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Coolant Flush / Hose Change

This is a discussion on Coolant Flush / Hose Change within the GM Trucks forums, part of the Vehicle Specific category; Our 2007 Suburban has about 73,000 miles on her and it's time to flush the cooling system. I quickly found ...

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    Coolant Flush / Hose Change

    Our 2007 Suburban has about 73,000 miles on her and it's time to flush the cooling system. I quickly found that even though it's a big truck, things just aren't going to be easy on this job. First issue I found -- to my surprise -- was that there is no draincock on the radiator. Checking the manual, it advised that to drain the system you have to pull the lower hose. Obviously, this would result in one damn big mess and I was not going to get drenched in the process. I elected to drill a 1/4" hole in the lower hose and inserted a tube cut from an empty spray bottle into the hole. This allowed for a controlled drain of the system and no mess at all.

    Next issue was the NAPA thermostat I ordered. It was loose in the housing and it was no where near as well constructed as the stock thermostat. I ended up returning it to NAPA and dropped just over $50 on one from the GM dealership. It is identical to the stock thermostat with the exception of the springs not having the black coating on them. With the thermostat out, I then attempted to remove the driver side block drain. The breaker bar didn't budge it so I touched it with my air impact at 80 psi. Nothing. Cranked the pressure up to 120 psi and still nothing. Looks like that sucker is there to stay!

    Since I couldn't get the driver side block drain out, there was really no sense in screwing with the one above the starter on the passenger side. I installed the empty thermostat housing back on the water pump and clamped on the lower hose. I then pulled the top radiator hose at the radiator inlet. Removing my spray head, I inserted the garden hose into the radiator inlet and turned on the water. After flushing it for a few minutes, I then started the engine and turned on the heater and let it flush for another 2-3 minutes until the water started to run out warm. I stopped, waited about 10 minutes and then repeated this process. I could see the Dexcool for about the first minute or so and then it ran clear. Dare I call the engine properly "flushed" at this juncture?

    It looks like there are a few other hoses that I don't have yet and will have to inspect. I am replacing the upper and lower radiator hoses, the long thin air bleed hose and the split hose assembly that runs to the overflow bottle. The heater hoses appear to be quick connects and I am not sure if these should be replaced at this juncture or if they have a longer life than a normal hose assembly. Recommendations? The whole cooling system appears to have been plumbed by Chef Boyardee and is not as simple as the one on our Trans Am.

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    Looks like you are keeping busy. Can't say much for the heater hoses but your chef boyardee comment made me laugh

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    Your dealership guy konigandy6's Avatar
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    We hook up to the upper and lower hoses and use a power flushing machine...
    Smittro likes this.

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    You guys ain't helping much...


    The block drain has me stymied -- being a 17 mm allen head it is a beefy hunk of steel. GM probably should have stuck with brass plugs like on our Trans Am. I can't fathom why my impact wouldn't break it free. We have well water that is on the hard side and I want to try to displace as much of it as I can in the block since I used the hose to flush it. I am going to dump it full of distilled water and then while pouring more in start it up and hope it circulates enough to expel it.

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    Quote Originally Posted by pajeff02 View Post
    You guys ain't helping much...


    The block drain has me stymied -- being a 17 mm allen head it is a beefy hunk of steel. GM probably should have stuck with brass plugs like on our Trans Am. I can't fathom why my impact wouldn't break it free. We have well water that is on the hard side and I want to try to displace as much of it as I can in the block since I used the hose to flush it. I am going to dump it full of distilled water and then while pouring more in start it up and hope it circulates enough to expel it.
    Red Lock-tite..

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    I am guessing it is the factory installed coolant and that the system has never been flushed as we have owned it for 2 years now. It only had 61,500 on it when we bought it. If I recall, the plug in the Trans Am didn't have anything on it from the factory.

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    Quote Originally Posted by pajeff02 View Post
    I am guessing it is the factory installed coolant and that the system has never been flushed as we have owned it for 2 years now. It only had 61,500 on it when we bought it. If I recall, the plug in the Trans Am didn't have anything on it from the factory.
    had to have some sort of sealer on it.

