcoDrain For Duramax Engines | Diesel Engine Coolant Systems Maintenance Products
 
#30 ·
Dieselfelon, have you installed that drain adapter yet? It looks to be a good idea.