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    I would have thought so too, but I am pretty sure the threads were bare. I used blue joint compound on both plugs when I reinstalled them.

    Looks like the Suburban's heater hoses require a special end that did not come with the replacement hose. Going to surf and see if I can find them now.

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    Wow, that would scare the shit out of me taking an impact to that plug.

    Run a flushing solution through the cooling system, perhaps one that is methanol based. Go drive it around with that in the system... a good 10-15 miles. Then flush it out real good and use the distilled for a final fill.

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    The books for both the Suburban and Trans Am recommend that a chemical flushing agent NOT be used. The old coolant, as well as the passages that I could see in the water pump and radiator all looked great with no buildup or other smegma. The block drain plug is quite large and made of steel, so no worries. Distilled water is a must and I performed a final flush last night with it to displace the remaining "household water" out of the system.

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    I was finally able to find and order the correct heater hose ends this evening. Turns out the fittings are T'ed due to the truck being equipped with rear heat and AC. There was very little room to work, I ended up pulling the transmission dipstick and unclipping a wire harness from the firewall to get my hands back in there while laying over top of the radiator support.








    This is the lower hose drilled and stuffed with a spray bottle tube so I could control the coolant draining process and not make a huge mess (yes, there be some surface rust on the undercarriage -- the stock GM frame coating really sucks):



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    Quote Originally Posted by 5.0THIS View Post
    Wow, that would scare the shit out of me taking an impact to that plug.

    Run a flushing solution through the cooling system, perhaps one that is methanol based. Go drive it around with that in the system... a good 10-15 miles. Then flush it out real good and use the distilled for a final fill.
    Err,, he'll be alright as long as he don't put in back in with an impact gun.

    OP: It's a truck Jeff it's supposted to be dirty..

    Well unless of course it's an H3..

    I enjoy seeing your work Jeff, you make many of these projects look easy..

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    Quote Originally Posted by pajeff02 View Post
    The books for both the Suburban and Trans Am recommend that a chemical flushing agent NOT be used. The old coolant, as well as the passages that I could see in the water pump and radiator all looked great with no buildup or other smegma. The block drain plug is quite large and made of steel, so no worries. Distilled water is a must and I performed a final flush last night with it to displace the remaining "household water" out of the system.
    I think that has more to do with not mixing a flush component with the dexcool. It may not have been an issue for you since you had all of the coolant out, and would flush out all of the flush component afterwards. Either way as long as it is clean, and it sounds like it is.

    Quote Originally Posted by Smittro View Post
    Err,, he'll be alright as long as he don't put in back in with an impact gun.
    I tend not to use an impact on anything that threads into aluminum, period. If it isnt budging, where is all of that force going? Straight into the block and threads. I've seen someone break aluminum casting while backing something out with an impact. Just not something I'd try

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    Understood. I normally don't use my impact on anything other than suspension components and big stuff. I just really hate to do a half-ass job by not being able to drain the block properly, so I elected to at least give it a try. Besides, if I broke the block it would give me a legitimate excuse to upgrade to a 6.0.
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    Quote Originally Posted by 5.0THIS View Post


    I tend not to use an impact on anything that threads into aluminum, period. If it isnt budging, where is all of that force going? Straight into the block and threads. I've seen someone break aluminum casting while backing something out with an impact. Just not something I'd try
    I see what you're saying for sure..

    I've had aluminum parts crack on it's own from corrosion/oxidization encrotching a bolt hole with the bolt in place.

    But I think as long as someone does'nt hold it there banging away it'll be okay,

    after all they get assembled on the line with pneumatic tools.

    Besides the explosions that take place right next door..

    May be able to hit it with some light heat and break it free just don't cook it,,

    as we all know how aluminum likes being over heated..lol
    Last edited by Smittro; 06-16-2012 at 08:52 AM.

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    Had to top off the reservoir twice since the flush and after 1,000 or so miles, all is well. I think that purchasing heater hoses from the dealership is the way to go. I am actually short two connectors at the firewall -- I attached the hoses directly to the T-fittings. There is supposed to be yet another quick connection there, but so far all has been fine.


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